Biological Assessment Guidance for Dredged Material - PIANC USA

Finally, we thank Ms. Janean Shirley of the U.S. Engineer Research and Development Center (USERDC)for editing the text of the report. Mr. Al Kennedy researched and prepared tables and graphics for thedocument and provided valuable editorial assistance to the chairman.Members of PIANC EnviCom Working Group 8Chairman:Dr. Todd S. BridgesU.S. Engineer Research and Development CenterWaterways Experiment Station, EP-R3909 Halls Ferry Rd. – Vicksburg, MS 39180-6199USATel 601-634-3626Todd.S.Bridges@erdc.usace.army.milVice-Chairman:Dr. Joost StronkhorstNational Institute for Coastal and Marine Management/RIKZP. O. Box 20907, 2500EX The HagueThe NetherlandsTel 0031-70-3114377j.stronkhorst@rikz.rws.minvenw.nlMembers:Estelle BjørnestadHead of LaboratoryDHI - Water and Environment11, Agern AlléDK-2970 HørsholmDenmarkTel 45-4516-9308esb@dhi.dkMr. Jose L. Buceta MillarCentro de Estudios de Puertos y CostasAntonio Lopez 81 - 28026 MadridSpainTel 0034 91 335 7676Jose.L.Buceta@cedex.esDr. T. Angel DelValls CasillasPhysical Chemistry DepartmentMarine Science FacultyUniversity of CadizPoligono Rio S. Pedro s/n11510 Puerto Real, CadizSpainTel 34-956-016044angel.valls@uca.es3

Dr. Tomohiro KuwaeCoastal Ecosystems DivisionPort and Airport Research Institute3-1-1, Nagase, Yokosuka, 239-0826JapanTel: 81 468 44 5046kuwae@ipc.pari.go.jpDr. Vera MaaßWirtschaftsbehorde HamburgStrom-und HafenbauIng. Buro Baggergut-UmweltangelegenheitenDalmannstr.1-420457 HamburgGermanyTel 040/42847-2826Vera.Maass@HT.Hamburg.deMr. Alberto MaffiottiARPA PiemonteVia della Rocca 4910141 TorinoItalyFax: 0039 11 6633274a.maffiotti@arpa.piemonte.itDr. Lindsay MurrayCEFAS LaboratoryRemembrance AvenueBurnham on CrouchEssex CMO 8HAU.K.Tel: +44 (0) 1621 787235l.a.murray@cefas.co.ukMs. Linda PorebskiEnvironment CanadaPlace Vincent Massey351 St. Joseph Blvd., 12 FloorGatineau, Quebec K1A 0H3CanadaTel 819-953-4341Linda.Porebski@ec.gc.ca4

B. IntroductionScopeThis report provides guidance to water resource managers, scientists, and engineers worldwide on theuse of biological testing to evaluate the potential hazards posed by contaminated sediments, in thecontext of navigation dredging (Figure 1). We concentrate here on the use of biological tests to developinformation to be used in making decisions about managing dredged material within the aquaticenvironment. The report describes the use of state-of-current-practice methods for assessing sedimentassociatedcontaminants through the use of acute and chronic toxicity tests and bioaccumulation tests,and refers to state-of-the-art tools evolving out of current research. We do not attempt to cover the wholeassessment/management process, but only those situations in which contaminants might be present andwhere information to define the potential for toxic effects will be useful in making management decisions.The generic, tiered approach described within this guidance is for assessing material for navigationdredging. Although the principles and approaches could be adapted for other uses, this guidance dealsonly with assessing whether a dredged material is suitable for open-water disposal and does not addresshow one would accomplish the more complex comparative analysis of management options that wouldbe required for decisions at remediation or cleanup projects.Figure 1.Sediment being collected for sediment toxicity testing using a Van Veengrab in New York Harbor, U.S. Navigation dredging activity is visible in thebackgroundInternational PerspectiveThe disposal of dredged material in the marine environment is covered by a number of global andregional conventions including the London Convention 1972 (LC, www.Londonconvention.org), theOslo/Paris Convention (OSPAR, www.ospar.org), and the Helsinki and the Barcelona Conventions.5

Guidelines developed from these conventions have incorporated biological testing intoassessment/management frameworks for dredged material; for example, the Waste Specific Guidelinesfor Dredged Material of the London Convention, (LC 1996 protocol). PIANC guidance (1998) onmanaging aquatic disposal of dredged material provides a tiered assessment and management approachin which dredged material is characterized in terms of its physical and chemical properties and the risksof biological impacts at the disposal site.Scientific consensus has been reached on the utility of biological testing to characterize the potential foradverse biological impacts associated with contaminated sediments (Programme of Global Investigationof Pollution in the Marine Environment (GIPME), 2000; Wenning et al., 2005). Considerable experienceand knowledge have developed in recent years concerning sediment assessment and a plethora ofexperimental approaches have been applied to evaluating sediments (Ingersoll et al. 1997, WaterEnvironment Federation 2002, Wenning et al. 2005). This report aims to draw from international bestpractice in dredged material assessment to derive practical guidance for managers, and to give pointersto future developments in the area of sediment assessment and management.The Need for Biological TestingDredged material is a chemically and physically complex matrix. This complexity places limitations on theuse of chemical analytical methods for estimating the bioavailability and toxicity of contaminants presentin the material. Biological testing is widely accepted as a method for characterizing the chemical hazardsin sediment and for providing information to support the management decision-making process. Byexposing relevant organisms under controlled conditions to samples of the actual material to be dredgedand measuring either toxicological effects (e.g., mortality, reduced growth) and/or the bioaccumulation ofcontaminants into tissues, the potential for adverse effects can be estimated. Biological tests provide ameans for assessing contaminant bioavailability as organisms are only expected to respond to thatfraction of sediment-associated contaminants that can be desorbed from sediment particles and broughtinto contact with organism tissues. Toxicity tests also serve an important integrative function given thatadverse effects in organisms are caused by the cumulative influence of each bioavailable contaminant.Predicting the cumulative influence of even the simplest contaminant mixtures from chemicalconcentration data poses serious challenges, given our current understanding of ecotoxicology. For theseand other reasons discussed in the text of this document, biological testing is considered a necessarycomponent of comprehensive sediment evaluation frameworks.A Framework for Biological Assessment of Dredged MaterialThe complexities inherent to sediment quality assessment necessitate relying on multiple lines ofevidence (LOE), within an overall weight-of-evidence (WOE) approach, to reach conclusions about thecontaminant risks posed. Assessment and decision frameworks based on WOE are designed to lead toconclusions that are founded upon a preponderance of evidence using information supplied from multiple,separate LOE, including physical, chemical, and biological data. In the context of a sediment assessment,separate LOE would be used to reach conclusions about potential exposure to and effects fromsediment-associated contaminants. Such an approach is commonly embedded within a risk-basedframework (Bridges et al. 2005). The development of such a risk-based framework specific for dredgedmaterial assessment is the subject of EnviCom Working Group 10. As stated previously, the guidanceprovided herein concerns the use of biological testing data within such an evaluation process.Evaluations of dredged material are most efficiently conducted following a tiered process that begins withsimple screening approaches and progresses to more detailed assessments where information frommultiple LOE is collected to reach conclusions about contaminant exposure, effects, and ultimately therisks posed by a dredged material. In applying this approach to dredged material assessment, aframework composed of three phases is proposed: Initial Assessment, Primary Assessment, andSecondary Assessment (Figure 2). The initial assessment phase begins by establishing goals for theassessment, developing a conceptual model for the project, and assessment questions and hypothesesthat will be tested during subsequent analysis. The primary assessment phase involves collecting existing6

information on the physical, chemical, and biological attributes of the material. During this phase of anassessment screening, guidelines based on the physical, chemical, or biological characteristics of thematerial may be used to reach early conclusions about the potential risks posed by the material. Ifmanagement decisions regarding sediment quality cannot be made with sufficient confidence usinginformation collected during the initial and primary assessments, direct measurements of toxicity and/orbioaccumulation will be made during a secondary assessment until sufficient information is available for aWOE decision about the potential risks posed by the material.7

C. Decision-making FrameworkFigure 2 presents the dredged material evaluation and decision-making framework developed andrecommended by Working Group 8. It provides a transparent and consistent process for designing anenvironmental evaluation that uses information from biological testing to reach an informed managementdecision. The framework includes iterative steps that help dredged material managers conductscientifically sound and cost-effective assessments.Secondary AssessmentInitialAssessmentPrimaryAssessmentRevise conceptual model/questionsDirect Water Column Effects•Water column toxicity testsDefine Project Scope•Establish project goals•Develop project conceptual model•Identify contaminants of concern•Identify resources of concern•Describe relevant exposure pathways•Define available management options•Develop assessment questions/hypotheses•Identify required LOEReview Existing Information•Physical•Chemical•BiologicalConduct Screening Assessment•Collect initial data•Compare to screening guidelines•Physical•Chemical•BiologicalDirect Benthic Effects•Solid-phase toxicity testsWOE decisionPlan and conductmonitoringIs the collected informationsufficient for a WOE decision?Is the collected informationsufficient for a WOE decision?Indirect Bioaccumulation Effects•Bioaccumulation tests•Interpretive tools and models•Risk assessmentFigure 2.Generalized assessment and decision-making frameworkFramework OverviewTo conserve time and other resources, the framework is tiered (Figure 2). Many government and portauthorities use a tiered approach that begins with collecting existing, relevant information, sedimentchemistry data, and results from “screening tests” followed by more detailed assessments whereappropriate.Following a tiered framework encourages focused sampling and analysis leading to credible anddefensible decisions. The process is iterative, with information from one tier guiding not only actionstaken in later tiers, but also informing, when necessary, reconsideration of conclusions made in previoustiers. Information generated by biological testing has a potential role in each of the assessment tiers inFigure 2.Initial assessment is largely a planning phase that establishes the overall goals of the project, defines aproject conceptual model, and develops the assessment questions that will focus the testing and analysisthat will be performed.The primary assessment phase uses relatively quick and inexpensive approaches to address theassessment questions. Existing data (e.g., previously conducted evaluations) and screening guidelines8

that are designed to identify obviously polluted or uncontaminated sediments are used to reachmanagement decisions regarding these materials in an expeditious manner.A secondary assessment follows when the primary assessment provides insufficient information toanswer the assessment questions within an acceptable level of uncertainty. The scope of the secondaryassessment is focused on the use of biological tests.Careful application of the framework proposed in this guidance will provide evidence upon which to baseconclusions about the presence/absence of hazardous contaminants and the potential for biologicaleffects at the proposed management site. Confidence in management decisions should increase as theWOE accumulated in favor of a specific conclusion increases. Following decisions and actions ondredging and open-water disposal, monitoring is needed to verify the adequacy of the assessment.Initial AssessmentDefining the Goals and the Scope of the ProjectClearly defined goals will drive and structure an assessment by clarifying what information needs to becollected during the assessment in order to facilitate decision-making. The framework assumes that thegeneral goal of the assessment will be to determine whether a dredged material, proposed for open-waterdisposal, is likely to cause adverse impacts at the disposal site. It specifically assumes that the regulatoryobjective is to prevent unacceptable adverse impacts on the environment (i.e., the receptors of concern).The framework being described here assumes that biological tests will be used to establish conclusionsabout the likelihood for adverse effects caused by contaminants if the material were to be placed at thedisposal site. If the management goal were simply to limit the introduction of contaminants into theaquatic environment, irrespective of the likelihood for an adverse impact, biological tests could provideinformation supporting the presence/absence of hazardous contaminants. Additional goals that may beserved by the assessment could include development of contaminant control strategies and studies ofsediment quality trends over time and/or space.Building a Project Conceptual ModelA conceptual model is a written description or graphical representation of predicted relationships betweenreceptors or resources in the environment and the stressors to which they may be exposed. A conceptualmodel represents a series of hypotheses about the processes bringing contaminants into contact withorganisms in the environment (Figure 3). Data collected during the course of the evaluation will be usedto test these hypotheses. A conceptual model is used by dredged material managers and assessors tohelp in defining the contaminants of concern in a project material, which sensitive organisms (e.g.,humans or ecological receptors) in the environment may be exposed to those contaminants, and whatexposure pathways may be operating to bring contaminants into contact with the receptors.Each dredging project will require a sediment-specific and setting-specific conceptual model. Thedeveloped conceptual model will provide the basis for managers and assessors to build a list of specificassessment questions that must be answered before management decisions can be made. A thoroughlydeveloped conceptual model provides an effective means of communicating to stakeholders andregulatory authorities that all the important processes of relevance to the decision have been consideredand accounted for in designing the assessment. For routine navigational dredging, some regulatoryauthorities may use standardized conceptual models, with associated assessment questions, that themanager and assessor are obliged to follow. Where no such model is available, the sections below guidethe development of a project conceptual model and assessment questions.9

Generalized Conceptual Model for a Dredged Material EvaluationSourcesSedimentProcessesAquaticReceptorsWildlife and HumanReceptorsAirPointSourcesStormwater& non-pointsources“Upstream”sourcesSpillsSubsurfaceNAPL FlowsBioturbationScouringDepositionResuspensionTransportSurface WaterSurface Sediment(BiologicallyActive Zone)DeepSedimentBurialFishBenthicInvertebrates--------PlantsWildlifethat eatfishWildlife thateatInvertebratesorPlantsHumansGroundwaterSorptionDesorptionDegradationFigure 3.From Bridges et al. (2005). NAPL = Non-Aqueous Phase LiquidsIdentifying Contaminants of ConcernScoping the assessment and building a project-specific conceptual model will require developing a list ofpotential contaminants of concern (COC) in the dredged material. In some jurisdictions, regulators mayprovide dredged material managers and assessors with a specific list of contaminants that are to beconsidered in the evaluation. In other cases, a list of COC may be developed independently for eachproject based on information about point and non-point sources of pollution around the dredging site.Historical information about industrial or agricultural activity in the area can be combined with knowledgeof current activities ongoing in proximity to the dredging site to produce a list of COC. Constructing a mapthat relates the proximity of a source (e.g., ongoing inputs like effluents or run-off or historic events likestorms or spills) to the likelihood that a contaminant may be present will be a useful aid in this process.Proximity to wastewater effluents, aquaculture or agriculture may also necessitate consideration ofbiological stressors (e.g. pathogens). Any existing chemistry data on sediment or water samples taken ator near the site of interest would aid in developing a list of COC.Physical information that could affect the presence of contaminants in the dredged material includes:• Specifics of the dredging project (depth of the dredging cut, dredging equipment, timing, etc.).• Hydrodynamic energy present at the dredging site (are contaminants likely to be transported to oraway from the site by storms, waves, currents, etc.?).• Geochemical properties of the sediment (e.g., sand is less likely to retain contaminants due tosmaller relative surface areas).• Site use patterns (navigation channels that are dredged regularly may accumulate fewercontaminants).10

Similarly, an evaluation of conditions at the disposal site, in terms of its bathymetry, ecology, geochemicalproperties, hydrodynamics, and previous use patterns should be considered in an effort toestablish which contaminants are likely to pose a hazard at the disposal site.Once chemicals or other stressors are identified, information about the physicochemical behaviour of thecontaminants will be used to develop a conceptual model that leads to appropriate testing. For example,PCBs generally pose a greater threat to higher trophic levels than they do to sediment-dwellingorganisms, as these compounds bioaccumulate and biomagnify in food chains. Where bioaccumulativechemicals are included in the list of COC, the assessment will need to address questions concerned withthe movement of these contaminants within the local food web and the potential for effects at uppertrophic levels. For most metals, with the notable exception of metals that form organic species (e.g.,mercury) direct toxicity to organisms coming in contact with the sediment would be the primary concernand tools/tests that predict or estimate likely toxicity should be selected to evaluate this potential(Section D).Identifying Receptors of ConcernThe potential receptors of concern (ROC) for a dredging project that proposes to use aquatic disposal willinclude invertebrates that live in sediment (i.e., infauna), animals and plants living on the sedimentsurface (i.e., epibenthic), bottom-associated (i.e., demersal) fish, pelagic fish and invertebrates, birds andother wildlife, and humans using the site (Bridges et al. 2005; Ingersoll et al. 1997). The list of ROC willdiffer among dredging projects depending of the size of the project, its geographic location, and theextent of exposure. Most navigation dredging assessments will give consideration to infaunal andepibenthic receptors as these groups of organisms experience direct exposures to deposited dredgedmaterial over both the short and long term. The need to examine the potential for impacts on otherreceptors will depend on project and site-specific factors including the extent of dispersion of the materialwithin the water column, the potential for movement after disposal, and the extent and nature of thecontaminants in the sediment.For example,• When sediment is expected to be present in the water column for long and continuousperiods due to the nature of the dredging operation or because of the frequency of resuspensionevents, it may be appropriate to include assessment questions and biologicaltests focused on the potential for effects of direct exposure on fish and other pelagic species.• Where sensitive receptors are present (e.g., threatened or endangered species) or wherecommercially valuable resources (e.g., oyster fisheries) could be impacted by a dredgingoperation, the scope of the assessment may be expanded to address the complexitiesinherent to these receptors.• In cases where the principal COC are compounds that are known to bioaccumulate andbiomagnify in aquatic food webs (e.g., PCBs, DDT, mercury) higher trophic-level receptors ofconcern (e.g., wildlife and humans) would be included in the conceptual model to focusattention during the assessment on the potential for effects on these sensitive receptors.Describing Relevant Exposure PathwaysThe term exposure pathway refers to the sum of the processes that bring a contaminant into contact witha receptor. Adverse effects at the disposal site are only possible if an exposure pathway for bringing thecontaminant into contact with a receptor of concern exists at the disposal site. Exposure pathways resultfrom a range of processes including current or wave-driven sediment transport and re-suspension,bioturbation, animal behaviors such as locomotion and feeding, etc. In addition, exposure pathways canbe created and/or influenced by planned dredging and disposal activities. Living resources can beexposed through contact with contaminants that partition into the water column, that are associated withthe bedded sediment or through trophic transfer within the local food web (Figure 4). Describing theseexposure pathways, either graphically or in narrative fashion, within the conceptual model will lead11

managers and assessors to identify which exposure pathways and receptors should be assessed andwhich biological tests are applicable for the assessment.Figure 4.This cartoon depicts different contaminants in the sediment environment,potential for uptake in the benthic community and trophic transfer to higherlevelorganismsIn most cases, it will not be possible to adequately assess all possible combinations of pathways,contaminants, and receptors due to limits in our understanding of the relevant processes and constrainedaccess to resources, time, and assessment tools. The assessor will need to exercise and defendprofessional judgements about priorities for the assessment. The scope of the assessment, which wouldinclude the extent to which possible exposure pathways are evaluated, should be scaled to judgementsabout the potential intensity, duration, frequency, or spatial extent of the stressor. For example, for anassessment being undertaken on coarse-grained material destined for a similar coarse-grained disposalsite, pathways associated with direct contact with sediment in the water column and the bottom will exist.However, water column exposures would be short-lived due to high particle settling velocities, limiting thepotential for significant effects. Assuming that contaminants are present in the material, it would bejustifiable to devote more resources to assessing the potential for effects associated with direct contactwith bedded sediment given the expected longer duration of exposures to deposited material.Available Management OptionsThe nature and design of a dredged material assessment will depend on the management options beingconsidered. Other PIANC documents discuss the details of various management options for dredgedmaterial (e.g., PIANC (1997)). In general, there will be two broad categories of options: aquatic andupland disposal. In both cases management decisions will include the selection of suitable dredgingequipment and techniques and the selection of a suitable disposal site. Considering the operationalelements of the project at the beginning of the assessment process allows an assessor to incorporatethese aspects of the project into the conceptual model so that germane assessment questions can be12

formulated for the anticipated operational scenario. For example, hydraulic dredging would likely suspendless sediment at the dredging site, unless hopper overflow is permitted, but would likely result in moresuspended sediment at the disposal site, than would mechanical dredging. Deep-water disposal sites thatare farther from shore, for example, will likely eliminate the need to assess potential impacts on plants orterrestrial wildlife thus simplifying an assessment.In cases where the conceptual model includes management options other than unrestricted open waterdisposal, biological testing may provide useful information for designing a management strategy. While itwould not be appropriate to use a sediment toxicity test to evaluate the potential for effects on upland,soil-dwelling invertebrates, such tests could be used to assess potential effects on aquatic receptors incases where the material would remain covered with water or there are concerns about impacts fromeffluent discharges into an adjacent water body. The use of biological tests appropriate for uplandassessments, in a manner similar to the aquatic evaluations presented here, are discussed in USACE(2002). Similarly, where confined aquatic disposal (i.e., the use of capping) is planned, broader questionsconcerning the extent and efficiency of physical confinement will be more relevant to decision-makingthan the toxicity of the material to be managed.Giving adequate attention to the development of a conceptual model for the proposed operation will helpto ensure that the assessment designed to address the environmental questions of concern will provideappropriate and sufficient information for decision-making. Simultaneously considering all of the potentialand feasible management options and collecting biological testing data for each, where appropriate,would provide the basis for comparing potential impacts among the alternatives. Such comparativeanalysis can provide for more informed and efficient decision-making (Kane Driscoll et al. 2002).Developing Assessment Questions/HypothesesDeveloping a conceptual model structured around the operational parameters of the project, knowncontaminant sources, the contaminants and receptors of concern, as well as representations of thephysical and biological processes influencing exposure and effects will lead managers and assessors todevelop a list of assessment questions. These questions describe the issues or concerns that must beaddressed; answers to these questions will provide input to decisions about how to manage the material.The specific questions to be addressed in a biological assessment will depend on the nature of applicablejurisdictional interests and regulations, the environmental setting where the dredging and disposal willoccur, as well as the complexity of the project, including the number of contaminants and receptors ofconcern. Example questions that may be posed by managers or regulators evaluating a proposed projectare provided in Table 1. This short list of questions is by no means exhaustive; however, it does illustratethe degree of specificity that should be targeted when formulating such questions. Specificity in thewording of assessment questions will facilitate the process of translating these questions into hypothesesthat can be tested using screening procedures during the primary assessment or in selecting appropriatebiological tests and interpretive criteria during a secondary assessment (presented in Table 2).The iterative nature of the assessment framework, represented by the arrows which lead an assessmentto a previous step or phase (Figure 2), was incorporated into the process in recognition of the fact that asan assessment proceeds and new information is collected, modifications may need to be made to theexisting conceptual model and assessment questions and hypotheses, or entirely new questions may berequired. Care should be taken to ensure that such iteration does not lead to an endless cycle of revisionand modification; however, in many projects some degree of iteration will be necessary.13

Table 1Examples Assessment Questions for a Navigational Dredging ProjectDirect Benthic Effects• Will the mix of contaminants present in this dredged material be toxic to freshwater sedimentdwellingfauna?• Will the polychaetes that dominate the fauna at my disposal site be adversely affected by thesediment-associated contaminants in this dredged material?• Will the crustaceans that dominate the fauna at my disposal site be adversely affected by thesediment-associated contaminants in this dredged material?• Will the neogastropod molluscs inhabiting the disposal site be adversely affected by the TBT in thisdredged material?• Are dioxin-like compounds present in this dredged material at levels of concern?Direct Water Column Effects• Will zooplankton be adversely affected by sediment-associated contaminants during barge disposalof dredged material at the management site?Indirect Bioaccumulation Effects• Will the fish that use the disposal site as a feeding ground be adversely affected by this dredgedmaterial?• Will fish-eating birds be adversely affected by placement of this dredged material at the disposalsite?• Will the health of recreational anglers fishing at the disposal site be endangered by the placement ofthis dredged material at the management site?One of the benefits of developing an explicit and formal list of assessment questions is that generatingsuch questions represents a useful planning step in an assessment where agreement can be reachedbetween a project proponent and regulatory authorities about what information will need to be collected toreach management decisions. By following the framework through the development of a conceptualmodel and associated assessment questions all stakeholders can reach a common understanding of thebasis of the assessment and the future management decision. It is important that this process andinteraction among stakeholders be documented at each stage of the assessment to ensure accountabilityamong those participating in the evaluation and decision-making process.Identifying Relevant Lines-of-Evidence (LOE)The concluding element of the initial assessment is to identify the LOE that will be used to reachconclusions about the nature of the dredged material and how it should be managed. While the natureand use of LOE is discussed in some detail in Section G, it should be noted here that the LOE’s that willbe used in decision-making are identified at the earliest phases of an assessment. This identification willinform subsequent choices about data needs and biological tests that will be used to develop theinformation set necessary to reach credible conclusions about the suitability of the material for aquaticplacement.Primary AssessmentReview Existing InformationFollowing development and agreement on the project conceptual model and the assessment questionsthat flow from it, a primary assessment will be conducted using existing or easily obtained informationabout the physical, chemical, and biological properties of the material.14

For most maintenance dredging, and even a good portion of new work or capital projects, previouslygenerated information relevant to the environmental evaluation will be available from a variety of sources.Engineering surveys conducted to plan a dredging project will produce information about the geographiclocation of the dredging site and potential disposal sites, the quantities of material to be dredged, thedepth of dredging, particle size distribution of the material as well as other geotechnical data (e.g.,percent water). Information that would be collected in this phase of the assessment would include data oncurrent uses of the water body and surrounding land. Previous dredging or research projects in the areamay be sources of data on contaminant concentrations, the presence of previous toxicity in the sedimentor water column and receptors of concern in the project area. When using existing information, however,care should be taken to assess the relevance and the suitability of the data. Data that are several yearsold and that were generated under unknown conditions of quality control/quality assurance, or datacollected prior to a change in site conditions (i.e., changes in pollution sources, spills, major storms, etc.)will be of limited value in evaluating the material. Existing publications provide guidance on sources anduses of existing information at the beginning phases of a dredged material evaluation (USEPA/USACE1991, 1998).The purpose of the primary assessment is to use existing or easily collected information to determine,based on minimal investment in data collection, whether open-water disposal would be clearlyappropriate or inappropriate, or whether additional information would be needed before reaching such adetermination. The assembled data are examined with reference to the conceptual model andassessment questions. If the assessment questions can be satisfactorily answered using existing data,with an acceptable degree of confidence, then the evaluation can be concluded and the appropriatemanagement decisions made. For example, if the sediment to be dredged is spatially remote frompollution sources, is composed predominantly of coarse-grained sand particles, or hydrodynamicconditions at the disposal site are such that the material would be expected to remain at the site, thenthese lines of evidence could support a determination that there is a low potential for causing adverseeffects during or after disposal. In another case, where the navigation channel is located in a highlyindustrialized setting, previously collected chemistry data indicate high levels of several contaminants,and biological tests performed on material from the site over the past several years have consistentlydemonstrated the presence of unacceptable toxicity, it may be reasonable to conclude that additionalevaluation is not warranted and that the resources that would have been spent on additional assessmentcould be better applied to evaluating alternatives to open-water management.In all but the rarest of cases management decisions, even at the stage of a primary assessment, will bebased on multiple LOE’s (see Chapter G for further discussion of lines and weight of evidence). SeveralLOE’s should be used as a basis for decisions at the early stages of an assessment because the costs ofmaking an incorrect conclusion can be high. This is particularly true for a decision allowing open-waterdisposal without further detailed testing, as an incorrect decision could result in serious environmentalimpact.In cases where the existing information is judged to be insufficient for decision-making, the collected datashould be reviewed with respect to the project conceptual model and assessment questions to evaluatethe need for making any modifications to these elements of the assessment and to identify specific datagaps that should be satisfied during further evaluation. Such a data gap analysis may result in thedevelopment of a sampling plan that can be used to guide the collection of additional data duringsubsequent primary and secondary assessment activities in a technically defensible, cost-effectivemanner.Conduct a Screening AssessmentIn this phase of the assessment, relatively inexpensive and rapid tests are conducted to focusassessment effort on those cases where uncertainty about potential exposure and effects is greatest.Limited sediment sampling and data collection may be performed at this stage for the purpose ofcomparing the project sediment to physical, chemical, or biological screening guidelines which aredesigned to enable managers and assessors to reach confident conclusions that the material is eitherhighly unlikely or highly likely to cause adverse biological impacts at the disposal site.15

Physical GuidelinesThe physical composition of the dredged material is one of the most obvious and easily collected piecesof information that can be used to reach conclusions about whether that material could be sufficientlycontaminated to pose a hazard to the environment. Dredged material composed predominantly of coarsegrainedmaterials (e.g, rock, cobble, and sand) have a low potential to carry significant amounts ofchemical contaminants because of the relatively small surface area available for sorption of contaminantsper unit volume of material. Based on past experience, regulatory authorities may set quantitative orqualitative guidelines to define when sediment will be judged to be predominantly composed of suchcoarse-grained material. Other physical LOE’s that can be used in combination with the geotechnical datato reach a conclusion that the material is unlikely to pose a chemical hazard would include the depth ofdredging (e.g., will the material be dredged from sediment horizons that have had no contact withindustrial chemicals) and geographic proximity to known or suspected sources of contaminants.Chemical GuidelinesChemical benchmarks, such as chemical sediment quality guidelines (Wenning et al. 2005), can be usedto gauge the degree to which a sediment is contaminated with chemicals and to estimate thepotential/probability of unacceptable biological responses in organisms that would be exposed to thatsediment (i.e., toxicity to benthic invertebrates). Such sediment benchmarks, referred to by various terms(e.g., values, standards, criteria, guidelines, action levels, etc.), have been used by jurisdictions in manydifferent ways to achieve a range of purposes (Berry et al. 2005), including use as rough gauges andfixed regulatory levels. The definition and meaning ascribed to these benchmarks vary acrossjurisdictions; a manager or assessor using them should verify not only their narrative intent (what they areintended to predict) but the level of confidence or caution that developers or users have attached to theiruse. Those choosing to use chemical guidelines should be aware of how the guidelines were derived(whether they were intended to predict toxicity or the absence of toxicity) and what effects (if any) theywere designed to assess.There are two main approaches to deriving effects-based, chemical sediment quality guidelines. Themechanistic approach is based on a calculation of equilibrium partitioning between a bound phase and adisassociated phase within pore water (Di Torro et al. 1991). Empirical approaches to deriving sedimentquality guidelines are based on statistical analyses of co-occurring chemical and biological effects data inwhole sediments (Long et al. 1995; Riba et al. 2004; Wenning et al. 2005). The former approach may bebetter suited to providing guidelines for predicting the presence of effects where a single contaminantpredominates in the sediment, while the latter approach has been used to produce guidelines that aremore suited to predicting the absence of acute toxicity in sediments where there is a mixture ofcontaminants. The narrative intent of lower-level empirical guidelines (e.g., ER-L) is to predict when acutetoxicity is unlikely to occur. Error rates associated with these guidelines are on the order of 10-20 percent.The upper empirical guidelines (e.g., ER-M) are intended to indicate when an increased probability ofobserving toxic effects is evident, as the number of individual upper level guidelines exceeded increasesthe likelihood that the sediment is toxic increases. The accuracy and reliability associated with theapplication of both types of guidelines is a matter of ongoing discussion in the scientific community(Wenning et al. 2005). Some of this debate has focused on definitions of what constitutes acceptable orunacceptable effects or even how effects should be defined.Recent work has focused on developing quotient methods, which are derived by summing the “toxic”contributions of a number of contaminants of concern (Wenning et al. 2005). Regression analysis thatallows for considering effects from several contaminants at once along a continuum of concentrations hasalso been developed (Field et al. 2000).The development of sediment quality guidelines and approaches for applying them in decision-making(e.g., see Bridges et al. (2005)) is a rapidly evolving area in the field of sediment assessment. Someconsensus currently exists for using lower-level guidelines, in combination with other LOE (e.g., physicaland biological data) to reach a conclusion that a material poses a small likelihood for causing adverse16

effects of the type considered by the guideline. In cases where lower and upper sediment qualityguidelines are exceeded, direct toxicity tests are usually applied as an additional LOE for use in decisionmaking.The use of biological tests in this regard is discussed under “Secondary Assessment” below andin subsequent sections of this document.It should be noted that not all numerical chemical benchmarks are effects-based (i.e., predict thelikelihood for effects). Many sediment benchmarks in use worldwide represent simple measures ofnatural background conditions or some measure of ambient contaminant concentrations that are judgedto be acceptable based on a policy goal or to satisfy economic concerns.At a minimum, the selection and use of chemical sediment benchmarks and guidelines should be basedon:• Meeting existing regulatory requirements;• Matching the assessment question with the narrative intent of the guideline (e.g., guidelines predictingan absence of direct toxicity to benthic organisms provide no information about effects mediatedthrough bioaccumulation to upper trophic levels);Biological Screening GuidelinesThe third LOE that can be used during a screening assessment is the application of biological informationapplicable to the assessment questions posed during the initial assessment. A number of in vitro methodsthat make use of cultured cell-lines to test sediment or extracts of sediment have potential utility during ascreening-level assessment. Some of these biomarker tests are discussed in more detail in Section H.These tests can be used to address concerns about the presence of chemicals that may not have beentargeted in initial chemical analyses or to target particular kinds of compounds (as discussed in SectionH). Limited and targeted application of biological tests applied more commonly during a secondaryassessment might also be used at this stage of an assessment to resolve uncertainties remaining afterconsideration of the physical and chemical LOE. Simple modelling approaches such as the use ofcalculations of theoretical bioaccumulation potential can also be used to address questions concernedwith bioaccumulation of non-polar organics (e.g., PCBs) (see Section D).GIPME (2000) suggests that because of the expense and time involved in conducting biological testing, itis advisable to learn as much as possible about the presence of hazardous conditions in a sediment fromevidence collected from the field before laboratory testing is considered. Simple observations of animaland plant assemblages resident at the dredging site that are made using grab sampling, diver surveys, orunderwater photography can help in characterizing sediment quality. Even simple techniques can detectevidence of major problems in a proposed dredged material. It should be noted, however, that it is notalways straightforward to establish a linkage between observations of in situ biological conditions and thepresence of a chemical stress. Physical disturbance created by navigation traffic or storms andenvironmental conditions leading to periods of anoxia will influence the composition and structure ofbiological communities at a site. For this reason, field-based observations will not always be appropriatefor navigation dredging assessment, although they may be useful for obtaining baseline data on a newdisposal site prior to disposal or for disposal site monitoring (See Section D on measuring exposure andeffects in the field).Conclusions of the Primary AssessmentAt the conclusion of the primary assessment, a judgement will be reached as to whether the collectedinformation is sufficient for reaching a WOE decision. If each of the assessment questions formulated atthe conclusion of the initial assessment can be confidently addressed using the LOE developed duringthe primary assessment, then the evaluation can be concluded and appropriate management decisionscan be made. If, however, the evidence assembled thus far in the evaluation is judged to be insufficient toreach a credible conclusion about the potential for adverse impacts at the disposal site, then theevaluation would continue into a secondary assessment. It should be emphasized that even at this early17

Table 2Example assessment hypotheses and biological tests derived from the assessment questions inTable 1Direct Benthic Effects• The 10-day survival of Hyallela azteca and Chironomus tentans will not be significantly different indredged material when compared to reference sediment as conducted using ASTM (2000a) or USEPA (2000b)• The survival and growth of Neanthes arenaceodenata will not be significantly different in dredgedmaterial when compared to reference sediment as conducted using ASTM (2000b)• The survival and growth of Ampelisca abdita will not be significantly different in dredged materialwhen compared to reference sediment as conducted using USEPA (1994) or ASTM (1999, 2003c)• The vas deferens sequence index will not be signfiicantly different in gastropods exposed todredged material compared to a reference sediment following Oehlmann et al. (1991).• Dioxin-like activity in the Calux assay will not be detected in the dredged material at levels greaterthan the reference as conducted using RIKZ (2000d).Direct Water Column Effects• The LC50 concentration of dredged material elutriate for sea urchins will not be significantlydifferent than the reference as conducted using US EPA (1990).• The LC50 concentration of dredged material elutriate for ostyer larvae will not be significantlydifferent than the reference as conducted using ASTM (2004).Indirect Bioacumulation Effects• Bioaccumulation of sediment-associated contaminants will not be significantly different in dredgedmaterial and reference exposed Macoma nasuta as conducted using Lee (1993). 1• Bioaccumulation of sediment-associated contaminants will not be significantly different in dredgedmaterial and reference exposed Nereis virens as conducted using Lee (1993). 1• Bioaccumulation of sediment-associated contaminants will not be significantly different in dredgedmaterial and reference exposed Lumbriculus variegatus as conducted using USEPA (2000b).1 A significant elevation in contaminant tissue concentrations in test organisms exposed to dredgedmaterial does not necessarily mean that risks to upper trophic levels are likely. A definitivedetermination that the concentrations observed would pose a risk would require further analysis (e.g.,trophic transfer modeling and dose calculations). However, it is reasonable to conclude from a failure tostatistically distinguish the dredged material and reference exposed organisms that risks to uppertrophic levels are unlikely.Conclusions of the Secondary AssessmentAt the conclusion of the secondary assessment, a judgement will be reached using the collected,organized and analyzed biological data as to whether the material would likely produce an adverseimpact if it were to be discharged into the environment (e.g., during open-water disposal operations). Thisjudgement will be made based on the WOE collected. If the assembled data are judged to be insufficientfor decision-making (i.e., significant uncertainties remain) then the evaluation would continue untilsufficient evidence is collected to reach a credible conclusion. The evaluation would continue byconsidering the adequacy of the project conceptual model and assessment questions and by identifyingthe need to conduct additional data analysis or testing. As was true for conclusions reached during theprimary assessment, secondary assessments will involve consideration of multiple LOE.Support for a specific conclusion will be strengthened as each line of evidence leading to that conclusionis developed and substantiated. As additional LOE are added in support of a conclusion, confidence inthat conclusion grows. The challenge of using approaches based on developing multiple LOE to reach19

conclusions based on the weight, or preponderance, of evidence is that occasions arise when the lineslead to more than one conclusion. This issue is discussed in more detail in Section H; however, theexistence of this challenge emphasizes the need for developing decision rules for analyzing and drawingconclusions from the data prior to conducting the tests. Even so, professional judgement, based on prioragreements reached among regulators, dredged material managers, and assessors is a commonelement of effective decision processes.In the selection and use of biological tests, one should bear in mind that the decision to use each testcarries with it a set of uncertainties that could affect the “weight” (or degree of emphasis) that an assessormay assign that test in reaching conclusions about the potential for impact. Ingersoll et al. (1998) rankedthe relative uncertainty associated with various tests and test endpoints, giving the lowest uncertaintyrank (i.e., highest confidence rating) to whole sediment benthic tests followed by whole sediment watercolumn tests and those based on various extracts of sediment. For test endpoints, the lowest uncertaintywas assigned to measures of survival, followed by growth, reproduction, behaviour, demography,development and various biomarkers. These rankings reasonably reflect the consensus as regardstoxicity testing in general; however, the uncertainty associated with a test, or set of tests, will varydepending on how the tests are applied to address a specific set of project-related questions. Both testselection and uncertainty are further discussed in sections D and H, respectively.MonitoringAfter a dredged material has been subjected to an environmental evaluation, a decision has beenreached about how to manage that material, and the selected management alternative has beenimplemented, monitoring should be conducted in order to:• Verify that the assessment questions were correctly answered.• Identify any problems at the disposal site.• Provide feedback to the assessment process.• Identify research gaps and areas where a better understanding of system processes would improvedecision-making.A monitoring plan/design will be developed to guide monitoring activities at the site. The monitoring planshould be developed using information collected during the evaluation process so that assessment datacan be used to formulate the questions (e.g., impact hypotheses) to be pursued in the monitoringprogram. An effort should be made to review all existing assessment data relevant to a specific site whendesigning the monitoring program. Biological testing can be used as a tool during disposal site monitoringin much the same way it is used in the assessment phase. Monitoring is discussed further in Section I.20

D. Types of Biological TestsOver the last several decades, the effects of chemicals on living systems have been intensively studiedexperimentally by measuring adverse biological responses in organisms following exposure tocontaminants. Biological tests have evolved from this wide-ranging study of environmental toxicology astools that can be used to inform decisions regarding the environmental management of chemicals ormaterials contaminated with hazardous substances, as in the case of dredged material.A biological test is an experimental procedure or method that makes use of a biological system (e.g.,whole organisms, tissues, cells) to provide information about chemical exposure or effects (Figure 5).Numerous tests have been developed and used to study exposure and effects of chemicals in water andsediment. These tests vary in their relevance to particular biological receptors of concern, the endpoint ofconcern, and exposure pathways by which contaminants may come into contact with those receptors.Figure 5.Cartoon depicting a biological test in which test organisms are exposed to asediment in a controlled experimental systemReceptors of concern will come in contact with contaminants in dredged material through one of threeprimary exposure pathways: 1) through contact with bedded sediment particles, 2) through contact withwater that is contaminated via the sediment, and 3) through contact with contaminants throughbioaccumulation and trophic transfer within a food chain (Figure 6). Tests will need to be applied toaddress assessment questions associated with these various pathways.21

1) Sediment ingestion2) Bioconcentration viacontact with contaminatedwater/sediment3) Bioaccumulation via consumption of other exposed organismsFigure 6.Mechanisms of exposure of aquatic animals to contaminantsBiological tests may provide either measures of effect or exposure, or in some cases both. Laboratoryand field-based methods are available for generating information about the potential for effects andexposure. Tests that provide measures of effect provide information about the hazard or toxicity of thedredged material by measuring adverse responses in organisms exposed to the material. Laboratorybasedtoxicity tests are commonly used in dredged material evaluations. Methods for measuring effects inthe field are also appropriate for some case-specific applications. Such field methods includemeasurements of benthic community structure or observation and measurement of effects on individualorganisms (e.g., cancer in resident fish). Other biological tests provide information about exposureconditions including measures of the bioavailability of the contaminants present in dredged material or theconcentration or dose received by the receptor. Bioaccumulation tests, which measure the movement ofcontaminants into the tissues of the test organism, are the most commonly applied biological tests forcollecting information about exposure.Measuring Exposure and Effects in the Field: Linking the Data to the SedimentCollecting data directly from the field site of concern can provide useful information for managingcontaminated sediments. Surveys of benthic community structure that collect taxonomic data on thenumber and types of species resident within a spatially defined area of sediment can be used to describethe status or condition of the benthic environment (Figure 7). However, making causal linkages betweenthe observed status of the benthic community and the presence of chemical contaminants in thesediment can present a number of challenges. For example, navigation channels are subject to varyingdegrees of physical disturbance due to the movement of ship traffic; such disturbance can be reflected inthe taxonomic structure of the benthic community. For this reason, information about benthic communitystructure alone offers limited value in judging the need for special handling or management once thesediment is dredged from the channel. Information about benthic community structure has been usedextensively as a part of monitoring programs at dredged material disposal sites; however, effective use ofthis information also requires distinguishing effects due to the physical disturbance created by a disposalevent versus effects caused by the presence of chemical contaminants (Section G).22

Figure 7.In-place sediment at a field site using sediment profile imagery. Tubes andother biogenic structures evident are typical of many benthic environmentsMeasuring exposure or effects on individuals inhabiting a dredging or disposal site can provide usefulmanagement information depending on the degree to which the organism is spatially connected to thesite. Tissue samples collected from organisms living in, on, or above the sediment can provideinformation about potential exposure through bioaccumulation of contaminants present in the sediment.The degree to which measured tissue concentrations of contaminants in field-collected organisms can beinferentially linked to the sediments at the site of concern depends on the extent to which the organismreceives exposure from the overlying water column and the mobility of the organism. Animals with highmobility (i.e., having a large “home range”) can be expected to reflect exposure conditions over a largerarea, perhaps much larger than the area occupied by the sediment of concern in a specific evaluation,than organisms with limited mobility. Effects have also been measured in field-collected animals. Thepresence of tumors in field-collected fish is the most widely used measure of toxicological effects in fieldsettings. Such measures can provide valuable information that can be difficult, impractical, and evenimpossible to collect under laboratory exposure conditions given the length of time required for exposuresto result in cancer formation. The challenge, again, for typical navigation dredging applications is inlinking the individual fish to the sediment of concern.Experimental (i.e., manipulative) approaches for measuring bioaccumulation and toxicity in situ have alsobeen applied to the assessment of sediments. This approach involves confining either field-collected orlaboratory-cultured animals within field-deployed containers in or on the sediment of concern (Figure 8).The advantages of this approach over laboratory-based tests are: (1) enhanced ecological relevance(i.e., exposure is more reflective of actual site conditions, (2) direct linkages between exposure andeffects, and (3) lower relative day-to-day test maintenance. However, in situ approaches are morelogistically complicated to execute given the complexities inherent to field-based experimentation (e.g.,storm events, predation, fouling). Research on the development and application of in situ methods offerspromise for a broader role for this approach in the future.23

ERDC-EL, Vicksburg, MSERDC-EL, Vicksburg, MSApplied Biomonitoring, Kirkland, WAERDC-EL, Vicksburg, MSFigure 8.Examples of field deployments of clams used for in situ biological testing.In situ biological tests have also been successfully conducted using fish andother macroinvertebratesMeasuring Exposure and Effects in the Laboratory: Matching Biological Tests With ExposurePathwaysThe most commonly applied approach for collecting data necessary for making management orregulatory decisions about dredged material involves collecting the sediment from the dredging site andtesting it under laboratory conditions. The selection of which laboratory tests to include in the assessmentbattery will be determined by the pathways, receptors, and assessment questions that are relevant for thespecific project under consideration.Solid-Phase Toxicity Tests: Questions regarding the potential for contaminants in dredged material toproduce adverse effects in organisms closely associated with deposited sediments can be addressed byusing solid-phase toxicity tests. The setup for a typical sediment toxicity test is shown in Figure 9. Thesetests involve exposing test organisms to bedded sediments for a defined period and measuringresponses in those organisms (e.g., rates of survival, growth, reproduction) at the conclusion of the test.To ensure that test results will be protective, with respect to the exposure conditions expected at amanagement site, the species used in such tests should be selected based on their close behavioralassociation with the sediment and their sensitivity to contaminants. Organisms that live in and/or ingestsediments (e.g., infaunal invertebrates) are expected to have high exposure to sediment-associatedcontaminants due to their intimate contact with sediment particles and pore water. Tests using infaunalamphipods, polychaetes, bivalve molluscs, urchins, and other taxa have been developed and commonlyapplied to assess dredged material (Figures 10 and 11).24

Figure 9.Typical sediment bioassay receiving aeration in a temperature andphotoperiod controlled environment chamber, with addition of overlyingwater (upper right) and test breakdown (lower left)Leptocheirus plumulosusCorophium spp.Neanthes arenaceodentata Ampelisca abditaFigure 10. Estuarine and marine species commonly used in sediment toxicity tests25

Chironomus tentansHyallela aztecaTubifex tubifexFigure 11.Freshwater species commonly used in sediment toxicity testsRecognized differences among candidate test species in terms of their behavior within sediments haveresulted in broad consensus on the need for testing using multiple species. Some taxa actively burrowthrough sediments, while others live within semi-permanent burrows or even tubes they construct withmucus and sediment particles. Some species actively ingest sediment particles while others rely more onremoving particles from suspensions in the overlying water. Species with these different behavioralcharacteristics will experience different exposures to contaminants adsorbed to sediment particles ordissolved within pore waters. Selecting a battery of tests that represents this diversity of behavior willprovide for more confidence that the assessment will be protective of exposure conditions at themanagement site. Effort should also be made to ensure that the species used in such tests are sensitiveto contaminants, i.e., they respond to the presence of contaminants. Taxa vary in their sensitivity tocontaminants with respect to one another and among contaminants. Even though limited understandingof this variation in sensitivity currently prevents tailoring assessments for specific mixtures ofcontaminants or benthic communities at disposal sites; it must be acknowledged that using multiple testswith different species is a precautionary approach for assessing sediments (Cairns 1986).Water-column Toxicity Tests: Sediments will be suspended within the water column during dredgingand dredged material disposal operations. In some cases assessment questions regarding the potentialfor effects on organisms within the water column will be posed. In such cases, water column toxicity testsmay be used to address the concern. These tests generally make use of planktonic species includingalgae, copepods, and other arthropods (e.g., cladocerans), as well as larval molluscs, echinoderms, andfish (Figure 12). These tests, described in detail in USEPA/USACE (1998), are commonly conductedusing a dilution series of sediment-water mixtures (e.g., elutriates) or water extracts of sediment that areintended to represent the range of water-sediment mixtures organisms would be exposed to in the field.26

Americamysis bahiaDaphnia magnaPimephales promelasFigure 12.Marine (Americamysis) and freshwater (Daphnia and Pimephales) testspecies commonly used in water-column toxicity testsBioaccumulation Tests: Addressing questions concerning the potential for contaminants in dredgedmaterials to move into the food chain and produce effects in organisms above and beyond the borders ofa disposal site begins with assessing bioaccumulation potential. Bioaccumulation, in this case, refers tothe movement of contaminants from the sediment matrix into the tissues of exposed organisms. It isimportant to recognize that bioaccumulation tests provide a measurement of exposure rather than effect.Bioaccumulation of a compound will not always result in an adverse effect on the organism accumulatingthe compound. In the case of essential nutrients (e.g., zinc and copper), a certain amount ofaccumulation is required to support normal physiological function. In general, adverse effects from anycontaminant will only be manifest after the concentration exceeds a specific tolerance level ortoxicological threshold. For this reason careful attention must be given to interpreting bioaccumulationdata. Organisms commonly used in bioaccumulation testing are shown in Figure 13.Laboratory bioaccumulation tests are generally conducted by exposing infaunal organisms to beddedsediments under controlled conditions and recovering the animals at the end of the exposure to measurethe concentration of contaminants of concern in the tissues of the test organisms. Test organisms used inbioaccumulation tests are generally selected on the basis of their relative tolerance to contaminants (i.e.,they survive the exposure) and their body size, such that there is sufficient tissue recovered at the end ofthe exposure for chemical analysis.Because of the expense and time involved in conducting bioaccumulation tests, alternative approacheshave been developed for assessing bioaccumulation potential. One of these approaches is calledThermodynamic Bioaccumulation Potential (TBP). This approach makes use of the principle ofequilibrium partitioning of nonpolar organic chemicals as a means of estimating the amount of chemicalthat will partition to the lipid phase within the organism from the organic carbon phase of the sediment atequilibrium. The TBP can thus be calculated as27

Neanthes arenaceodentataMacoma nastulaLumbriculus variegatusNereis virensFigure 13.Marine species commonly used in bioaccumulation testsTBP = BSAF ( Cs foc)flwhere:TBP = whole body wet-weight concentration of the contaminant in the same units as C sBSAF = biota sediment accumulation factorC s = concentration of the nonpolar organic chemical in the whole sediment on a dry weight basisf oc = total organic carbon content of the sediment expressed as a decimal fraction (i.e., 3 percentequals 0.03)f l = percent lipid content of the organism expressed as a decimal fraction of whole-body wetweight (i.e., 3 percent equals 0.03)The BSAF is an empirically derived coefficient that can be calculated from previous laboratorybioaccumulation tests or using data from field-collected organisms where one has data on the steadystateconcentration of the specific contaminant of concern in the tissue of the organism, contaminantconcentration in the sediment, percent lipid content of the organism, and percent organic carbon contentof the sediment. With these data the BSAF can be calculated aswhere:CbflBSAF =C fsoc28

Cb = Steady-state contaminant concentration in wet tissueAs with all the tools discussed within this document, assumptions are associated with the use of thisapproach for estimating bioaccumulation potential from chemical data, but evidence collected to dateindicates that this approach can provide reliable estimates of bioaccumulation potential, conditioned uponthe quality of the input data (Clarke and McFarland 2002). The U.S. Army Corps of Engineers (USACE)has developed a database of published BSAFs and lipid data that can be accessed athttp://el.erdc.usace.army.mil/bsaf/bsaf.html. Approaches are also being developed to combine tissuebasedtoxicity data with bioaccumulation test results to make statements about the potential for adverseimpacts through this pathway. USACE has also published the Environmental Residue-Effects Database(ERED), which summarizes published information where effects (i.e., toxicity) have been associated withspecific concentrations of contaminants in tissue. This database can be accessed athttp://el.erdc.usace.army.mil/ered/index.html.Test Exposure Periods and EndpointsExposure Duration: Tests measuring effect (i.e., toxicity tests) can be conducted using short or longexposure periods. Toxicity tests measuring effects during relatively short exposures, with respect to thelife cycle of the test organism, are referred to as acute tests. Acute tests that have been applied toevaluate dredged material have included exposure periods as short as a few hours to days. Tests usinglonger exposures that include significant portions of an organism’s life cycle are called chronic tests.Current examples of chronic tests that have been applied to evaluate dredged material involve weeks(e.g., 3-4) of exposure. The decision to select an acute versus a chronic test during an evaluationdepends on the specific assessment questions the test is intended to address. Care should be taken tomatch the exposure conditions in the test to the exposure conditions that are expected at the site ofconcern, within the limits of what is logistically feasible. For example, water column exposures at anopen-water management site during disposal operations are generally short, on the order of a few hours.Should questions arise concerning the potential for water-column impacts during such operations, acutewater-column toxicity tests conducted over a period of several hours would likely provide the mostrelevant and meaningful information about the potential for impacts. When exposures are expected to belonger, as in the case of deposited sediments at a management site, longer-term acute and chronic testswill likely provide more meaningful information regarding the potential for impacts.With regard to bioaccumulation tests, length of exposure will affect how much contaminant accumulateswithin the tissues of the exposed organism. For organic contaminants, accumulation within the tissues oforganisms generally follows an asymptotic curve where concentration in tissue increases with exposuretime until a steady state is achieved between the rate of accumulation and elimination. Time to steadystate is influenced by a number of factors including the chemical/physical properties of the contaminant(e.g., log k ow ), the biological attributes of the organism (e.g., percent lipid content), and the geochemicalcharacteristics of the sediment (e.g., organic carbon content). The situation is more complex and lessunderstood for metals. For these and other logistical reasons, bioaccumulation tests are typically run for aminimum of 28 days. When desired or necessary, experimental and mathematical approaches can beapplied to estimate steady-state concentrations of most contaminants of concern (see USEPA/USACE(1998)).Endpoints: A large number of biological responses in test organisms have been used as endpoints fortoxicity tests. The most commonly used endpoint for tests applied to dredged material is survival (orconversely, mortality). Survival is measured by calculating the difference between the number of testorganisms added to an individual test chamber (replicate) at the beginning of the test and the number oftest organisms recovered from the test chamber at the conclusion of the exposure period. Sublethalendpoints can also be measured, including behavioral responses, individual growth (change in weightover the exposure period), reproductive output (number of offspring produced), and more subtlephysiological or biochemical responses. Judgments about the biological and ecological relevance of theendpoints measured in a toxicity test must be made before considering the use of those data to makedecisions about whether a dredged material requires special management. Whereas understanding and29

communicating the adverse nature of mortality during a toxicity test presents relatively few problems,relating the biological/ecological importance of more subtle responses in growth, reproduction, orchanges in expression levels for specific proteins or enzymes in the case of molecular biomarkerspresents challenges. There is broad consensus that effects measured in individual test organisms thathave a strong biological relationship to adverse impacts on the viability of populations (i.e., effects onsurvival, growth, reproduction) should carry more weight in decision making than effects with a moretenuous or ill-defined relationship to population viability (e.g., molecular responses).HistopathologyHistopathology involves the identification of abnormalities in the tissues of organisms. Abnormalities,such as lesions, can be related to exposure to anthropogenic contaminants as well as other agents. Suchmeasures of effect have been used to evaluate hazards posed by sediment-associated contaminants(e.g. DelValls et al. (1998)). Histological endpoints can be measured as part of a laboratory toxicity test(usually a chronic test) or as part of a field study where field-collected animals are assessed. In both ofthese cases it is a measure of effect; however, conclusively identifying the specific agent(s) causinghistological effects is generally beyond the reach of current science. Appropriate use of histologicalendpoints is highly dependent on careful selection of both the test organisms (e.g., clams, fish, etc.) andtissues (e.g., gills, liver, digestive, gonad, brain) to be assessed and the training of personnel responsiblefor identifying and quantifying histological effects. Technological advances made in recent years and theadoption of approaches for ensuring data quality have increased the opportunities for using histologicalapproaches as a more routine component of environmental assessments.Biomarkers of Effect and ExposureThe term biomarker refers to the use of molecular responses in living systems to provide informationabout contaminant exposure and effect. Organisms will respond at the molecular level whencontaminants interact with the genetic material within the organism’s cells. Genotoxicology is the study ofthis interaction and the effects resulting from it. Such effects can include mutations in the genetic materialitself (mutagenicity), developmental abnormalities (teratogenicity), and cancer formation (carcinogenicity).Over the last several years, a number of tests have been developed for measuring exposure and effectsusing genotoxicological endpoints. These tests can be divided into three categories of biomarker tests: 1)integrators of genotoxic effects, 2) indicators of genotoxicity, and 3) biomarkers of exposure (Inouye1999). A test in which a whole organism (e.g., a fish) is exposed to a suspect material, and tumor orcancer formation rates in the test organism are measured as test endpoints, would be an example of anintegrator of genotoxic effects. Due to the length of time necessary to conduct such tests (e.g., months),these tests are unlikely to be widely applicable for dredged material evaluations. Tests which serve asindicators of genotoxicity most commonly make use of bacteria or cultured eukaryotic cells to measuredamage to DNA (e.g., strand breaks) or chromosomal aberrations. These tests generally provide for morerapid screening of samples, but they typically require testing with chemical extracts of sediment ratherthan intact whole sediment. Because tests using chemical extracts of sediment provide no informationregarding the bioavailability of contaminants producing a response, these approaches have limited utilityas regulatory assessment tools. Tests that are used as biomarkers of exposure generally involveexposures of whole organisms to whole sediment where evidence that the organism has been exposed tocontaminants is based on such endpoints as the presence of chemical metabolites in the organism’s bile,the presence of DNA adducts, or changes in enzyme levels within the organism. Because these endpointconditions within the organism will not necessarily lead to adverse biological effects (e.g., tumorformation), these tests are used to assess exposure rather than to make definitive judgments about thepotential for effects. As research in this area of biological testing continues (Section H), these tests willlikely become a more commonly applied tool in dredged material evaluations.30

E. Developing Biological Tests for Regulatory UseBiological tests for assessing sediment quality have been widely used to manage dredged material. In allsuccessful regulatory applications of biological tests, the tests themselves were developed throughsignificant research and development. The research investment required is justified on the basis of thecost implications of the regulatory decisions involved and the uncertainties associated with all analyticaltools used in the evaluative process, including biological tests. A question that must be asked during theresearch effort to develop a biological test is “When is the test ready for regulatory use?” Assessmenttools undergo a maturation process as knowledge and experience are gained regarding theirperformance and reliability under the variable conditions involved in their application. In general, onewould expect that investments in research and development made in a biological test should returnbenefits in terms of reduced uncertainty associated with its application and increased reliability in itsperformance as a predictive tool for decision-making.Who Develops Biological Tests?A broad range of public and private sector organizations develop biological tests. Government agenciesthat utilize such tests for their regulatory programs have sponsored development of biological tests,including the U.S. Environmental Protection Agency (www.epa.gov/OST), The U.S. Army Corps ofEngineers (http://el.erdc.usace.army.mil/dots/doer/doer.html), Environment Canada (www.ec.gc.ca),RIKZ in The Netherlands (www.zeeslib.nl), and others. In other cases, biological tests have beendeveloped through academic research programs or through private sector initiative. The original sourcefor a particular biological test is a matter of little importance in judging the value of the test for a particularapplication. Judging the suitability of a particular test for an application should be based on the qualityand quantity of scientific information available regarding the test itself and its application with fieldcollectedsediments.A Framework for Guiding Test DevelopmentDillon (1994) proposed a framework for guiding the development of biological tests intended for use inregulatory evaluations of dredged material. This framework is composed of a progression of developmentor maturation phases for biological tests beginning with 1) initial scoping, research and development bythe test proponent, 2) expansion of development and application by multiple laboratories, 3) developmentof a standard test method, and 4) evaluation by user groups. Key components of these phases will bediscussed in brief below.• Rationale for the test and its endpoints: One of the first steps in developing or adapting abiological test for use in evaluating dredged material is to define the rationale for using the test indecision-making, i.e., describing how the test, and the data it produces, would contribute to answeringquestions about the likelihood for a particular sediment to produce adverse effects of regulatoryrelevance. This rationale should include an appreciation for the regulatory and evaluative frameworkbeing contemplated and where the test would fit within that context. How a test will be used will certainlybe related to the endpoints that are selected for measurement during the test, e.g., effects on survival,growth, reproduction, or some other life history characteristic. The test endpoints that will be measuredmust be related in a logical fashion to a biological or ecological receptor, effect, or process of concern.• Selection of test organism: Designing a biological test necessitates selecting a test organism touse in the test. Making a proper match between the objectives for a specific test design and the testorganism to be used requires considerable knowledge about the subject organism. Some of theinformation that must be collected and understood concerns 1) the ecology of the organism and itsrelevance to the dredging or disposal sites of concern, 2) how the organism interacts with the media to betested, 3) the nature of the organism’s life cycle, including its growth and reproductive patterns, 4) theorganism’s tolerance for a range of environmental variables, e.g., salinity, temperature, etc. Of particularimportance in regard to interpreting test results, an understanding must be developed for the testorganism’s sensitivity to a range of contaminants of concern and to potential confounding factors like the31

grain size distribution of the sediment (DeWitt et al. 1988) and naturally occurring substances likeammonia and hydrogen sulfide (Sims and Moore 1995a, 1995b). Information concerning the availability oftest organisms in nature or their capacity for being handled or cultured in a laboratory setting will help insetting logistical constraints for a particular test.• Experimental and Statistical Design: For a test to be successfully applied in a regulatory programit must be designed to meet a specific objective of relevance to the program, and that design must beconsistently applied. The experimental conditions under which the test is performed will be defined (e.g.,temperature and light regime, food ration, etc.) and the influence of these conditions on the performanceof the test organism and the test as a whole must be understood. Performance standards are to bedeveloped to ensure that the organisms being used in the test are of sound health and that the test wasconducted properly. In addition to these experimental features, the statistical elements of design must bedefined. Such elements would include defining the hypotheses to be tested, setting the magnitude ofresponse to be detected by considering statistical power, replication, and inter-laboratory precision. Theprocess for optimizing the design of a biological test will also consider the costs that will ultimately berequired to use the test. Where possible, protocols should be designed to minimize the costs associatedwith using the test.• Test ruggedness: The “ruggedness” of a test refers to the “insensitivity of a test method todepartures from specified test or environmental conditions” (ASTM 1992). Such conditions will includedesign features of the test (e.g., how organisms are fed during the test) and conditions determined by thematerial being tested (e.g., grain size distribution). The consequences for some departures from specifiedconditions will be determined, in part, by well-developed Quality Assurance/Quality Control guidance. Forexample, the necessity for invalidating the results of a biological test if the temperature in the testchambers was not maintained at the level specified in the protocol will be based on the magnitude ofdeparture and knowledge of the sensitivity of the experimental system to temperature. In general, thedegree to which the performance of a test can be influenced by such departures will have implications forthe overall reliability of the test and the costs associated with using the test in a regulatory program. Testsystems that are very sensitive to small departures from specified conditions will result in higher costsbecause of the need to “re-test” sediments when results are invalidated.• Testing with dredged material: Before applying the test to make regulatory decisions, the testshould be transitioned out of a pure research phase by evaluating the performance of the test with abroad range of “real world” dredged materials. This step in the development process will providedecision-makers with a measure of confidence that the test will provide meaningful and reliableinformation upon which to base management decisions when it is implemented within a regulatoryprogram.• Inter-laboratory studies: Under most application scenarios, a biological test will be conducted bydifferent people within the same testing laboratory and by different testing laboratories. To gage thedegree of variation in results introduced by these conditions, an inter-laboratory testing study can beundertaken to assess the precision associated with a specific test. In such a study, multiple testinglaboratories perform the same test on the same sediments and the results achieved by the laboratoriesare compared. This information provides users and decision-makers with a measure of confidence in theconsistency of test performance and application. The variations in test results that are introduced whenconducting biological effect measurements at different laboratories can be gaged in an inter-laboratory orround-robin comparison study (e.g. Burton et al. 1996; Mearns et al. 1986; Schlekat et al. 1995; Williamset al. 1986).• Interpretive guidance: The information provided by a biological test is only meaningful if it can berelated in some fashion to issues of regulatory concern. Interpretive guidance is information, in the formof guidance, that relates the responses in a specific biological test to assessment endpoints of biological,ecological, or regulatory significance. Such guidance is intended to address the question “How is thebiological response measured during the test related to the potential for impacts of concern at my site?”32

Interpretive guidance must be developed to provide meaning and weight to decisions based on theresults of biological tests.• Transition to multiple users and subjection to peer review: One measure of the utility of a test andits acceptance within the scientific community is the extent to which a specific test is used by individuals,laboratories, or organizations other than the test’s principle proponent. A test that is used by multiple,independent groups will have attained a degree of maturity through use and critical inspection. This willbe most evident in the degree to which a test has been subjected to peer review through publication inthe open, scientific literature.• Verification and validation: During the development phase of a biological test, data will becollected that can be used to verify, under a range of sediment conditions, that the test responds in alogical and predictable fashion to contaminated sediments. This verification step is in large measure anatural consequence of the research and development effort. Validating that the test has predictive valuewith respect to impacts at a field site is a more challenging question to address. There are a fewexamples of validation efforts where biological test data were compared to impacts at field sites (Moore2001; Swartz et al. 1986; McGee et al. 1999); however, few such efforts have been conducted at dredgedmaterial disposal sites (Peddicord 1988), in part because of the scales and costs involved in such efforts.Other ways to assess the predictive quality of a new biological test might include assessing the degree ofconcordance among similar biological tests of the same sediment treatments (i.e., a comparison amongtests) or smaller-scale efforts at validating field responses that make use of mesocosms.• Developing a standard method and instructional materials: As the methods used to conduct abiological test become formalized, a standard approach/method must be developed to ensure that thetest can be consistently and reliably applied. Standard-setting elements of government agencies such asthe United States Environmental Protection Agency, Environment Canada, or the European Union havedeveloped formalized, detailed, standard method guides for programs under their jurisdiction. Nongovernmentalgroups such as the American Society for Testing and Materials also develop standardizedmethods through a peer-review process. Training, instructional materials and workshops may be requiredto transition the test to the parties who are expected to use and conduct the test.• Evaluation by user groups: Successful transition of a biological test from research anddevelopment to the user community should include establishing a mechanism through which users canprovide feedback on the performance of the test. As experience is gained with a particular test, questionsand/or problems may arise that can be solved by making changes to the test method. Providing amechanism for those in research and development to interact with users will ensure that solutions to anyproblems that arise can be implemented in an efficient and timely manner.When is a Biological Test Ready to Use in Decision-Making?Answering this question depends on a number of factors, including the degree of significance orimportance associated with the management decision at issue. If biological tests will be used to makedecisions involving considerable cost, then it’s reasonable to require that the tests used have a record ofpositive experience gained through research and development and/or field application. Undercircumstances where management decisions may be less costly, e.g., non-regulatory monitoring efforts,the use of biological tests with less maturity may present less of a problem. In fact, such applications ofnew protocols or methods provide opportunity for decision makers to evaluate and gain experience usingnew biological tests.33

F. Quality Assurance/Quality ControlBefore biological test data are used to make sediment management decisions, conclusions must bereached regarding the quality of the data. Data quality is assessed to establish confidence that anyobserved responses can be attributed to the presence of contaminants in the sediment or at the site inquestion. These conclusions are reached by addressing such questions as:• Were the samples that underwent testing collected, handled, and stored according to definedstandard operating procedures (SOP)?• Were the biological tests conducted in a manner consistent with the SOP for the tests?• Were the performance criteria for the tests met?• Were there any deviations from water quality targets during the course of the tests?• Has the accuracy of data transcription and analysis been confirmed?• Can any potential influence of modifying or confounding factors be accounted for?A Quality Assurance and Quality Control (QA/QC) program provides a process during data collection andprocessing to ensure that the subject data are sufficient, appropriate, and of a known and documentedquality (Moore et al. 1994, USEPA/USACE 1998). A QA/QC program for biological effect measurementsshould be composed of a number of elements that will be described in the following sections.Establishing Data Quality Objectives: The data quality objectives process provides a structure forreaching decisions about what and how data are to be collected (USEPA 2000a). Before collecting data,one must know why the data are being collected and how those data will be used to reach a decision.The data quality objectives process developed by the USEPA is composed of the following seven steps:• Develop a statement of the problem.• Identify the decision(s) to be made.• Identify the inputs required to make the decision(s).• Define the boundaries (e.g., spatial and temporal) of the study.• Develop decision rules.• Specify tolerable limits for decision errors.• Optimize the design for collecting the data.Within the context of biological testing, decision rules, established in advance of data collection, woulddefine the numerical thresholds and logic that will be used to reach specific conclusions about thematerial being tested. For example, in the U.S. dredging program, sediments evaluated with 10-d toxicitytests using marine and estuarine amphipods are generally not considered toxic until mortality observed indredged material is statistically different and 20 percentage points greater than mortality observed in areference sediment. Decision rules, based on technical and policy considerations, will vary among testsas well as among the programs, agencies, and jurisdictions conducting the evaluations. Reachingdecisions about tolerable limits of decision error involve considering statistical power and error rates. Inthe example concerning amphipod testing in the United States, statistical significance is defined as beingachieved using an alpha level (α) equal to 0.05, which specifies the level of type 1 error associated withthe statistical test (see Section H for further discussion). At the conclusion of the data quality objectivesprocess, users will have designed a detailed sampling and analysis plan that describes how manysamples are to be collected, where they are to be collected, how the samples will be handled andprocessed, and how the data will be analyzed for use in decision making. When these steps arecompleted in advance of data collection, they help to ensure that the data collection and analysis processis conducted in a cost-efficient and timely manner.Ensuring Sample Integrity: Steps must be taken during the evaluation process to ensure that thesediment or water samples to be tested are representative of the conditions at the site of concern (e.g.,the proposed dredging or disposal site). This will involve documenting sample locations and conditions atthe site of collection, following proper chain of custody procedures for the sampling, and storing the34

samples in a manner that minimizes the likelihood that sample condition will change. Care should betaken to prevent the introduction of contaminants from the sampling equipment or the laboratory wherethe testing will occur. Maintaining low temperature (4-6 °C) is generally recommended (USEPA 2001)during shipping and storage to minimize changes in geochemistry. Freezing of sediments is generally notrecommended for samples that will undergo biological testing because this could lead to changes in thebioavailability of any sediment-associated contaminants present. In general, biological tests should beperformed as soon as possible after sampling. However, storage periods of 1 to 2 months are generallyconsidered acceptable (e.g., USEPA/USACE 1998). Achieving these storage limits requires good projectplanning.Use of Standard Operating Procedures: Standard Operating Procedures (SOPs) are detaileddescriptions of all actions and equipment used to accomplish a specific task. To ensure that samples ofdredged material are collected and tested in a known and consistent manner, SOPs must be developedor identified before an evaluation and followed during an evaluation. A SOP for a biological test willinclude details on (1) procedures to be followed in evaluating the condition of the test organisms to beused, (2) the laboratory conditions to be maintained during the conduct of a test, and (3) measurementsto be taken to evaluate whether factors other than contaminants (i.e., so called modifying factors) couldinfluence the results of the test. Care must be taken to follow SOPs, while documenting any deviationsfrom the SOPs, in order to establish confidence that any observed effects are due to contaminants.Over the last several years, a number of protocols for biological tests of media relevant to dredgedmaterial evaluation have been published that could serve as the basis for SOPs that would beimplemented by individual testing laboratories (Tables 3 and 4). These protocols have been developedby, among others, the America Society for Testing and Materials (ASTM), the U.S. EnvironmentalProtection Agency (USEPA), the U.S. Army Corps of Engineers (USACE), Environment Canada (EC),and the Dutch National Institute for Coastal and Marine Management (RIKZ). Prior to testing, agreementshould be reached among relevant stakeholders and regulatory agencies about which biological testsand SOP will be used in a dredged material evaluation.35

Table 3Freshwater Sediment BioassaysMatrix Taxa EndpointGeneralWholeSedimentWaterColumnIn situFish, amphibians,macoinvetebratesExposureTimeStandard Operating ProcedureVarious Various APHA 1999; ASTM, E1604-94 (ASTM 2002b);USEPA/USACE, 823-B-98-004 (USEPA/USACE 1998)General Various Various ASTM, E1525-02 (ASTM 2002a)AmphibiansSurvival, growth 96-h ASTM, E1439-98 (ASTM 1998c)behavior, deformityMacroinvertebratesSurvivalGrowth10-d ASTM E1706-00 (ASTM 2000a); EC, EPS 1/RM/32,EPS 1/RM/33 (EC 1998a); EC, EPS 1/RM/33 (EC1998b); EPA/600/R-99/064 (USEPA 2000b)Macroinvertebrates Bioaccumulation 28-d ASTM E1688-00a (ASTM 2000c); EPA/600/R-99/064(USEPA 2000b)EmergentMacrophytesAmphibiansFishGrowth 2 – 6 wks ASTM; E1841-96 (ASTM 1996)Survival, growthbehavior, deformity96-h ASTM, E1192-97 (ASTM 2003b); ASTM, E1439-98(ASTM 1998c)Survival, behavior 96-h ASTM, E1192-97 (ASTM 2003b); EC, EPS 1/RM/9 (EC1990a); EC, EPS 1/RM/10 (EC 1990b); EPA-821-R-02-012 (USEPA 2002a); ISO 7346-1:1998 (ISO 1998a);ISO 7346-2:1998 (ISO 1998b); ISO 7346-3:1998 (ISO1998b)Life cycle, survival,growthLocomotion,Feeding, Behavior7 – 120-d ASTM, E1241-98 (ASTM 1998b); EC, EPS 1/RM/22(EC 1992b); EC, EPS 1/RM/28 (EC 1992d); EPA-821-R-02-013 (USEPA 2002b); ISO 10229:1994 (ISO1994); ISO 12890:1999 (ISO 1999a)Various ASTM, E1711-95e1 (ASTM 2003d)Macroinvertebrates Survival, behavior 48-h ASTM (1997); EC, EPS 1/RM/11 (EC 1990c); EC, EPS1/RM/21 (EC 1992a); EPA-821-R-02-012 (USEPA2002a)CladocernsSurvival, growth,reproduction7-21-dASTM E1193-97 (ASTM 1997a); EPA-821-R-02-013(USEPA 2002b); ISO 10706:2000 (ISO 2000)Mobility Acute ISO 6341:1996 (ISO 1996)Algae Growth 96-h ASTM, E1218-97a (ASTM 1997b); EC, 1/RM/25 (EC1992c); EPA-821-R-02-013 (USEPA 2002b); ISO8692:1989 (ISO 1989)Aquatic Macrophyte Growth 14-d ASTM, E1913-97 (ASTM 1997c)Macroinvertebrates Survival, Growth Variable ASTM WK423 (ASTM 2003e)FishBivalve Survival, Growth Variable ASTM E2122-01 (ASTM 2001)Suspension Bacteria Bioluminescence 20-min. EC, EPS 1/RM/21 (EC 1992a); RIKZ (1999)Pore water Rotifer Survival 24-h APHA (1999); ASTM, E1440-91 (ASTM 1998d)Algae Growth 3-d APHA (1999)Elutriate Various Various Various USEPA (1991), USEPA/USACE (1998)36

Table 4Marine Sediment BioassaysMatrix Taxon EndpointGeneralWholeSedimentWaterColumnFish, amphibians,invertebratesExposureTimeStandard Operating ProcedureBehavior Various APHA (1999); ASTM, E1604-94 (ASTM 2002b);USEPA/USACE, 823-B-98-004 (USEPA/USACE 1998)General Various Various ASTM, E1525-02 (ASTM 2002a); EC, EPS 1/RM/40E (EC2001b)Invertebrates Bioaccumulation 28-d ASTM E1688-00a (2000c)Amphipod Survival Growth 10-d, 28-d ASTM E1367-99 (ASTM 1999); EC, EPS 1/RM/26 (EC2998d); EC, EPS 1/RM/35 (EC 1998d); EPA/600/R-94/025 (USEPA 1994); EPA/600/R-01/020 (USEPA2001); RIKZ (1999); RIKZ (2000a); Roddie & Thain (2001)Echinoderm Survival 14-d EC, 1/RM/27 (EC 0000); RIKZ (2000c)Bacteria Bioluminescence 20 min RIKZ (2000b)PolycheateSurvival, GrowthBioaccumulation10, 20, 28-d ASTM, E1611-00 (ASTM 2000b); EC (1998); Thain &Bifield (2002); EC, EPS 1/RM/41E (EC 2001a)Bivalve Embryo devel. 2-d ASTM, E 724-98 (ASTM 1998a)Mysid ShrimpKelpSurvival, growth,reproductionGermination,GrowthFull lifecycleASTM, E 1191-03a (ASTM 2003a); ASTM, E1463-92(ASTM 1998e); Chapman et al. (1995)48-h Chapman et al. (1995)Mollusc Devel. 48-h Chapman et al. (1995)EchinodermSurvival, Devel.,Fertilization72-h, 20-minChapman et al. (1995)Bivalve Survival, Devel. 48-h Chapman et al. (1995)FishSurvival, behavior 96-h ASTM (1997); EPA 821-R-02-012 (USEPA 2002a)Life cycle, surival, 7–120-d ASTM, E1241-98 (ASTM 1998b); Chapman et al. (1995)growthInvertebrates Survival, behavior 48-h ASTM (1997); EPA 821-R-02-012 (USEPA 2002a)Amphibians Survival, behavior 96-h ASTM (1997)Algae Growth 96-h APHA (1999); ASTM, E1218-97a (ASTM 1997b); ISO10253:1995 (ISO 1995)Seaweed Reproduction 2-d ASTM, E1498-92 (ASTM 1998f)PolychaetousAnnelidsFishSurvival,reproductionMobility, Feeding,Behavior96-h, 10,14, 21, 28-dASTM, E1562-00 ASTM 2000a)Various ASTM, E1711-95e1 (ASTM 2003d)In situ Bivalve Survival, growth Variable ASTM E2122-01 (ASTM 2001)Suspension Bacteria Bioluminescence 20 min APHA (1999); EC, EPS 1/RM/21 (EC 1992a); RIKZ(1999); ISO 11348-1:1998 (ISO 1998d); ISO 11348-2:1998 (ISO 1998c); ISO 11348-3:1998 (ISO 1998f)Pore water Dinoflagellates Bioluminescence 7-d, 4-h ASTM, E1924-97 (ASTM 1997d)ElutriateExtractRotifer Survival 2 -d APHA (1999); ASTM, E1440-91 (ASTM 1998d)AlgaeGermination, 4 -d Hooten and Carr (1998)GrowthEchinodermFertilization,Embryo devel.2-d ASTM, E1563-98 (ASTM 1998g)Bivalve Embryo devel. 2-d Thain (1991) ; ASTM E724-98 (ASTM 1998a)Copepod Survival, devel. 4-d ISO 14669:1999 (ISO 1999b)EchinodermRat hepatoma celllineSurvival,DevelopmentDioxin-like mode ofaction2-d USEPA (1990)1-d RIKZ (2000d)37

Taxonomic Verification of Test Species Identity: Species differ in the general characteristics of theirbiology and their sensitivity to contaminants. For these reasons, actions must be taken to ensure that thespecies called for in the protocol is the one being used in the biological test. This requires that personnelperforming the biological tests have sufficient knowledge of the test organism and related and/or cooccurringspecies to confirm that the correct species is being used in the test. In some cases, outsideexperts may be required to perform these identifications. For testing involving cultured animals, periodicconfirmation of species identification will not be required as frequently as when using test organisms thatmust be collected from the field, where some degree of confirmation is required for each test performed.Test Organism Condition: Observations are made during a biological test to determine whether the testorganisms are responding to test conditions in a manner consistent with their past performance. Theseobservations are made by using positive and negative controls. A positive control is intended to identifyand exclude pools of test organisms that are behaving or responding in an abnormal manner (e.g., due topoor health). The positive control test is conducted by exposing a subset of the pool of test organisms toa known contaminant or mixture of contaminants. These tests are most commonly conducted as shortterm,water-only exposures to a dilution series of a known single contaminant; however, spikedsediments could also be used as positive controls. The response of the organisms (e.g., 96 hour LC50,Figure 14) is compared to historical positive control data displayed in the form of a control chart, like theone shown in Figure 15. The species-specific control charts generated by the testing laboratory are usedto gage whether the test organisms show signs of significant, unusual contaminant tolerance orsensitivity. A negative control generally takes the form of an additional treatment (a sediment that the testorganisms are known to perform well in) that is tested alongside the dredged materials being evaluated.The negative control sediment is commonly the sediment the organisms are collected from in the field orcultured upon in the laboratory. The negative control sediment should be relatively free of contaminantsand produce consistent and high rates of survival, growth, and reproduction in the test organism. Theprincipal purpose of the negative control is to check whether experimental conditions were maintained atlevels specified by the SOP and that are conducive to the health and performance of the test organism.Performance criteria are established within the test protocol for each test endpoint (e.g., organismsurvival, growth etc.) to gage whether animals in negative control sediment are performing as required(e.g., Table 5). Failure to meet the negative performance control standard criteria can justify the need torepeat the biological test.38

Survival (%)10050LC 50 = 12 ppm00 5 10 15 20Concentration (ppm)Figure 14.Lethal concentration causing 50-percent mortality (LC 50 ). In this case, theLC 50 would be ~12 ppmControl chart Corophium volutatorLC50 72h NH4 2+ [mg/l24020016012080400Feb-99 May-99 Aug-99 Dec-99 Mar-00 Jun-00 Oct-00 Jan-01dateLab.1Lab.2TAC low erTAC upperFigure 15.Control chart showing the past performance of Corophium volutatorexposed to ammonium chloride for 72-h at a laboratory. Observations abovethe upper line or below the lower line indicate poor quality of the testorganisms (too insensitive or too sensitive, respectively). TAC – TestAcceptability Criterion39

Table 5Test Acceptability Criteria and Modifying Factor Criteria for the 10-d Amphipod Bioassay withCorophium volutator as Used in the Assessment of Contaminated Dredged Material fromHarbours Along the Coast of the Netherlands (Stronkhorst et al. 2003)Test acceptability Criterion UnitStorage time of the sediment ≤ 4 weeksOverlaying water-Temperature 15 ± 1 °C-Oxygen saturation > 50 %Sensitivity of the test organisms:-positive control: LC50 for ammonium chloride 36 – 220 mg NH 4 Cl/l-negative control: survival in clean sediment > 90 % survivalModifying factors Criterion Unit-fine sediment fraction < 63 µm < 90 % dry wt sediment-salinity in overlaying water 4 – 40 %-pH of overlaying water 7.0 – 9.0 SU-total ammonia of overlaying water-at pH 7.0 192 mg/l-at pH 7.5 106 mg/l-at pH 8.0 60 mg/l-at pH 8.5 31 mg/l-at pH 9.0 10 mg/lTest Performance Conditions: Test organisms will respond to changes in environmental conditionsduring the test. An SOP therefore specifies criteria for laboratory conditions to ensure that tests areconducted in a manner that minimizes the influence of adverse environmental conditions. Table 5provides a generic example of acceptability criteria for an amphipod toxicity test. Temperature, pH,salinity, water hardness, and the oxygen levels in the overlying water are among the most commonvariables that are monitored during toxicity testing of dredged material to assure that any observed testorganism responses are caused by contaminants rather than unfavorable test conditions.Modifying Factors: Test organisms can respond to a range of natural sediment features that areunrelated to the presence of contaminants. For this reason, care must be taken to ensure that responsesobserved in a toxicity test can be attributed to the presence of contaminants of concern rather than socalledmodifying or confounding factors, such as the grain size distribution of the sediment or thepresence of un-ionized ammonia or sulfides. Developing an understanding of these tolerance limits fortest species is an important element in toxicity test development. When potential modifying factors in asediment test are within the tolerance limits of the test species, one can conclude that any observedresponses in the bioassays are not due to modifying factors, and vice versa. Table 5 provides exampletolerance limits for modifying factors in an amphipod toxicity test. Sediments should be characterized withrespect to potential modifying factors prior to biological testing to (1) guide the selection of the toxicitytests to be used in order to avoid the potential influence of such factors, (2) determine the need to addadditional controls to the experimental design to account for the influence of such factors (e.g., use of agrain size control), or (3) make adjustments to the sediment prior to testing. For example, high ammonialevels in sediments can be reduced by various methods (USEPA 1994, Ferretti et al. 2000) prior to testingto eliminate the influence of this compound on organism response. However, when manipulatingsediments to reduce the influence of modifying factors, care must be taken to avoid altering, in anysignificant fashion, contaminant concentration or bioavailability. Changes in pH and salinity may modifythe bioavailability and toxicity of some contaminants, i.e., metals (Riba et al. 2004b).40

Sound Data Management Procedures: During the conduct of a biological test, data must be collectedand handled in manner that preserves their accuracy and quality. A test may meet all the performancestandards required by its protocol, but if the data are not managed in a manner that ensures theiraccuracy, the information produced by the test may not be appropriate for use in decision making.Validating or confirming the accuracy of transcription from laboratory notebook to computer database isbut one of several steps to ensure, in a manner that can be documented, that the data are credible.41

G. Interpreting the Results of Biological TestsAfter having passed the QA/QC review (Section F), the validated results of biological testing are used toanswer the assessment questions developed during the course of the evaluation. A range of perspectivesand approaches have emerged over the last 30 years for interpreting the results of biological tests todevelop inferences and reach conclusions about how dredged material should be managed. In somecases strict rules have been established for judging the relevance and meaning of the data. However, thisguidance recommends developing a more adaptable approach, based on using and integrating multipleLOE, that can more efficiently accommodate the variation and complexity inherent to assessingcontaminated sediments. The design and execution of sediment assessments will vary from project toproject due to differences in project goals, the environmental setting, and the specific set of contaminantsand receptors of concern for the project and site. Because of this variation, the means used to integratemultiple LOE to reach conclusions about how dredged material should be managed will vary dependingon the nature of the project and the information associated with the LOE.Developing Lines of EvidenceThe specific LOE that are developed to answer the assessment questions will depend on the selectedCOC, ROC, conceptual model, and questions of relevance to the assessment. An LOE is composed ofdistinct, but related, points of information. The term “line of evidence” is commonly used to refer tobroadly defined categories of information, e.g., sediment chemistry, toxicity test data, and benthiccommunity survey results. This document refers to six primary LOE as they relate to the fundamentalprocesses involved in describing the potential for risk, i.e., exposure and effects processes (as describedby Bridges et al. (2005)). These LOE are categorized according to the principal component of theecosystem where the exposures and effects occur (Figure 16). Receptors living in close association withbedded sediments can be adversely affected by sediment-associated contaminants through directcontact with those sediments, as in the case of benthic invertebrates, plants, and demersal fish.Receptors residing in the water, e.g., planktonic invertebrates and fish, can be exposed and affected bycontaminated sediments suspended in the water column or through flux of contaminants into thedissolved phase. Other receptors can be adversely affected by sediment-associated contaminants in amore indirect manner through the movement of contaminants within food chains, as would be the case forfish-eating birds and mammals, including humans. For each of the three ecosystem components inFigure 16 separate LOE are provided for exposure and effects information. This categorization of sixprincipal LOE captures all potential receptors that could be affected by contaminated sediments and thepathways through which they are exposed. The chief benefit of this categorization is that it establishes astrong linkage among the conceptual model, assessment questions, and the weight of evidence processused to reach conclusions about the nature, extent, and magnitude of risks.Once the specific LOE’s to be developed in the assessment are identified, specific measures of exposureand effect are selected. These measures describe the information that will be collected to makeinferences about exposure, effects, and ultimately, risk to ROC. For instance, in the case of assessmentquestions concerned with the status of the benthic community, measures of effect might include adescription of how sediment toxicity tests would be used to assess the potential for effects (e.g., whichtoxicity tests and endpoints would be used). In the case of assessment questions concerned with risks tofish-eating birds and mammals, relevant measures of exposure would include a description of how fishtissue concentrations will be estimated to assess exposure potential using bioaccumulation tests and/ormodeling. Answering assessment questions concerning risks to brown pelican will require assemblingpoints of information related to brown pelican exposure to contaminants and the potential for effects inthat receptor. The points of information assembled to characterize exposure and effects to brown pelicanwill differ significantly from the points of information used to characterize exposure and effects to thebenthic community. While sediment toxicity tests can provide useful information for characterizing thepotential for benthic effects, they are not directly relevant to characterizing effects to fish-eating birds. Inregards to zooplankton and fish that reside in the overlying water column, the potential for exposure andeffects during dredging operations can be measured using water column tests. Solid-phase bioassaysoffer little relevant information regarding the potential for effects in the water column. One of the reasonsfor this limitation is that the extent to which an organism is exposed to contaminants or suspended42

sediment in the water column will strongly depend on hydrodynamic conditions and the processinfluencing dilution at the disposal site. In the United States, for example, numerical models are used tocapture these processes and to develop inferences about the potential for adverse impacts to receptorsin the water column (USEPA/USACE 1998).Food Web(Indirect)ExposureEffectsWater Column(direct)ExposureEffectsWOEExposureEffectsSediment(direct)What is the nature, extent and magnitude of risk?Figure 16.Line of evidence relationships for a sediment assessment based on Bridgeset al. (2005)Which LOE’s are developed within an assessment, and which biological tests are used to generaterequired information, will vary from project to project, depending on the combination of contaminants andreceptors of concern included in the assessment. For example, a site with no bioaccumulative COCwould not include development of the food web LOE. Information concerning how multiple LOE’s areassembled and integrated to reach WOE-based conclusions about risks is the subject of guidance beingdeveloped by EnviCom Working Group 10.For many sediment assessments, multiple measures of exposure and effect would be selected and used.Choices about which and how many measures will be used in a given assessment will depend on thecharacteristics of the sites and the assessment questions and endpoints chosen. The approaches ortools that may be employed as measures of exposure and effect might include a combination oflaboratory tests or analyses, field measurements, and modeling efforts depending on the objectives andneeds of the assessment.43

Analyzing Test DataThe first and most straightforward step in interpreting biological testing data to develop LOE’s is tosubject the collected data to a statistical analysis. Guidance developed for the U.S. dredging program(USEPA/USACE 1998) provides detailed information on how statistical methods can be used to comparedata for test organisms exposed to dredged material. Detailed biological assessment method documentsfrom Canada, the United States, Europe, and others also provide this type of guidance (see Table 2).The most widely used approach to establish the significance of biological test results involves makingstatistical comparisons to a reference sediment. A reference sediment is a sediment that is largely free ofcontamination that is used to represent acceptable environmental conditions at the disposal site in theabsence of any previous disposal activity. The reference sediment is used as a type of standard forjudging the quality of the dredged material using the various responses measured in biological tests. Tominimize the potential influence of factors that could confound interpreting the comparison of results, thereference sediment should have geotechnical (e.g., grain size) and geochemical (e.g., percent organiccarbon) properties that are as similar as practicable to the dredged material being tested. In the mostwidely used reference sediment approach, a reference sediment is tested alongside the dredgedmaterials being evaluated, in addition to the control required by the SOP, during the conduct of thebiological test.The need for using a reference sediment is twofold: (1) control sediments, which are used to determinewhether the test was conducted in a manner consistent with the requirements of the SOP, may notadequately represent conditions at the disposal site, and (2) the variation inherent to measuring anyenvironmental quantity must be accounted for in the manner in which the data are used. It is important tonote that the ability of a bioassay to identify a statistical difference between a dredged material and areference sediment will depend on:1. The design of the bioassay. For instance, the larger the number of replicates of each sedimentincluded in the design, the greater the statistical power of the test, i.e. the greater the likelihoodthat a difference, if present, will be detected.2. The selection of the reference sediment: The mean and associated variability in organismresponses to a reference sediment can vary as a function of where and when the referencesediment is collected. The probability of classifying a dredged material as statistically differentthan the reference sediment will be higher in cases where test organisms perform well in thereference sediment and the variation associated with their response is low.Interpretive Thresholds: When statistical differences are detected between responses of organismsexposed to dredged material and a reference sediment, consideration is then given to what inferencescan be drawn from the presence and magnitude of those differences. One source of information that canbe used in forming such inferences is data on the past performance of the biological test underconsideration. This kind of information can help establish confidence that observed differences are "real"in the sense that they are consistent with previous experience using the test. Inter-laboratory studies canbe used to establish interpretive thresholds for toxicity tests by ensuring that differences are larger thanthe variability that might be expected among different laboratories testing the same sediment. Thisapproach is the basis of current U.S. guidance, which identifies a dredged material as potentially toxicwhen mortality in 10-day amphipod tests is statistically distinguishable from reference sedimentresponses and is 20 percentage points greater in organisms exposed to dredged material (Mearns et al.1986; USEPA/USACE 1998). Another approach establishing interpretive thresholds involves using datafrom specific geographic areas to calculate minimum significant differences (MSD). In a recent survey oftoxicity test results from estuarine sediments in North America, Phillips et al. (2001) calculated the powerto detect and correctly classify samples as ‘toxic’ using 90th percentile MSD based on a comparison tocontrol sediments.In addition to developing confidence that any test response differences observed between dredgedmaterial and a reference sediment are statistically "real," consideration should also be given to44

developing inferences for relating those differences to the potential for ecological impacts. One approachfor forming such inferences uses population models where effects on endpoints measured in a biologicaltest (e.g., changes in survival, growth and reproductive rates) can be related to changes in populationdynamics (e.g., population growth rates or extinction risk) (Bridges and Dillon 1993, Bridges et al. 1996,Bridges and Carroll 2000). Field studies that are designed to test the predictive quality of biological testscan also be used to establish relationships between the results of biological tests and ecologicallymeaningful impacts in natural populations and communities (e.g., McGee et al. (2004)).Developing Cause-and-Effect InformationBecause the responses of organisms in biological tests can be influenced by factors other than thepresence of contaminants, there is strong merit in using supporting information to develop confidence thatany observed responses are being caused by contaminants. Such information can also be used todevelop confidence in conclusions that are based on an absence of response in test organisms, or inmarginal responses that are close to, but don't exceed, interpretive thresholds. Moreover, cause-andeffectinformation that can be used to identify likely causative agents in sediment can help in identifyingcontaminant sources and appropriate pollution control measures. However, because of the complexityinherent to sediment geochemistry and toxicology, identifying clear and certain causative agents insediment, and backtracking to the source, will in most cases prove to be a significant challenge. Recentand ongoing research in this area has produced some relevant tools for developing cause-and-effectinformation. Several relevant approaches are discussed below.Gradient Studies: A powerful approach to establishing a linkage between the contaminants in asediment and biological responses is to compare data collected from sediment samples that are collectedover a gradient of pollution (Porebski et al. 1999). If sediment toxicity increases along the gradient leadingto a (point) source while contaminant concentrations associated with that source also increase, thenstrong evidence exists for linking contamination and the source to the responses observed.Spiked Sediment Toxicity Evaluations: Data from experiments with sediments that are spiked with asingle contaminant can be used to establish inferences about cause and effect. When the concentrationof a contaminant in the dredged material exceeds the concentrations producing an effect in a similar, butpreviously uncontaminated, sediment spiked with that compound, evidence may exist for linking theobserved responses in dredged material to that contaminant. However, the presence of mixtures ofcompounds in a dredged material can complicate this interpretation due to the combined toxicologicalinfluence of all the contaminants. Also, it is difficult to realistically simulate natural processes affectingbioavailability in spiked sediments.Use of Chemical- or Class-Specific Bioassays: The biological tests most commonly used in currentevaluations of sediment provide non-specific information about toxicity, i.e., the responses measured inthese bioassays are not linked to any specific chemical or chemical class. However, a number ofbiological tests are being developed that are based on the use of biomarkers that can be morespecifically linked to a chemical or chemical class. This class of biological tests is discussed in moredetail in Section H. When used in combination with traditional biological tests, these biomarkers could beused to develop inferences about which compounds in a mixture are contributing to any observed toxicity.Use of Chemical Sediment Quality Guidelines (SQG): A number of numerical SQG have beendeveloped for making predictions about the likelihood for toxicity to sediment-associated organismsbased on sediment chemistry data (Wenning et al. 2005), as discussed in Section C. One of the mosteffective uses of SQG is aiding in the interpretation of biological tests and resolving apparent conflictsamong points of information concerned with benthic effects. For example, if one of three toxicity testsprovides evidence indicating the presence of toxicity, but sediment concentrations for all COC are belowlower threshold SQG (e.g., ERLs), then the conclusion that benthic effects are unlikely would bestrengthened by the information provided by SQGs. If, on the other hand, one or more COC exceed EqPbasedguidelines for contaminants that the responding test organism is known to be sensitive to, then theconclusion that effects are likely is supported. Clearly, other information could and should be used to45

esolve these challenges, including information about other potential causes for the observed effects(e.g., test species' sensitivity to sediment grain size distribution, sediment concentrations of ammonia andhydrogen sulfide, the potential presence of unidentified COC, etc.). In this fashion, chemistry data andSQGs can be used to develop cause and effect and other supporting arguments to strengthen or clarifyconclusions.Toxicity Identification Evaluation (TIE): TIE methods make use of biological tests and chemicalmanipulations of a water or sediment sample to isolate and identify the chemicals or chemical classesresponsible for the observed toxicity. Approaches for performing TIEs have been developed for testinginterstial (pore) water and whole sediments (Ho et al. 2002). The TIE approach is composed of threephases: characterization, identification, and confirmation (Burgess et al. 1996). The basic approach toTIE involves evaluating the toxicity of a sample with a biological test, manipulating the sample to removethe potential influence of a specific chemical fraction within the sample, then retesting the sample toevaluate whether any changes in toxicity are evident. The most common applications of TIEs to datehave been to identify the role of ammonia as a causative agent and to identify the role of broad classes ofcontaminants in a contaminant mixture (i.e., metals and organics) (Ho et al. 2002).Several different TIE manipulations can be performed with interstitial water in accordance with themethods described in Burgess et al. (1996), for example:1. Graduated pH. The toxicity of sulphide, organic acids, trace metals, and ammonia (Figure 17) isinfluenced by pH. By manipulating pH, the toxicological influence of these compounds can bechanged, i.e., reduced.2. Chelation. Adding EDTA (ethylenediaminetetraacetic acid) to a test sample results in binding withdivalent cationic metals, resulting in a drop in metal toxicity.3. Oxidant reduction. Adding sodium thiosulphate causes a reduction reaction and consequentlycan reduce toxicity from constituents like chlorine and bromine when they are present in thesample.4. Reversed-phase chromatography. Nonionic organic compounds can be removed from theinterstitial water using a solid phase extraction column.While the use of TIE provides particular promise for developing cause-and-effect information to supportsediment management decisions (see example in Figure 17), there are a number of limitations for themethods in their current form. Complicating factors for TIE approaches making use of interstitial waterinclude changes in metal toxicity due to oxidation during pore water extraction and testing, loss of CO 2resulting in changes in pH, and the potential insensitivity of the method to identifying a role for highlyhydrophobic compounds. The principal limitation for whole sediment TIE concerns the inability todiscriminate beyond broadly defined categories of contaminants (e.g., ammonia, metals, organics (Hoet al. 2002). Information from the limited number of whole sediment TIEs that have been conducted todate suggests that toxicity in marine sediments is most commonly associated with the organiccontaminant fraction, with relatively little evidence for either metal or ammonia toxicity (Ho et al. 2002).Integrating Lines of Evidence into a Weight-of-Evidence DecisionAt least three levels of information integration are necessary to reach conclusions about the risks posedby a sediment. First, points of information within a given LOE must be integrated to characterize exposureor effects within each of the three ecosystem components represented in Figure 16. For example, thesediment-effects line of evidence may include information from three different toxicity tests and criticalbody residue toxicity data for key COC. Incongruities among related points of information (segments ofinformation) must be resolved, e.g., one toxicity test indicates the presence of toxicity and two show lackof toxicity. At this stage of an evaluation, SQG can provide substantial aid in addressing such datainterpretation challenges where apparent conflicts exist among points of information concerned withbenthic effects, as was discussed above.46

10080Survival (%)60402000baselineC18pH7pH7 + C18pH91530 50 100% Interstitial waterFigure 17.An example of the kinds of results produced by a TIE. In this example, a72-hr biological test was performed with the amphipod C. volutator(Stronkhorst 2003). The changes in toxicity observed after pH manipulationsdemonstrate the influence of ammonia to observed toxicity. The additionalreduction observed when organics are removed with solid phase extractionusing a C18 column suggests some role for organics present in the sample.However, in this particular case, all causes of toxicity cannot be accountedfor as unexplained toxicity remains in 100-percent interstitial water adjustedto pH 7 and treated with a C18 columnA second level of integration occurs when the exposure and effects LOE are integrated. For example,contaminant tissue concentrations in field-collected invertebrates and bioaccumulation test organisms(sediment-exposure LOE)) could be integrated with the critical body residue data (sediment-effects LOE)to reach conclusions about risk to the benthic community. This second level of integration feeds the thirdlevel of integration where an overall weight of evidence (WOE) is assembled to address the assessmentquestions and reach conclusions about the nature, extent, and magnitude of risks (Figure 16). At eachlevel of integration, care should be taken to recognize that there are spatial and temporal dimensions toexposure and effects processes. Stated in simple terms, 10 m 2 of contaminated sediment presents lessopportunity for exposure and effect than 10,000 m 2 . Consideration should also be given to controlling theloss of information during the integration process. Summarizing and combining results from multiplesources of information is the principal challenge associated with using WOE approaches in riskassessment. The dual purpose of a sediment assessment is to establish whether potential risks exist andto provide sufficient process-level information to identify where and how the material should be managed.The third level of integration occurs when all of the LOE are considered to characterize the nature, extent,and magnitude of risk. Weight of evidence has been defined as “the process of combining informationfrom multiple lines of evidence to reach a conclusion about an environmental system or stressor” (Burtonet al. 2002). The specific approach for accomplishing this phase of integration will depend on the natureof the assessment questions motivating the assessment and the tolerance of the decision-makingprocess to uncertainties associated with the data and inferences drawn from those data.47

H. Uncertainties and Future DevelopmentsSuccessfully using any analytical tool requires having an appreciation for the uncertainties associatedwith its use. No single test or evaluative tool is able to provide a complete and accurate picture of thecomplexities inherent to evaluating contaminated sediments. Presented below is a brief summary ofsome of the sources of uncertainty associated with applying biological tests to manage dredged material.• Sediment sampling and handling. Biological tests are used to assess very small parts of theenvironment or site of concern. In most cases this assessment will involve removing samples ofsediments and/or water from the field and performing tests on this material in the laboratory. How thesample is taken and handled prior to testing, and the conditions the sample is subjected to during testing,can affect the accuracy and precision of test results. Guidance has been developed by agenciesconcerned with sediment assessment to minimize the degree of artificiality and variability that can beintroduced by sampling and handling procedures (USEPA 2001). Once removed from the environment,samples will undergo geochemical changes that can alter the bioavailability of the contaminants theycontain. Well-formulated guidance and procedures for sampling and handling environmental sampleshave been developed to minimize this source of uncertainty in sediment assessment.• Inter-specific extrapolation: Because it is logistically impossible to directly test the potential for aspecific dredged material to have an adverse effect on every species in the vicinity of a disposal site,concerns about potential impacts must be satisfied by assessing effects on a subset of organisms thatare likely to be exposed. In most cases this subset will be composed of a relatively small number of taxain comparison to the number residing at the site of concern. This fact motivates the decision to select testorganisms that are among the most sensitive to the presence of contaminants. If the test indicates thatthe material poses little risk to the subset of sensitive taxa used in a battery of tests, then the material isunlikely to provoke responses in the less sensitive remainder. However, uncertainty is introduced to theevaluative process because of a lack of complete understanding of the contaminant sensitivity of allspecies that are likely to be exposed. This uncertainty is minimized by testing with multiple species thatare closely associated with the sediment and have a demonstrated sensitivity to the contaminants ofconcern.• Temporal scales: Biological tests provide only a brief snapshot of the processes affectingcontaminant exposure and effects in sediments. For example, most laboratory-based biological testsexpose organisms for a few days to at most a few weeks of time. However, exposures at field sites canlast much longer. The snapshot approach also limits consideration of changes in toxicity with time, e.g., areduction in toxicity over time when sediments are removed from sources of contamination at a dredgingsite and relocated to an area for disposal.• Spatial scales: The spatial scales over which the potential for effects are evaluated are limited, ingeneral terms, to the spatial dimensions of the experimental unit under examination, e.g., a glasscontainer in a laboratory. The confined nature of laboratory tests may over-estimate the extent ofexposure and effects given that the organism’s movements are restricted to the material being tested andwater movement (i.e., flow) is minimal. For this reason the information provided by sediment toxicity testsis most relevant to hazard or effects assessment. Making statements about the risk associated with asediment will require information about the extent and magnitude of exposure that organisms are likely toexperience at the site. The small spatial scales that are convenient for laboratory experimentation alsoprevent direct examination of specific biological components of the ecosystem, e.g., large, mobilespecies.• Biological/ecological scales: Relating the effect observed during a biological test to impacts ofconcern at a disposal site represents a formidable challenge. In most cases the impacts of concern atdisposal sites occur at levels of ecological organization that are well beyond what can be convenientlymeasured in controlled laboratory tests. Biological tests most commonly measure effects on individualorganisms whereas the ecological impacts of concern occur at the level of populations and communities.Relating a specific percent reduction in survival or reproduction observed in a biological test to the48

potential for an impact on the viability of a population of those organisms inhabiting a disposal site is acomplex problem (Bridges and Dillon 1993). In a similar fashion, using results of tests designed tomeasure the potential for contaminants to bioaccumulate in tissues of sediment-dwelling organisms tomake statements about impacts on organisms at higher trophic levels requires the use of methods thatintroduce their own sources of uncertainty (i.e., mathematical models). Tools are being developed tostrengthen the ability to make these kinds of projections (e.g., population and trophic transfer models);however, uncertainties will remain.• Experimental variables: Test organisms will respond positively and negatively to sedimentaryfeatures and experimental variables that are unrelated to the degree of contamination present in asediment. The preference/sensitivity of some test organisms to the grain size distribution of a sediment isperhaps the best known example of such a response (DeWitt et al. 1988); however, organisms willrespond to other characteristics of the sediment or experimental system in a manner that may mimic ormask responses to contaminants. The amount of food supplied to organisms in tests that requiresupplemental feeding (Bridges et al. 1997) and the presence of suspended solids in elutriate tests(Bridges et al. 1996) can confound the interpretation of test results or mask the presence of toxicity. Thissource of uncertainty can only be minimized by developing a thorough experimental understanding of thebiology and ecology of the test organisms used in biological tests.• Statistical error: Biological tests rely on hypothesis testing and statistical tests to compare dredgedmaterials to a control or reference condition. As such, biological tests are subject to so called type I andtype II errors. Type I error is the probability of rejecting the null hypothesis when in fact it’s true. This erroris chosen by the investigator when the significance level is selected, e.g., an α level equal to 0.05 meansthe probability of a “false positive” is 5 percent. The likelihood for a “false negative” is the type II error, orthe probability of accepting a null hypothesis when that hypothesis is in fact false. The probability of atype II error is β, where 1-β equals the power of the test. Concerns about committing type II errors mustbe addressed during the design and development phase of a biological test by ensuring that adequatereplication is prescribed to detect a desired magnitude of effect.Notwithstanding the uncertainties discussed above, biological tests provide the most direct and certainmeans for assessing the potential for toxicity and contaminant bioavailability in sediments. The sources ofuncertainty associated with biological testing range from those that can be minimized, e.g., by carefullyfollowing well-developed procedures for conducting biological tests, to those that are irreducible.However, between these two polar extremes lie sources of uncertainty that are the focus of current andfuture research.Future DevelopmentsResearch and development efforts are being focused to reduce the uncertainties and costs associatedwith assessing dredged material. Both the number and complexity of environmental questions beingposed to port and dredged material managers have steadily increased in recent years, and this trend willlikely continue in the future. Ongoing research is being used to provide answers to these questions and toaddress sources of uncertainty in the assessment and decision-making process. Research is also beingdirected at reducing the costs of dredged material assessments, which have also steadily increased overtime. Developing screening methodologies and other cost-saving measures has increased in importanceas more tests, including more sophisticated analytical approaches, are required to address concernsregarding the management of contaminated sediments.• Quantitative exposure assessments: Reaching confident conclusions regarding the potential forenvironmental impacts of concern at or in the vicinity of a dredged material management site requiresassessing the likelihood that receptors of concern will be exposed to contaminants in the dredgedmaterial. Sediment toxicity tests provide information about toxicity or hazard to sediment-dwellingorganisms. However, exposure conditions for benthos at a management site may differ significantly fromthose occurring in the laboratory. Understanding this difference will require information about themanagement site, including hydrodynamics (is the site dispersive or depositional?), the areal extent of49

coverage once the material is deposited, how organisms at the disposal site interact with the sedimentand overlying water, etc. The complexities at issue are even greater in the case of evaluating concernsfor fish and wildlife at a management site. Assessing the potential for impacts of concern on suchreceptors requires information about the bioaccumulation potential of contaminants from the dredgedmaterial (e.g., results from a bioaccumulation test), how receptors use the management site, and howspecific contaminants will move through the local food web. Mathematical models are increasingly beingused to evaluate the movement of contaminants within food webs at aquatic sites and the potential forimpacts on resources above and beyond the management site (Linkov et al. 2001). The U.S. Army Corpsof Engineers has recently developed a modeling system that can be used to evaluate effects within foodwebs when evaluations require assessing bioaccumulation as an exposure pathway(http://el.erdc.usace.army.mil/trophictrace/index.html).• Pathogens in dredged material: Microbial pathogens in aquatic systems can contaminate drinkingwater supplies and/or shellfish and are responsible for hundreds of beach closure events annually. Theproximity of sediments to be dredged to sources of pathogens, e.g., sewage outfalls and agriculturalrunoff, and the presence of conditions favorable for the long-term viability of microbes, makes pathogensin dredged material a matter of growing concern. Unfortunately, standard microbial methods in useworldwide fail to provide adequate information upon which to base management decisions. Somepathogens of concern are not associated with the widely used fecal coliform indicator. In addition, somepathogens cannot be cultured from environmental samples using standard media and conditions.Molecular methods are currently being developed to address the deficiencies in current approaches. Themolecular approaches under development are not based on the need to culture the pathogens of concernbut on extracting and analyzing their DNA. The use of gene-probe technology has the potential to providea reliable and highly specific method for detecting a pathogen as well as its virulence potential, i.e., itsability to cause disease (American Academy of Microbiology 2001). When such methods are refined andavailable for widespread use, more credible assessments of pathogens in dredged material will bepossible.• Use of biomarkers: Chemical and biological testing conducted during evaluations of dredgedmaterial can be expensive and time-consuming. Given the large volumes of sediment dredged worldwideto support navigation activities, substantial cost savings could be realized if fast and inexpensivescreening procedures or replacements for more expensive tests could be developed. Biomarkers arephysiological or biochemical responses within a living system that can be measured as a signalassociated with chemical exposure and/or effects (Inouye and McFarland 2000). Cell-based assays arein wide use in the human health industry and are being adapted and developed for environmentalapplications as biomarker-based tests. For example, the P450RGS cell-based assay is being used toscreen for the presence of dioxin-like compounds in sediment (Inouye and McFarland 2000). This systemhas comparable sensitivity to high-resolution mass spectrophotometry but can be performed at a fractionof the cost of traditional analytical methods. This method is currently being demonstrated as an approachfor screening large numbers of sediment samples for the need to conduct more specific chemicalanalysis. Other approaches under development make use of recent advances in biotechnology. DNAarrays, so-called “genosensors,” offer the potential for simultaneously measuring hundreds ofbiochemical responses within a cell or organism by monitoring changes in the activity of specific genes(Inouye and McFarland 2000). Because biological responses to contaminant exposure leading to toxicityshould first be evident as changes in gene activity, monitoring such activity offers the means to screensamples for toxicological potential. Many of the chronic sediment toxicity tests currently in use, or underdevelopment, require weeks of exposure to the sediment of concern. The development of gene-basedscreening tests that could be performed over the course of a few days would provide for substantialsavings in time and costs.50

I. Role of Biological Testing in MonitoringThe role of monitoring has been described in detail in the PIANC report “Management of aquatic disposalof dredged material” (PIANC 1998). Three types of monitoring are distinguished:• Surveillance monitoring: long-term environmental monitoring.• Disposal site monitoring: medium-term, site-specific monitoring.• Operational feedback, (compliance), monitoring: short- and medium-term monitoring of selectedproject elements.• Surveillance monitoring. This aims to provide information for a check on general environmentalquality and is normally performed by national, regional, or local authorities. It often involves the provisionof long-term data sets on factors such as fish health, biodiversity, and contaminant status of waters andsediments. The use of bioassays in such monitoring programs is in its relative infancy, but examplesinclude the use of oyster embryo bioassays on elutriates of sediment from around the UK, and of wholesediment bioassays using Corophium volutator and Arenicola marina as part of the UK’s National MarineMonitoring Program. In the United States, the U.S. Environmental Protection Agency's EnvironmentalMonitoring and Assessment Program (EMAP) provides information on the status of water and sedimentquality (http://www.epa.gov/emap/). Monitoring of this type is aimed at understanding the status of theenvironment, and the integrated impact of a range of human activities on the aquatic environment, andhence lies outside the scope of this report where we concentrate on the impact of dredged materialdisposal.• Disposal Site Monitoring. This form of site-specific monitoring is carried out primarily to checkwhether environmental assessment and permit conditions established prior to the commencement ofdredging and disposal operations are maintained. Such monitoring plays an important role in dredgedmaterial disposal management, and may be required during and/or post disposal. Monitoring provides afeedback loop into the assessment process, and is normally carried out by or at the requirement of theAuthority permitting the disposal. Well-designed monitoring can be a powerful management tool,providing specific evidence to support or modify disposal site management plans and practices. Formonitoring to be effective it must be designed to test assumptions or predictions that were made at theassessment stage, the so-called “impact hypothesis.”• Operational Feedback (Compliance) Monitoring. This is carried out to verify if operations are beingcarried out in the most effective way and to check if they meet the permit requirements. Results of thismonitoring are used on a day-to-day basis to direct the execution of operations and to indicate the needfor improvements or mitigating measures to be applied. Compliance monitoring is often executed by theoperator of the project, under the guidance of the responsible authority, if there is a compliance element.The need here is for techniques that use rapid measurement and direct interpretation of results. To date,most references are for using physical and chemical techniques, for example to measure plumedispersion, but in some instances direct biological measurements may be appropriate.Design of Monitoring Programs to Determine the Impact of Dredged Material DisposalThe nature of the actual, potential, or perceived effects of dredged material disposal will dictate the extentand type of monitoring required. Monitoring is designed to test assumptions or predictions about thebehavior of the dredged material and the receiving environment during and post disposal, i.e., to test the“impact hypothesis.” Monitoring may encompass biological, chemical, and physical components. It isimportant that the scale of monitoring relates to the extent of the perceived problem, and that thecomponents for monitoring relate to the cause for interest or concern.It is outside the scope of this document to deal comprehensively with the design of monitoring programsfor dredged material disposal, since this will encompass the range of physical, chemical, and biologicalmeasurements required. However, it should be noted that monitoring of biological systems is often a key51

component of such programs. The programs aim to gain an understanding of the response of organismsin the field situation, to check that the conclusions reached during the assessment of the dredgedmaterial were correct, and to provide feedback into the assessment process. In addition to the collectionof samples of water or sediments and the application of the types of techniques described in Section D,field observations are important. Biological observations may include studies of benthic infauna andepifauna, fish populations, and studies of fish disease. Information on physical sediment characteristicswill also be required to enable interpretation of the biological data. Since the effects being observed areoften subtle, it is important that comparisons are made to a reference site, and that sensitive techniquesare chosen which are capable of detecting subtle changes reliably and consistently. The techniquesshould also be capable of distinguishing changes due to the physical impact of the disposed materialsfrom influences due to chemical contaminants. GIPME (2000) has commented that field observations ofbiological effects in contaminated sediments seldom give insight into which particular contaminants areinvolved and whether their effects have been enhanced through interactions with natural stressors.Studies have revealed marked seasonal differences in the susceptibility of benthic organisms to a givendegree of sediment contamination, and hence timing of monitoring programs is important. Benthiccommunities are subject to many perturbations, the majority of which are of natural origin, and henceestablishing cause-and-effect relationships can be very difficult. This argues for careful design andexecution on monitoring programs if they are to achieve their aim of validating impact assessments. Inmost studies of dredged material disposal reported to date, the observed changes have been associatedwith physical impacts, and relatively few examples of biological change being caused by chemicalcontamination due to aquatic disposal of dredged material are evident.52

J. ConclusionsEnvironmental assessments of dredged material are conducted to determine the likelihood that proposeddredging operations could result in adverse impacts to the environment. Performing such assessmentsrequires collecting information on the complex physical, chemical, and biological nature of sediment. Thecomplex nature of sediments, to a large degree, constrains an assessor’s ability to make sufficientlyaccurate predictions about the potential for adverse biological impacts from dredging operations usingphysical and chemical data alone. Biological tests provide essential information regarding thebioavailability of contaminants in a dredged material as well as the potential for that material to produceadverse responses in exposed organisms. The use of biological tests can increase the certainty of ourassessments. However, even in simple cases, ill-defined complexities and uncertainties will remain. Thisfact necessitates the use of a guiding framework for using biological tests to assess dredged material thatstructures how the information gained from biological tests is used to reach management decisions.Ultimately, the effectiveness of decision-making will depend on the ability to integrate information frommultiple lines of evidence related to describing the potential for adverse impacts.International conventions and national laws require that dredged material be assessed for its potential tocause biological impairment. Broad scientific consensus has been reached that biological tests are acritical component of such assessments. For those countries or agencies with limited experience usingbiological tests, the most direct way forward would be to seek out well-developed and validatedapproaches being used by others. Experience gained in applying and adapting approaches used byothers will facilitate local efforts to develop biological tests using regionally relevant species andapproaches.Research concerning biological tests and their use in decision-making should be directed in four principalareas. First, research should be focused on expanding the relevance of biological tests for the full rangeof compounds and types of effects (e.g., endocrine disruption) of concern during evaluations of dredgedmaterial. Additional study and attention should also be given to the role of modifying factors and thedevelopment of approaches to aid in the interpretation of biological tests. Second, efforts should bedirected to developing more definitive methods for assessing exposure. Biological tests are mostcommonly used to provide information about hazard or the potential for effect. Reaching more certainconclusions about the risks posed to the environment requires having information about what exposureconditions are likely to be in the field, e.g., at the disposal site. Such exposure research would includestudy of the processes controlling contaminant bioavailability in sediments as well as methods forcharacterizing contaminant bioaccumulation and approaches for interpreting and using bioaccumulationdata to make statements about risk. Third, research efforts should be invested in validating biologicalmethods for predicting the likelihood for biological impairment. These efforts could include a range offield-oriented monitoring studies designed to test the accuracy of assessments made a priori. Suchresearch will serve to strengthen the inferential linkage between biological tests and impacts in the field,increase confidence in the decision-making process and provide necessary feedback to the assessmentprocess itself. Fourth, more work is needed on developing effective methods for integrating the diverseinformation collected during environmental assessments of dredged material. Conclusions about thepotential for biological impairment, or risk, are generally based on multiple lines of evidence. Moreformalized and structured approaches for integrating and processing this information to make decisionsbased on the weight, or preponderance, of evidence must be developed to avoid the frustration andinefficiency ad hoc decision-making produces.Structured use of biological tests will improve the quality of dredged material assessments and theeffectiveness of management decisions. Biological assessments of dredged material should begin withdeveloping a comprehensive conceptual model for the dredging project that leads to formulating specificassessment questions and then selecting biological tests to answer these questions. This progression ofactivity will help to ensure that assessments are conducted in a logical fashion that is driven by theinformation needs of the assessor and decision maker. Applied in this manner, biological tests willprovide essential and timely information for decision-making.53

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U.S Army Corps of Engineers. (2002). “Evaluation of dredged material proposed for disposal at island,nearshore, or upland confined disposal facilities — Testing Manual,” ERDC/EL TR-03-1, U.S. ArmyEngineer Research and Development Center, Vicksburg, MS.U.S. Environmental Protection Agency (USEPA). (2002). “Methods for measuring the acute toxicity ofeffluents and receiving waters to freshwater and maine organisms,” EPA-821-R-02-012, Washington,DC.U.S. Environmental Protection Agency (USEPA). (2002). “Short-term methods for estimating the chronictoxicity of effluents and receiving waters to freshwater organisms,” EPA-821-R-02-013, Washington,DC.U.S. Environmental Protection Agency/U.S. Army Corps of Engineers. (1991). “Evaluation of dredgedmaterial proposed for ocean disposal, Testing Manual,” EPA-503/8-91/001, Washington, DC.U.S. Environmental Protection Agency/U.S. Army Corps of Engineers. (1998). “Evaluation of dredgedmaterial proposed for discharge in waters of the U.S. – Testing Manual,” EPA-823-B-98-004,Washington, DC.U.S. Environmental Protection Agency/U.S. Army Corps of Engineers. (2001). “Methods for assessing thechronic toxicity of marine and estuarine sediment-associated contaminants with the amphipodLeptocheirus plumulosus,” 1st ed., EPA/600/R-01/020, Washington, DC.Water Environment Federation. (2002). Handbook on sediment quality. Water Environment Federation.Alexandria, VA.Wenning, R., Ingersoll, C, Batley, G., and Moore, D. (2005). “Use of SQGs and related tools for theassessment of contaminated sediments,” SETAC Press, Pensacola, FL.Williams, L. G., Chapman, P. M., and Ginn, T. C. (1986). “A comparative evaluation of marine sedimenttoxicity using bacterial luminescence, oyster embryo and amphipod sediment bioassays,” Mar.Environ. Res. 19, 225-249.62

L. Appendix. Case StudiesThree case studies are summarized in this section to provide examples of the use of biological testing inthe assessment of dredged material for open-water disposal and for the monitoring of environmentalimpacts associated with such operations.In all cases biological measurements have been used to supplement other information (e.g. physical,chemical, hydrographic, background) to characterize the dredged material and the disposal site. The useof biological measurements in conjunction with other information types and LOE provides acomprehensive approach to the evaluation of the suitability of dredged material for open-waterplacement, the selection of the disposal site and disposal methods, and the monitoring of any associatedimpacts.63

Case Study 1New Haven Harbor, Connecticut, USAPrepared by Tom Fredette, New England District, U.S. Army Corps of Engineers (USACE)New Haven is located on the shores of Long Island Sound in the northeastern portion of the UnitedStates. The harbor is served by a 10.7-m-deep channel about 7.2 km long and varying in width from 120to 240 m. Adjacent to the channel is a 10.7-m-deep turning basin and a 5-m-deep anchorage. Threesmaller channels lead up the tributary rivers.New Haven Harbor is the second busiest port in the six-state New England region, having 24 commercialterminals. Products handled by the terminals include petroleum products, scrap metal, lumber, steel,cement, chemicals, and general cargo. New Haven Harbor is also important for recreational activities andcommercial fisheries use. Oyster harvesting and lobster fishing are the primary commercial fishingactivities in the harbor.Need for DredgingIn order to meet the continued need for navigation access to the docking facilities in the harbor, dredgingwas needed to remove the shoals that had formed in the channel since it was previously dredged in1983. The controlling depth of the channel had been reduced to 8.2 m. In order to return the channel andadjacent navigation areas to their authorized dimensions, 1,000,000 m 3 of sediment needed dredging.The area needing dredging extended from the head of the channel to a location just inside thebreakwaters that protect the harbor entrance.Disposal Alternatives AnalysisOpen-water disposal was selected as the most practicable alternative for this project. Preliminarysampling had determined that the sediment was more than 90 percent silts and clays, making itunsuitable for beach nourishment. Creation of salt marshes or islands in the harbor or along the nearbycoastline was incompatible with existing uses (e.g., fishing areas and habitat types) and contrary toenvironmental regulations that minimize the filling of aquatic sites. Upland disposal was also found to beimpractical, both from the standpoint of logistics, which would have required dewatering and trucking ofthe sediment, and of the lack of acceptable sites with sufficient capacity (estimated need of >26hectares). The open-water site proposed for this project is about 8 km from the mouth of New HavenHarbor and has been used for at least the last 50 years for disposal of sediments from this and otherregional projects. Environmental monitoring of the disposal site has shown that the site is suitable for thispurpose, while minimizing environmental impact.Dredged Material CharacterizationTier 1. The first step in characterizing the sediments to be dredged was a review of historical informationfrom the harbor area. The channel had last been sampled prior to maintenance dredging in 1983. Therewere also several nearby individual ship berths that had been tested by their owners for separate permitapplications. Spill records and discharge permits from local industries and municipal wastewatertreatment plants that discharge into the harbor were reviewed. Review of these kinds of data are all partof what is termed “Tier 1” in the evaluation approach used in the United States (U.S. EnvironmentalProtection Agency (USEPA)/USACE 1998). Using the information from these reviews, the list ofcontaminants of concern (COC) was developed (Table 1) and sampling stations were selected.The sediment to be dredged was characterized by taking samples for physical, chemical, and biologicalassessment. Physical and chemical testing was conducted first. The field sampling crew took coresamples to dredging depth at nine stations along the length of the channel where dredging was to occur.Samples were more closely spaced in the inner harbor where the levels of contaminants were expectedto be greater. Physical characteristics of the sediments measured included grain size, percent solids, and64

Atterberg limits. The sediment ranged from 93 to 99 percent silts and clays, with the percentage of solidsranging from 30 to 40 percent.Chemical testing of the sediment was conducted on a suite of heavy metals and organic compounds(Table 1). Because of questionable results from the polynuclear aromatic hydrocarbon (PAH) testing, asecond round of testing was conducted for these chemicals that also included re-analysis of archivedsediment from the first round of sampling. Metals and pesticide results from the first round of testing andPAH results from the second round of testing are shown in Table 2. Only the contaminants measuredabove detection limits are shown. These results showed that metal contamination levels were variablealong the length of the channel with the highest concentrations of arsenic, cadmium, and zinc exhibited atstation A; mercury and lead highest at station I; and copper, nickel, and chromium peaking at station H.PAHs generally showed a decreasing trend along the length of the channel, although some individualPAHs peaked at station H (e.g., phenanthrene, fluorene, and benzo (a) pyrene). The only pesticidedetected was heptachlor epoxide. Polychlorinated biphenyls (PCB) were not detected.Tier 2. Characterization under Tier 2 of the U.S. protocol involves comparison of potential contaminantreleases to water quality criteria and calculation of Theoretical Bioaccumulation Potential (TBP) values.Historical data from other projects were considered acceptable to estimate and compare contaminants towater quality criteria. This analysis concluded that, after allowance for initial mixing, no violations wereexpected. Because the COC list contained both metals and non-polar organic contaminants, andbioaccumulation tests were planned, the TBP analyses were not conducted.Table 1List of Chemical Contaminants Specified forTestingContaminants of ConcernMercuryLeadZincArsenicCadmiumChromiumCopperNickelPolychlorinated Biphenyls (PCB)Pesticides (18)Polynuclear Aromatic Hydrocarbons (PAH)Table 2Dry-Weight Bulk Chemical Results from Sediment SamplesContaminantSample StationsA B C D E F G H I% Fines 93 97 96 96 95 97 97 99 98Metals data reported as mg/kgMercury 0.15 0.21 0.18 0.1 0.19 0.22 0.24 0.24 0.28Lead 67 98 32 47 90 100 80 98 106Zinc 595 174 136 81 101 440 117 218 321Arsenic 13.8 0.56 0.86 0.12 0.03 12.6 3.9 1.4 1.5Cadmium 7.7 0.94 3.1 2.9 4.2 1.1 3.9 1.1 0.76Chromium 163 168 168 266 320 220 278 318 16265

Copper 109 99 111 279 260 340 258 420 149Nickel 45 75 82 71 36 76 96 181 60Organic data reported as mg/kgHeptachlor Epoxide 0.46 1.42 1.79 1.94 1.39 0.62 0.82

no accumulation of any of the contaminants in the bivalve and polychaete tissues from the compositesamples to levels greater than the reference test animals.Table 3Mean Percent Survival in the Acute Toxicity and BioaccumulationTestsSample% Survival10-Day Amphipod 28-Day Polychaete 28-Day BivalveControl 92.2 91.5 93.3Reference 86.6 90.0 94.6Composite 1 51.0 88.0 90.0Composite 2 81.3 93.0 90.6EvaluationSediments from the inner harbor, represented by stations A-D, were determined to be unsuitable forunconfined open-water disposal because of the toxic response observed in the amphipod test. Sedimentsrepresented by stations G and H were found to be suitable for unconfined open-water disposal basedupon the results of the biological testing. Sediments represented by stations E, F, and I were alsodetermined to be suitable for unconfined open-water disposal. Regulators had agreed that testing resultsof the A-D and G/H composites would represent worst-case conditions for the harbor. Because stationsE, F, and I had contaminant concentrations that were generally lower than either of the two biologicallytested composites, a decision was reached that these sediments could also be dredged and disposedwithout restriction.Management DecisionsCapping of the sediments from the inner harbor at a nearby open-water disposal site in Long IslandSound was selected as the most practical way to minimize potential adverse impacts from thesesediments. To maximize cap success, a location at the open-water disposal site that was surrounded bypreviously created sediment mounds was selected. The presence of these topographically higherfeatures was used to limit the lateral spread of the New Haven unsuitable material so that the depositcould be more easily capped. This bowl-like feature on the seafloor had been intentionally created for thispurpose through planned management of the disposal site (Fredette 1994). To cap the unsuitablesediment, the sediment from the outer harbor was used. This resulted in 590,000 m 3 of sediment from theinner harbor being capped by 569,000 m 3 from the outer harbor (volumes based on barge estimates).Impact HypothesesThe impact hypotheses from this project included both the response of the marine benthic community tothe disposed sediments and the success of the cap operations. First, it was expected that the bowl-likefeature of historic disposal mounds would help to limit the spread of the sediments. This would enable thecapping to occur using a smaller volume of sediment than would normally be necessary without suchlateral confinement. The second expectation was that the cap could be successfully placed over the innerharbor sediment. The third expectation, or prediction, was that once disposal was completed, the marinebenthic animals would recolonize the sediments and develop into a community similar to referencesediments in two to three years. This last expectation was based on the tiered testing, which is designedto predict response of the biological community. Therefore, if no adverse effects are observed in thelaboratory tests, then the sediments should be environmentally suitable after disposal. These impacthypotheses were the basis for monitoring at the disposal site during and following the dredging anddisposal.67

Project ComplianceA USACE contractor dredged the harbor according to specifications prepared for the project. Thesespecifications identified the sediments that needed to be capped and the sediments to be used for a cap.USACE inspectors and a hydrographic survey crew were on site to observe and review the work of thecontractor. Representatives of environmental resource agencies also made visits to the site to observethe work in progress. In addition, every barge disposal event at the open-water site was observed by anindependent certified disposal inspector who rode the tugboat to and from the dredging site.MonitoringMonitoring of the project included both construction monitoring and long-term monitoring at the openwaterdisposal site. Construction monitoring included a baseline bathymetric survey of the seafloor wherethe sediment was to be placed, interim surveys during placement of the sediment needing capping and ofthe cap, and a post-cap survey (Fredette 1994). Long-term monitoring was conducted under an umbrellaof a tiered design (Fredette et al. 1986, Germano et al. 1994) and has included additional bathymetricsurveys, coring, sediment profile camera photos, and sediment toxicity testing (Morris et al. 1996, Morris1997, 1998). Additional samples and solid phase toxicity tests using field-collected sediments, taken by aseparate study, have confirmed the benthic community recovery and lack of acute toxicity of the deposit(ENSR 2000, 2001). Benthic community recovery serves as an early-warning indicator of potentialadverse effects. Recolonization on this mound has been somewhat lower than expected, though this isbelieved to be a function of both the high organic component of the sediment combined with effects ofregional hypoxic events that occur seasonally in Long Island Sound. This conclusion has been supportedby the follow-on toxicity testing that was done on sediments collected from the mound; however,monitoring of the mound is continuing and a management action to add sediment from other projects tothe mound is being considered as a conservative measure.ReferencesU.S. Army Engineer District, New England (ENSR). (2000). “Sediment toxicity testing summary report,”prepared for U.S. Army Engineer District, New England, and U.S. Environmental Protection Agency,Region 1, Report LIS-2000-LO2-B,Tx. Concord, MA.U.S. Army Engineer District, New England (ENSR). (2001). “Sediment quality triad report,” prepared forU.S. Army Engineer District, New England, and U.S. Environmental Protection Agency, Region 1,Report LIS-2001-AO9-BC, SC Tx. Concord, MA.Fredette, T. J., Anderson, G., Payne, B. S., and Lunz, J. D. (1986). “Biological monitoring of open-waterdredged material disposal sites,” IEEE Oceans '86 Conference Proceedings, Washington, DC.,September 23-25, 1986, 764-769.Fredette, T. J. (1994). “Disposal site capping management: New Haven Harbor,” Proceedings of theConference Dredging '94, November 1994, Orlando, FL, 1142-1151.Germano, J. D., Rhoads, D. C., and Lunz, J. D. (1994). “An integrated, tiered approach to monitoring andmanagement of dredged material disposal sites in the New England region,” DAMOS ContributionNo. 87, U.S. Army Engineer Division, New England, Waltham, MA.U.S. Environmental Protection Agency/U.S. Army Corps of Engineers (USEPA/USACE). (1998).“Evaluation of dredged material proposed for discharge in waters of the U.S. - Testing manual,” EPA-823-B-98-004, Washington, DC.Morris, J. T., Charles, J., and Inglin, D. C. (1996). “Monitoring surveys of the New Haven capping project,1993-1994,” DAMOS Contribution No. 111. U.S. Army Engineers Division, New England, Waltham,MA.68

Morris, J. T. (1997). “Monitoring cruise at the Central Long Island Sound disposal site – September1995,” DAMOS Contribution No. 118, U.S. Army Engineer District, New England, Waltham, MA.Morris, J. T. (1998). “Monitoring cruise at the Central Long Island Sound disposal site – July 1996,”DAMOS Contribution No. 120. U.S. Army Engineer District, New England, Concord, MA.69

Case Study 2Monitoring Disposal of Capital Dredged Material off the Thames Estuary, UKPrepared by Lindsay Murray (CEFAS, UK) based on Rees et al. (2003)BackgroundThe disposal of dredged material arising from port expansion to accommodate larger vessel sizes orincreased trade can pose significant environmental challenges because of the large amounts of dredgedmaterial that may be generated over a relatively short space of time. The conventional managementoption has been sea disposal, for which licenses are issued by the UK Department for Environment, Foodand Rural Affairs under the Food and Environment Protection (FEP) Act (1985), following a satisfactoryoutcome to a risk assessment of the environmental consequences.The LocationThe ‘Roughs Tower’ disposal site is located in shallow water (10-20 m) off the Thames estuary, UK, andis characterized by relatively strong tidal currents (>1m.sec -1 on spring tides) and periodic exposure to theinfluence of wave action at the seabed.History of UseThe site has been in use for many years as a recipient for maintenance dredged material and (until 1996)sewage sludge, as well as periodically for large quantities of capital dredged material arising from earlierport developments at Harwich and Felixstowe, nearby. In 1998, major port expansion at Harwich resultedin the need to dispose of about 32 million wet tons of dredged material.In the build-up to the capital operation, significant effort was devoted to identifying possible alternativeuses of the dredged material, in particular to counter the effects of net erosional regimes in the adjacentStour and Orwell estuaries, and to replace intertidal habitat as a result of port development. A number ofschemes were subsequently implemented, and are the subject of ongoing evaluation, both by theindustry and regulatory interests. However, sea disposal was the only realistic option for the majority ofthe dredged material (some 29 million tons, much of which consisted of stiff clay) and this was eventuallylicensed for sea disposal at the Roughs Tower site.The ProblemConcerns over the dispersive capacity of the local environment in the vicinity of the disposal siteincreased in recent years, especially in relation to the development of a nearby crustacean fishery. Theproblem was accentuated by periodic use of the site for the disposal of large amounts of material over arelatively short space of time. Therefore, the proposed capital deposit, commencing in 1998, carried a riskof exceeding the dispersive capacity of the site, if the disposal operation were to be licensed to proceedin the conventional way.The SolutionAs a result of the above concerns, approval of the application for sea disposal was subject to thecondition that it would be accompanied by effective closure of the site. Additionally, the disposal operationwas to be conducted in such a way as to promote containment of the material within the licensedboundary, and a final sprinkling of gravel was intended to enhance the suitability of the habitat forcolonization by commercial shellfish. The disposal operation commenced in November 1998, and wascompleted in March 2000.Impact HypothesesImpact hypotheses were as follows:70

1. Containment of the majority of the deposited material within the site would result in a measurablebut acceptable decrease in water depths, which would pose no hazard to shipping.2. Physical and biological changes to sediments arising from the 1998/2000 deposit would belimited to the immediate vicinity of disposal.3. Benthic fauna at the disposal site would be adversely affected, but would recolonize relativelyrapidly (i.e., within months) and would be structurally comparable to adjacent assemblages within3 years.4. Disposal would not give rise to significantly enhanced contaminant concentrations in sediments inthe vicinity of the site.5. Following stabilization, the deposited material would have a neutral or even positive impact oncommercial shellfish resources.In order to test these hypotheses, a multi-disciplinary monitoring program was initiated by the regulatoryauthority and by the industry.Outcome of Monitoring/Testing of Hypotheses1. Containment of the majority of the deposited material within the site would result in a measurable butacceptable decrease in water depths, which would pose no hazard to shipping.Containment of the majority of the dredged material was facilitated by the initial construction of abund, involving the placement of consolidated clay and rock along the western perimeter of thedeposit area. Following sequential infilling with dredged material, the area was then closed off by thedeposition of more consolidated material along the eastern perimeter.Monthly bathymetric surveys by the licensee (Harwich Haven Authority) during disposal, and lessfrequent surveys thereafter, served a dual purpose of providing an indication of the buildup ofmaterial at the seabed, and its relative stability in response to tidal currents and wave action.Following the cessation of disposal, the seabed presented a relatively even profile at water depthswhich posed no hazard to shipping. A side-scan sonar survey conducted by CEFAS in 2001 providedindependent confirmation of the integrity of the bunded area some two years after initiation ofdisposal, indicating that the bulk of the deposited material was still retained within the licensed site.2. Physical and biological changes to sediments arising from the 1998/2000 deposit would be limited tothe immediate vicinity of disposal.Sediments in this part of the outer Thames estuary are naturally heterogeneous in nature, andparticle size characteristics can differ markedly on small spatial scales. This accounts for thesignificant within-station variability in mean grain size along a transect of stations through the disposalsite. Overall, there has been a net coarsening of sediments at the disposal site both as a result ofrecent and historical disposal activity.During recent disposal, and in its immediate aftermath, the benthic fauna inhabiting these sedimentswas reduced, but not absent, at stations within and immediately adjacent to the site. The outcome ofa survey conducted in June 2001 showed a marginal (but not significant) increase in numbers of taxaat the disposal site, and a significant increase at two stations to the southwest. There was also asignificant increase in densities at the disposal site, and at two stations to the southwest, in June2001, which was largely accounted for by a recent settlement of the sand-mason worm Laniceconchilega. The post-cessation increases in numbers of taxa and densities to the southwest of thedisposal site suggest that, historically, the fauna here may have been adversely affected bydispersing fine particulates, especially those arising from the disposal of maintenance dredged71

material. These increases also indicate that, to date, ongoing processes of erosion and then transportof the finer component of the recently deposited capital material are insufficient in scale andmagnitude to sustain the apparent inhibitory effect of earlier disposal activity.3. The benthic fauna at the disposal site would be adversely affected, but would recolonize relativelyrapidly (i.e., within months) and would be structurally comparable to adjacent assemblages within 3years.Some 14 months after cessation of disposal, there is evidence of recolonization of sediments withinthe disposal site; however, the diversity is still reduced compared with similar sediments nearby.Therefore, the fauna could not yet be considered to be structurally comparable to adjacentassemblages, and annual monitoring is continuing until there is evidence that a new equilibrium statehas been reached.4. Disposal would not give rise to significantly enhanced contaminant concentrations in sediments in thevicinity of the site.The presence of relatively low levels of trace metal contaminants was established through analysesof samples of the material prior to disposal, as part of the licensing procedure. The outcome of fieldsampling confirmed that, as expected, contaminant concentrations in the vicinity of the disposal sitewere not significantly enhanced following disposal.5. Following stabilization, the deposited material would have a neutral or even positive impact oncommercial shellfish resources.Seven groups of five prawn pots (small fine-meshed, small entrance pots for the common prawnPalaemon serratus) have been hauled weekly since July 2000 and the contents recorded. Thegroups are located at six sites within the boundary of the Roughs Tower disposal site and theseventh is on nearby lobster ground to the east. The catch of lobsters (accumulated over a one-yearperiod from July 2000 to July 2001) ranged between 6 and 34 percent of the catch of lobsters at thenearby control site. Similarly, the catch of edible crabs ranged between 31 and 64 percent of thecatch at the control site. It should be noted that the gear only catches small animals due to thelimiting size of the entrance.Information to date provides encouraging evidence of the suitability of the benthic habitat within thedisposal site for these commercial shellfish species. Additional catch data are required to establishwhether population sizes of juveniles have stabilized at the disposal ground relative to the nearbycontrol site and, over a longer time period, to determine the extent to which these findings aretranslated into enhanced catches within the commercial fishery.ConclusionsThe results to date appear to confirm earlier predictions concerning containment of the recently depositedmaterial, and the localization of physical and biological impacts arising from this recent activity to theimmediate vicinity of disposal. Furthermore, there is evidence of amelioration of these impacts over time,as evidenced by the recolonization of surface sediments by the benthic fauna, and the presence ofappreciable densities of juvenile crabs and lobsters at the disposal site. This suggests that the approachfor managing this large capital disposal operation has been effective. Monitoring of the sediments and thebenthic fauna at the Roughs Tower disposal site will continue, in order to establish the time-scale forattainment of a new and acceptable equilibrium state.ReferencesGreat Britain-Parliament. (1985). “Food and Environment Protection Act, 1985,” Chapter 48, HerMajesty’s Stationery Office, London.72

Rees, H. L., Murray, L. A., Bolam, S. G., Limpenny, D. S., and Mason, C. E. (2003). “Dredged materialfrom port developments: A case study of options for effective environmental management,”Proceedings, 28th International Conference on Coastal Engineering. World Scientific Inc., 3616-3629.73

Case Study 3A Case Study of TBT in England and WalesPrepared by Lindsay Murray, CEFAS, UKIntroductionIn the United Kingdom, the disposal of dredged material at sea is often the most cost-effective means ofremoving sediments from nearshore environments. Some long-established disposal grounds havetherefore been exposed to continual deposits, potentially changing the receiving environment physically,chemically, and biologically. Disposal grounds have been monitored for many decades (Rees et al. 2001)to assess these changes, but more recently a number of additional studies have been conducted. Thecase study presented here focuses on the problem of TBT in sediments, especially paint-derived TBT,and utilizes a range of biological effects techniques to assess the survival, feeding, and behavior ofmarine/estuarine species continuously exposed to TBT in rivers and at a dredged material disposalground. This project meets many of the aims of OSPAR and provides information to assist with decisionmakingunder the UK legislation, the Food & Environment Protection Act (Great Britain Parliament 1985).Key IssuesSeveral areas in England and Wales have elevated levels of TBT in river and dock sediments. Perhapsthe most important, in terms of exceedance of guidelines, is contamination in the lower reaches of theRiver Tyne. Recent refusals of licenses for sea disposal have been based on TBT levels being detectedbetween 1-100 mg kg -1 in river sediments, as well as some concerns of contamination at the Tyne Dockdisposal ground. To assess the extent and nature of the problem, monitoring at the Tyne Dock disposalground included special surveys offshore and some inshore work.Case Study: Tyne EstuaryThe River Tyne has historically been the focus for ship building in the UK. As a consequence, TBT fromantifouling paints and other discharges (hose-down water and dry-dock float water) has been detected inthe water column and sediments at elevated levels. TBT occurs in sediments in three broad categories(1) large paint chippings, (2) small paint particles derived from high pressure hosing of copolymerformulations, and (3) TBT adsorbed to the sediments. Some possible biological effects of TBT as paintderivedmaterial include endocrine disruption, e.g. imposex (Matthiessen and Gibbs 1998); shellthickening in Pacific oysters (Crassostera gigas) (Waldock and Thain 1983) and benthic communitychange (Rees et al. 1999).The risks posed by TBT adsorbed to sediments have been well documented (Waldock and Thain 1983;Valkirs and Stallard 1987; Champ and Seligman 1996); however, the implications of paint-derivedmaterial from historic TBT inputs has not been addressed. Guidance is therefore sought on how tomanage sites where TBT remains a problem, particularly where TBT exists as paint flakes and where seadisposal of sediments from the site has been refused.TechniquesThis case study considered a number of biological tests including caged dogwhelks inshore and at thedisposal ground (Smith et al. 2005), meiofauna microcosm experiments (Schratzberger et al. 2002), andspiked sediment toxicity tests using Arenicola marina and Corophium volutator (International Council forthe Exploration of the Sea (ICES) 2002a,b).74

Results and DiscussionCaged studies using dogwhelksCaged whelks, Nucella lapillus, and mussels were deployed at four sites in the inner estuary and twosites at the mouth of the R. Tyne (i.e. non-impacted) for 6 months. Imposex was measured using theOSPAR JAMP guidelines (Gibbs et al. 1987; Oehlmann et al. 1991) and results are shown in Figure 1.Highest incidences of imposex (100 and 90 percent, respectively) were recorded at a busy dock (11-12km upstream of the river mouth) refurbishing ships more than 25 m in length, and a site by a smallpontoon near the south bank some 2 km from the river mouth. Highest measured TBT concentrations(0.03 - 0.05 mg kg -1 ) in female whelks corresponded with highest incidence of imposex. Results showedthat TBT accumulated over time in mussels and therefore increased the overall TBT burden in whelks.The biological impact at the end of the 6-month study was high imposex induction in the inner estuary(Smith et al. 2005).A second cage study using Nucella and mussels was carried out on the Souter Point (Outer) dredgedmaterial disposal ground. Cages were deployed for three months in a transect across an area known tobe contaminated with TBT (i.e. at concentrations of between 0.1-0.2 mg kg -1 in surficial sediments; Reedet al. 2002). Dogwhelks showed no signs of imposex induction at the end of the three-month period andthe levels of TBT and DBT in both mussels and dogwhelks were not significantly different from thecontrols. This result may be a consequence of limited exposure time that was caused by fishing activity inthe area.Microcosm Experiments Using MeiofaunaMicrocosm experiments were designed to assess the survival rate of nematode species exposed todifferent concentrations of paint-derived TBT in sediments and to assess migration and survival rates ofnematode species during deposition of clean and TBT-contaminated sediment. Adverse effects onnematode assemblages (i.e. species diversity and richness) were found in highly contaminatedsediments (>10 mg kg -1 ). Exposure time was critical as TBT was slowly but continuously leached from thepaint particles into the sediment pore water. Route of exposure for nematodes was through theirpermeable cuticle and by direct ingestion of paint particles with food. Results of the deposition experimentindicated an immediate and dominant effect of burial on most nematode species, although this wasspecies-specific. Species that were successfully able to cope with the deposition and were also presentin TBT-contaminated sediment (e.g. Cyatholaimus gracilis), suffered by experiencing a change inindividual biomass, indicating that larger, mature animals were more resilient to TBT contamination thansome of the smaller juveniles.Spiked Sediment Toxicity TestsBoth acute and sublethal toxicity tests using Arenicola marina and Corophium volutator were conductedusing sediments spiked with paint-derived TBT. A. marina survived all concentrations (0.1- 10 mg kg -1 ) inthe acute test while C. volutator survived concentrations

Figure 1.VDSI incidence of imposex and RPSI in populations of caged dogwhelks76

Figure 2.Sublethal effect of paint-derived TBT on casting of Arenicola marinaConclusionAs can be seen from the results of these experiments, the biological effects of paint-derived TBT are notseen as quickly as those shown for TBTO. However, long-term impacts of paint-derived TBT remain aproblem, especially at some dredging sites around the UK (e.g., Tyne) where TBT levels are high (greaterthan 10 mg kg -1 ), and where TBT leaches from paint particles in the sediment. Sea disposal licenses willcontinue to be refused for the most contaminated dredged material, and alternative management optionssought. Biological effects monitoring at different scales both within macro- and meiofaunal groups is seenas a tool to aid the effective management of this TBT-contaminated dredged material.ReferencesChamp, M. A., and Seligman, P. F. (1996). “Organotin: Environmental fate and effects,” Chapman andHall, London, UK.Gibbs, P. E., Bryan, G. W., Pascoe, P. L., and Burt, G. R. (1987). “The use of the dogwhelk, Nucellalapillus, as an indicator of Tributyltin (TBT) contamination,” Journal of the Marine BiologicalAssociation, UK, 67, 507-523.Great Britain-Parliament. (1985). “Food and environment protection act, 1985,” Chapter 48, Her Majesty’sStationery Office , London.International Council for the Exploration of the Sea (ICES). (2002a). “Biological effects of contaminants:Sediment bioassay using the polychaete Arenicola marina,” ICES CIEM, No. 29, 17.International Council for the Exploration of the Sea (ICES). (2002b). “Biological effects of contaminants:Corophium sp. sediment bioassay and toxicity test,” ICES CIEM No. 28, 20.Matthiessen, P., and Gibbs, P. E. (1998). “Critical appraisal of the evidence for tributyltin-mediatedendocrine disruption in molluscs,” Environmental Toxicology and Chemistry 17(1), 37-43.Oehlmann, J., Stroben, E., and Fioroni, P. (1991). “The morphological expression of imposex in thedogwhelk, Nucella lapillus (Linnaeus) (Gastropoda: Muricidae),” Journal of Molluscan Studies, 57,375-390.77

Reed, J., Waldock, M. J., Jones, B., Blake, S. J., Roberts, P., Jones, G., Elverson, C., Hall, S., andMurray, L. A. (2002). “Remediation techniques applied to reduce paint-derived TBT in dredgedmaterial,” Proceedings of the Remediation of Contaminated Sediments, Venice, Italy, 10-12 October,2001.Rees, H. L., Waldock, R., Mattheissen, P., and Pendle, M. A. (1999). “Surveys of the epibenthos of theCrouch estuary (UK) in relation to TBT contamination,” J. Mar. Biol. Assoc. U.K., 79, 209-233.Rees, H. L., Waldock, R., Matthiessen, P., and Pendle, M. A. (2001). “Improvements in the epifauna ofthe Crouch estuary (United Kingdom) following a decline in TBT concentrations,” Mar. Pollut. Bull.,42, 137-144.Schratzberger, M., Wall, C., Reynolds, W., Reed, J., and Waldock, M. (2002). “Effects of paint-derivedtributyltin on structure of estuarine nematode assemblages in experimental microcosms,” J. Exp. Mar.Biol. Ecol., 272, 217-35.Smith, A. J., Thain, J. E., and Barry, J. (2005). “Exploring the use of caged Nucella lapillus to monitorchanges to TBT hotspot areas: A trial in the River Tyne estuary (UK).”Valkirs, A. O., and Stallard, M. D. (1987). “Butyltin partitioning in marine waters,” Proceedings ofOCEANS '87, IEEE Ocean Engineering Society, Piscataway, NJ.Waldock, M. J., and Thain, J. E. (1983). “Shell thickening in Crassostrea gigas: Organotin antifouling orsediment induced?,” Marine Pollution Bulletin 14 (10), 411-415.78