Classification tools for marine ecological quality assessment ... - ecasa

Classification tools for marine ecological quality assessment ... - ecasa

ICES CM 2003/Session J-02CLASSIFICATION TOOLS FOR MARINE ECOLOGICAL QUALITYASSESSMENT: THE USEFULNESS OF MACROBENTHICCOMMUNITIES IN AN AREA AFFECTED BY A SUBMARINEOUTFALLAbstractÁngel Borja, J. Franco and I. MuxikaAZTI FoundationDepartment of Oceanography and Marine EnvironmentHerrera Kaia, Portualdea, z/g20110 – Pasaia (Spain)Tel: +34-943-004800; fax: +34-943-004801e-mail: aborja@pas.azti.esIn December 2000, the Water Framework Directive (WFD) entered into force. TheWFD establishes that the ecological status of water masses must be assessed. In order toundertake this requirements, several biological elements must be considered; amongst others,benthic invertebrates. To comply with the requirements of the WFD, some classificationtools for biological elements have been developed within Europe. Benthicmacroinvertebrates are the most traditionally used biological indicators of ecosystem healthin the marine environment. AZTI has developed a tool (AMBI:, which providesassistance in determining the impacts and quality status of soft-bottom marine benthiccommunities; it is being utilised broadly along European coasts. In this communication,different metrics for benthic macroinvertebrates in coastal areas are compared, including theAMBI, richness, diversity, biomass and abundance. They are also combined in a biologicalquality index. Such comparison is undertaken by considering the results obtained from amonitoring programme in a coastal area affected by a submarine outfall, on the Basque coast(N. Spain). The investigation includes several surveys undertaken before and after theconstruction of the outfall. These results will be discussed within the framework of the WFDrequirements.Keywords: biotic coefficient, impact evaluation, soft-bottom benthos, WaterFramework Directive, submarine outfallIntroductionThe European Water Framework Directive (WFD 2000/60/EC) develops the concept ofEcological Quality Status (EQS) for the assessment of the quality of water masses and, by2006, European Member States will be required to establish ecological quality objectives.The assessment of the status will be based upon the composition and abundance of differentbiological elements of the ecosystem (e.g. phytoplankton, benthos, fish), as well as the

BORJA, FRANCO AND MUXIKAphysico-chemical and hydromorphological indicators in relation to reference sites. The WFDsets the objective to prevent deterioration in the status of all Community waters (i.e. bothsurface- and ground-waters, including coastal waters, throughout the EU) and to ensure theachievement of their good status by 2015.Similarly, other international initiatives and agreements are following the sameobjectives. The Oslo & Paris Convention (1992) has promoted and is in the process ofadopting Ecological Quality Objectives (EQO), for the implementation of its strategies tocombat eutrophication and for the promotion of an ecosystem approach to environmentalassessment. The European Environment Agency has been advocating the development ofindicators of change and, on a larger scale, the Earth Summits at Rio de Janeiro (1992) andJohannesburg (2002) require quantitative indicators as a tool in the modelling, monitoringand management of aquatic systems. For the marine environment, it is well accepted thatsome biological components are more valuable than others as integrative environmentalindicators and the WFD places a significant emphasis on sedentary benthic communitiesinhabiting the beds of estuaries and coastal areas.Ecologically-based classification schemes for the WFD will be based upon five classes(High, Good, Moderate, Poor and Bad), with the main aim being to achieve at least ‘good’ecological status for all water bodies. According to the WFD, the surface water bodies areclassified in rivers, lakes, transitional waters or coastal waters (apart from artificial andheavily modified surface water bodies). Likewise, the application of the WFD to transitionaland coastal waters requires a significant amount of effort, to ensure effective implementation,as outlined by the CIS Working Group 2.4 (Coast) created by the Common ImplementationStrategy.Further to their central role in marine ecosystem functioning, the benthic invertebratesare a well-established target in evaluations of environmental quality status. Various studieshave demonstrated that the macrobenthos responds relatively rapidly to anthropogenic andnatural stress (Pearson and Rosenberg, 1978; Dauer, 1993) and macrobenthic animals: (i) arerelatively sedentary i.e. cannot avoid deteriorating water/sediment quality conditions; (ii)have relatively long life-spans (thus, indicate and integrate water/sediment quality conditions,over time); (iii) consist of different species that exhibit different tolerances to stress; and (iv)have an important role in cycling nutrients and materials, between the underlying sedimentsand the overlying water column (Hily, 1984; Dauer, 1993). Several authors have reviewedthe use of biotic indices (Washington, 1984; Codling and Ashley, 1992). Many authors (e.g.Washington, 1984) accept that a biotic index is unlikely to be universally applicable, asorganisms are not equally sensitive to all types of anthropogenic disturbance and are likely torespond differently to different types of perturbation. As such, they may provide a way toestablish a multimetric bioassessment method that can be modified for different geographicalregions. Several indices have been proposed for use in estuarine and coastal waters; some ofthese attempt to include the five-step environmental model of the WFD (Rumohr et al.,1996). Some authors have made attempts to use these tools as a proxy of the impact at sea(Hily, 1984; Rygg, 1985; Majeed, 1987; Dauer, 1993; Engle et al., 1994; Grall andGlémarec, 1997; Weisberg et al., 1997; Roberts et al., 1998; Borja et al., 2000, 2003; Eaton,2001; Simboura and Zenetos, 2002). Moreover, these approaches are based upon differentpremises and do not address all of them directly in the establishment of the EQS, for thewhole of Europe, sensu the WFD.2

CLASSIFICATION TOOLS FOR MARINE ECOLOGICAL QUALITY ASSESSMENTIn this case, the use of the diversity and abundance of macroinvertebrate taxa, togetherwith the presence of disturbance-sensitive taxa and taxa indicative of pollution (bioticindices), are proposed to be measured as useful metrics in determining the ecological status.However, at present, the abovementioned tools do not fulfil all the requirements proposed inthe WFD. A recent guidance document, written by the group implementing the WFD,declares that “methods combining composition, abundance and sensitivity may be the mostpromising” (Vincent et al., 2002).Borja et al. (2000) proposed a Marine Biotic Index (AMBI) to establish the ecologicalquality of soft-bottom benthos within European estuarine and coastal environments. Such anindex, based upon the sensitivity/tolerance of benthic fauna to stress gradients, classifies thespecies into five ecological groups. The distribution of these ecological groups provides abiotic index of 5 levels of pollution classification, as in the WFD (Table 1). The index hasbeen validated and applied to different impact sources and geographical areas (Borja et al.,2000, 2003), demonstrating its usefulness.Table 1. Summary of the AMBI values and their equivalences (after Borja et al., 2000). The last column showsthe proposed equivalent Ecological Status (WFD), as used in this study.DominatingSite Pollution EcologicalAMBI valueBenthic Community HealthEcological Group Classification Status0.0 < BC ≤ 0.2 I NormalUnpolluted High Status0.2 < BC ≤ 1.2 Impoverished1.2 < BC ≤ 3.3 III Unbalanced Slightly Polluted Good Status3.3 < BC ≤ 4.3 Transitional to pollution Moderate StatusMeanly Polluted4.3 < BC ≤ 5.0 IV-V PollutedPoor Status5.0 < BC ≤ 5.5 Transitional to heavy pollutionHeavily Polluted5.5 < BC ≤ 6.0 V Heavily pollutedBad StatusAzoic (7.0) Azoic Azoic Extremely PollutedIn this study, the possible incorporation of new metrics to the AMBI will be explored,following the requirements of the WFD. The data provided by the monitoring ofmacrobenthic communities in an area affected by a submarine outfall in San Sebastian(Basque Country, North of Spain) (Figure 1), will be used as a case study.MethodologyThe biotic indexAn extense presentation of the index development and its application has beendescribed in Borja et al. (2000). The updated species list, with more than 2,000 taxa from allEuropean seas, including their assignment to the ecological groups, together with theAMBI© 2.0 program (AZTI’ Marine Biotic Index) to calculate and represent the index, areavailable (free of charge) in AZTI’s web page ( The list and the program arebeing continuously updated.The case studyIn the spring of 2001, as a transitory solution until complete cleaning of the waterwithin the context of the sewerage scheme, the initial discharges (old outfall) from the SanSebastian and Pasaia area (north of Spain), were diverted to a submarine outfall. This outfall3

BORJA, FRANCO AND MUXIKAis located 1.2 km from the coast in an approx. 47 m water depth (Figure 1a).(a)(b)Figure 1. (a) Location of the case study area, in the north of Spain, showing the position of the old outfall andthe new submarine outfall, and (b) the sampling stations over the area.The benthic communities were studied 5 months before the diversion, and 4 and 16months after the diversion. Benthos was sampled with a box-corer grab, at 9 samplingstations (Figure 1b); 3 replicates were taken at each sampling site. All of the samples weresorted out, identified, and counted. Benthic communities at two separate stations (sampledbefore the diversion, in areas of 50 and 160 m water depth, some 5 miles apart, not shown inFigure 1) were used, as a proxy to reference conditions over the region (data from Martínezand Adarraga, 2001).Here, data have been used on species richness (number of species), abundance (asnumber of individuals, per square metre), Shannon’s diversity (based upon abundance), andAMBI (calculated as mentioned above).Incorporating new metricsThe metrics used, in order to accomplish the requirements of the WFD, require thatthe final value must range between 0 (bad ecological quality) and 1 (high ecological quality),with 5 levels of quality. In this study, it is proposed to combine three different metrics:diversity, richness and the biotic coefficient (AMBI), following the criteria listed in Table 2.These metrics provide a value which is a rate between the value obtained and that of thereference site (in this particular case, taking as reference those values equivalent to anEcological Quality Ratio (EQR) of 1). For each of the metric values there is an EquivalentAssigned Value (EAV, in Table 2). The EQR is calculated as the mean of the EAVs for eachstation. Then, each EQR has an associated ecological status.4

CLASSIFICATION TOOLS FOR MARINE ECOLOGICAL QUALITY ASSESSMENTTable 2. Calculating the Ecological Quality Ratio (EQR), with diversity, richness and AMBI, together with theequivalence in terms of the ecological status (WFD). EAV: Equivalent Assigned Value.Diversity Richness AMBI EAV EQR Ecological Status0-1.2 0-15 5.5-7 0 0-0.25 Bad1.2-2.4 15-30 4.3-5.5 0.25 0.25-0.5 Poor2.4-3.6 30-45 3.3-4.3 0.5 0.5-0.7 Moderate3.6-4.8 45-60 1.2-3.3 0.75 0.7-0.9 Good>4.8 >60 0-1.2 1 0.9-1 HighResults and DiscussionFigure 2 shows the main results obtained at each of the locations and for each of thesampling periods.Before the discharge diversion, the highest richness (> 70 species) is observed at thereference stations (R-50 and R-160) (Figure 2a); the lowest value (11 species) is reached nearthe old outfall (COAST) and in the immediate surroundings; these are more affected bypollution. After diversion, there is a progressive improvement in the richness values near theold outfall (approaching 40 species after 16 months). However, the new submarine outfall,together with those to the south (stations OUTFALL, S1 and S2), experiences somedeterioration in richness, after the diversion. No clear trends are observed in the stationsnorthwards to the submarine outfall.Before diversion, the reference stations, with those situated far to the north from theold outfall, present the lowest abundances (Figure 2b). The most affected station (COAST)show high abundance values (> 5,000 ind.m -2 ), due to the presence of very abundant smallopportunistic species (such as Capitella capitata or Malacoceros fuliginosus, which representmore than 95% of the total abundance). After the diversion, this station experienced animmediate increase in abundance, followed by a decrease; this was due to the new conditionsi.e. the absence of organic inputs to the system. On the other hand, the abundancedramatically increased in the newly affected stations, with values > 4,000 ind.m -2 .Before the diversion, the highest diversities (between 3.5 and 5.7 bit.ind -1 ) were foundat the reference stations and the non-affected stations (Figure 2c). After the dischargediversion, the old outfall station (COAST) improves significantly its diversity, from 4values. The area near the new outfall reaches values around 1 bit.ind -1 . On another occasion,the most affected area, in terms of diversity, is that situated to the south of the new impactsource point (OUTFALL); changes to the north are indistinguishable.The same pattern can be seen in relation to the Biotic Coefficient (Figure 2d). Thereference and the non-affected stations present low biotic coefficients (unpolluted or slightlypolluted (following the terminology of Borja et al., 2000, see also Table 1)) before thediversion. For contrast, the stations more affected by the discharges present high bioticcoefficients (heavily polluted). Following the diversion, there is an improvement in terms ofthis index at the COAST station, but the area around the new discharge is of poor quality. Ingeneral, well-marked gradients, both spatial (Figure 3) and temporal (Figures 2d and 3), canbe detected by means of the Biotic Coefficient.5

BORJA, FRANCO AND MUXIKARichness (n sp.)Abundance (n.m -2 )Shannon DiversityBiotic Coefficient9080706050403020100100008000600040002000065432106543210(a)(b)(c)(d)COAST S2 SW SE S1 OUTFALLNW NE N R-50 R-160Figure 2. Evolution of several structural parameters at the studied locations: (a) taxonomic richness; (b)abundance; (c) Shannon diversity; and (d) biotic coefficient (AMBI). Key: black columns show data 5 monthsbefore the discharge diversion from the old outfall (COAST), to the new submarine outfall (OUTFALL); greycolumns show data 4 months after diversion; and white columns 16 months after diversion.6

CLASSIFICATION TOOLS FOR MARINE ECOLOGICAL QUALITY ASSESSMENT1. AFTER-1 AFTER-2Figure 3. The Biotic Coefficient values (AMBI), both in spatial and temporal perspective.In studying the different relationships between the biological indicator metrics usedhere (Figure 4), the Biotic Coefficient is related negatively with diversity and richness and isrelated positively with abundance. Further, abundance is related negatively with richness anddiversity and, finally, richness and diversity are positively related. This pattern indicates, atleast in this particular case study, that there exist close relationships between the metricsproposed by the WFD for the determination of the ecological status.Taking into account the small discriminatory effect of the abundance, in terms ofdetecting the impact of pollution on communities (see data in Figure 2b), those structuralparameters helping in the determination of such an impact have been used in this study.These are, as described in the methodology, diversity, richness and biotic index.In this way, when calculating the EQS for the different sampling stations, before andafter diversion and based upon the methodology shown in Table 2, the results are verycomprehensible under the terms of the WFD (Figure 4). Hence, the area near the old outfall(COAST), improves in its quality, from a ‘bad’ ecological status to a ‘moderate’ status, after14 months of the discharge diversion. In the case of the new submarine outfall (OUTFALL),together with the surrounding affected area (S1, S2), the opposite situation occurs: from a‘moderate’ or ‘good’ status, the area changes to a ‘poor’ or ‘bad’ status. Sampling areas usedas reference, or areas to the north of the new outfall (out of the main tidal current direction),remain with ‘high’ or ‘good’ ecological status. Finally, other areas are less affected by thedischarges (SW, SE), but change their status over time, with a small worsening in theirquality.An interesting point to note is that the deterioration of the benthic communities in thearea affected by the new discharges is much faster (less than six months) than the recovery ofthe communities in the areas positively affected by the waste elimination (more than oneyear).The results obtained here suggest that the combined use of biotic indices (such asAMBI), in combination with other structural parameters of the community (such as richnessand diversity), could be useful in determining the ecological status of the Europeantransitional and coastal waters. Furthermore, this approach can accomplish all therequirements of the WFD (using diversity and richness, together with the presence ofdisturbance-sensitive taxa and taxa indicative of pollution or biotic indices).7

BORJA, FRANCO AND MUXIKA76RICHNESS - BC*5432100 20 40 60 80 100654321RICHNESS - DIVERSITY**065432100 20 40 60 80 100ABUNDANCE (x1000) - DIVERSITY**0 2 4 6 8 10108RICHNESS - ABUNDANCE (x1000)*64200 20 40 60 80 1007654321ABUNDANCE (x1000) - BC**0765432100 2 4 6 8 10DIVERSITY - BC**0 1 2 3 4 5 6Figure 4. Relationships between the different biological indicator metrics. Statistically significant correlationsare indicated by * (p

CLASSIFICATION TOOLS FOR MARINE ECOLOGICAL QUALITY ASSESSMENTConclusionsThe taxonomic richness, the diversity and the biotic coefficient follow a linearrelationship with the degree of affection by the discharges. Likewise, the abundance shows amore complex relationship to the degree of influence.The metrics proposed and used in this study are able to differentiate non-affectedfrom affected sites, to detect human impacts and to establish temporal and spatial changes.These metrics can be combined, in order to provide a general index of ecologicalquality, measuring the ecological status, as established by the WFD.AcknowledgementsThis work was supported by funds provided by the Departamento de ObrasHidraúlicas, de la Diputación Foral de Gipuzkoa and Aguas del Añarbe. Moreover, theSociedad Cultural Insub identified the species in the samples. Finally, Prof. Michael Collins(SOES, Southampton Oceanography Centre), kindly revised an early version of the draft.ReferencesBorja, Á., J. Franco, and V. Pérez, 2000. A Marine Biotic Index to Establish the EcologicalQuality of Soft-Bottom Benthos within European Estuarine and Coastal Environments.Marine Pollution Bulletin, 40: 1100-1114.Borja, Á., I. Muxika and J. Franco, 2003. The application of a Marine Biotic Index todifferent impact sources affecting soft-bottom benthic communities along Europeancoasts. Marine Pollution Bulletin, 46: 835-845.Codling, I..D. and S.J. Ashley, 1992. Development of a biotic index for the assessment ofpollution status of marine benthic communities. Final report to SNIFFER and NRA.NR 3102/1.Dauer, D.M., 1993. Biological criteria, environmental health and estuarine macrobenthiccommunity structure. Marine Pollution Bulletin, 26(5): 249-257.Eaton, L., 2001. Development and validation of biocriteria using benthic macroinvertebratesfor North Carolina estuarine waters. Marine Pollution Bulletin, 42: 23-30.Engle, V.D., J.K. Summers and G.R. Gaston, 1994. A benthic index of environmentalcondition of Gulf of Mexico estuaries. Estuaries, 17: 372-384.Grall, J. and M. Glémarec, 1997. Using biotic indices to estimate macrobenthic communityperturbations in the Bay of Brest. Estuarine, Coastal and Shelf Science, 44(sup. A): 43-53.Hily, C., 1984. Variabilité de la macrofaune benthique dans les milieux hypertrophiques dela Rade de Brest. Thèse de Doctorat d’Etat, Univ. Bretagne Occidentale. Vol. 1: 359pp., Vol. 2: 337 pp.Majeed, S.A., 1987. Organic matter and biotic indices on the beaches of North Brittany.Marine Pollution Bulletin, 18(9): 490-495.9

BORJA, FRANCO AND MUXIKAMartínez, J. and I. Adarraga, 2001. Distribución batimétrica de comunidadesmacrobentónicas de sustrato blando en la plataforma continental de Guipúzcoa (golfode Vizcaya). Boletín del Instituto Español de Oceanografía, 17(1 y 2): 33-48.Pearson, T. and R. Rosenberg, 1978. Macrobenthic succession in relation to organicenrichment and pollution of the marine environment. Oceanography and MarineBiology Annual Review, 16: 229-311.Roberts, R.D., M.R. Gregory and B.A. Fosters, 1998. Developing an efficient macrofaunamonitoring index from an impact study – A dredge spoil example. Marine PollutionBulletin, 36(3) : 231-235.Rygg, B., 1985. Distribution of species along pollution-induced diversity gradients in benthiccommunities in Norwegian fjords. Marine Pollution Bulletin, 16 (12): 469-474.Simboura, N. and A. Zenetos, 2002. Benthic indicators to use in Ecological QualityClassification of Mediterranean soft bottom marine ecosystems, including a new BioticIndex. Mediterranean Marine Science, 3/2: 77-111.Vincent, C., H. Heinrich, A. Edwards, K. Nygaard, and J. Haythornthwaite, 2002. Guidanceon typology, reference conditions and classification systems for transitional andcoastal waters. Produced by: CIS Working Group 2.4 (Coast), CommonImplementation Strategy of the Water Framework Directive, European Commission,119 pp.Washington, H.G., 1984. Diversity, biotic and similarity indices. A review with specialrelevance to aquatic ecosystems. Water Research, 18: 653-694.Weisberg, S.B., J.A. Ranasinghe, D.M. Dauer, L.C. Schaffner, R.J. Diaz and J.B. Frithsen,1997. An estuarine benthic index of biotic integrity (B-IBI) for Chesapeake Bay.Estuaries, 20(1): 149-158.10

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