Ecological Evaluation Technical Guidance - State of New Jersey

elatively sedentary organisms that inhabit or depend upon the sedimentenvironment for their various life functions. They are sensitive to both longtermand short-term changes in sediment and water quality and are frequentlyused as environmental indicators of biological integrity because they arefound in most aquatic habitats, are of a size permitting ease of collection, canbe used to describe water-quality conditions or health of ecosystemcomponents, and can identify causes of impaired conditions (USEPA, 1990a).Benthic macroinvertebrate surveys are advantageous in that they integrate theinteractions of multiple contaminants and multiple routes of exposure, and canrespond to a broad array of potential pollutants. Some limitations are that theydo not identify the contaminant responsible for the observed toxicity,population impacts are not readily translated into contaminant remediationgoals, and results are often confounded by variables not related to contaminanttoxicity (predation, seasonal differences, physicochemical sedimentcharacteristics, food availability).The utility of benthic macroinvertebrate surveys may diminish whenconducted in urban streams and rivers that are known to contain diffuseanthropogenic pollutants and/or multiple industrial point discharges. Underthese conditions, survey results often indicate the presence of pollutiontolerant organisms with little to no difference in diversity when compared tothe results from a reference area location, and offer limited useful informationregarding impacts that can be attributed directly to the site under investigation.Under these circumstances, the investigator may decide to rely more heavilyon other lines of evidence such as sediment toxicity tests and receptor tissueconcentrations.A full description of how to conduct a benthic macroinvertebrate survey isbeyond the scope of this document; however, some of the more commonlyused references are provided in Section 11.0 (USEPA, 1999b; USEPA, 1990a;USEPA, 1998b; and Long and Chapman, 1985).6.2.2.3 Sediment Pore Water SamplingBulk sediment chemistry data are derived from measuring only the solid phaseof a sediment sample via standard analytical methods. Typically, bulksediment chemistry data are compared to conservatively based screeningcriteria to evaluate potential risk to benthic infauna. This type of comparisonis generally conducted during the screening phase of an investigation and it isacknowledged that site-specific bioavailability is not being measured at thisstage.In addition to direct exposure to contaminants associated with the sedimentsolid phase (e.g. mineral or organic phases), benthic organisms are exposed tothe sediment pore water, which is the water located in the interstitial spacebetween the sediment solid-phase particles. It is widely recognized thatcontaminant pore water concentrations more accurately predict toxicity andobserved community level effects than do whole sediment concentrations fornonionic compounds (Di Toro et al., 1991, 2005a; Di Toro, 2008; Hansen etEcological Evaluation Technical Guidance Document 58Version 1.2 8/29/12