CHAPTER Application of Ecological Indicators to Assess Environmental Quality in Coastal Zones and Transitional Waters: Two Case Studies J.C Marques, F Salas, J.M Patrı´ cio, and M.A Pardal This chapter addresses the application of ecological indicators in assessing the biological integrity and environmental quality in coastal ecosystems and transitional waters In this context, the question of what might be considered a good ecological indicator is approached, and the different types of data most often utilized to perform estimations are discussed Moreover, we present a brief review on the application of ecological indicators in coastal and transitional waters ecosystems referring to: (1) indicators based on species presence vs absence; (2) biodiversity as reflected in diversity measures; (3) indicators based on ecological strategies; (4) indicators based on species biomass and abundance; (5) indicators accounting for the whole environmental information; and (6) thermodynamically oriented and network analysis-based indicators Algorithms are provided in an abridged way and the pros and cons regarding the application of each indicator are discussed The question of how to choose the most adequate indicator for each particular case is discussed as a function of data requirements and data availability Two case studies are used to illustrate whether a number of selected ecological indicators were satisfactory in describing the state of ecosystems, comparing their relative performances and Copyright © 2005 by Taylor & Francis 68 HANDBOOK OF ECOLOGICAL INDICATORS FOR ASSESSMENT OF ECOSYSTEM HEALTH discussing how their usage can be improved for environment health assessment The possible relation between values of these indicators and the environmental quality status of ecosystems was analyzed We reached the conclusion that to select an ecological indicator, we must account for its dependence on external factors beyond our control, such as the need for reference values that often not exist, or particular characteristics regarding the habitat type As a result, it is reasonable to say that no indicator will be valid in all situations, and that a single approach does not seem appropriate due to the complexity inherent in assessing the environmental quality status of a system Therefore, as a principle, such evaluation should be always performed using several ecological indicators, which may provide complementary information 3.1 INTRODUCTION Ecological indicators are commonly used to supply synoptic information about the state of ecosystems They usually address an ecosystem’s structure and/or functioning accounting for a certain aspect or component; for example, nutrient concentrations, water flows, macroinvertebrates and/or vertebrates diversity, plants diversity, plants productivity, erosion symptoms, and sometimes ecological integrity at a systems level The main attribute of an ecological indicator is to combine numerous environmental factors in a single value, which might be useful in terms of management and for making ecological concepts compliant with the general public understanding Moreover, ecological indicators may help in establishing a useful connection between empirical research and modeling since some of them are of use as orientors (also referred to in the literature as goal functions) in ecological models Such application proceeds from the fact that conventional models of aquatic ecosystems are not effective in predicting the occurrence of qualitative changes in ecosystems; for example, shifts in species composition, which is due to the fact that measurements typically carried out — such as biomass and production — are not efficient at capturing such modifications (Nielsen, 1995) Nevertheless, it has been tried to incorporate this type of changes in structurally dynamic models (Jørgensen, 1992; Nielsen, 1992, 1994, 1995; Jørgensen et al., 2002), to improve their predictive capability, achieving a better understanding of ecosystem behavior, and consequently a better environmental management In structurally dynamic models, the simulated ecosystem behavior and development (Nielsen, 1995; Strasˇ kraba, 1983) is guided through an optimization process by changing the model parameters in accordance with a given ecological indicator, used as an orientor (goal function) In other words, this allows the introduction in models parameters that change as a function of changing forcing functions and conditions of state variables, optimizing the model outputs by a stepwise approach In this case, the orientor is assumed to express a given macroscopic property of the ecosystem, resulting from the emergence of new characteristics arising from self-organization processes Copyright © 2005 by Taylor & Francis In general, the application of ecological indicators is not free from criticism One such criticism is that aggregation results in oversimplification of the ecosystem under observation Moreover, problems arise from the fact that indicators account not only for numerous specific system characteristics, but also other kinds of factors; for example, physical, biological, ecological, socioeconomic etc Indicators must therefore be utilized following the right criteria and in situations that are consistent with its intended use and scope; otherwise they may lead to confusing data interpretations This paper addresses the application of ecological indicators for assessing the biological integrity and environmental quality in coastal ecosystems and transitional waters The possible characteristics of a good ecological indicator, or what kind of information regarding ecosystem responses can be obtained from the different types of biological data usually taken into account in evaluating the state of coastal areas, has already been discussed in chapter Two cases studies are used to illustrate whether different types of indicators were satisfactory in describing the state of ecosystems, comparing their relative performances and discussing how can their usage be improved for environment health assessment 3.2 BRIEF REVIEW ON THE APPLICATION OF ECOLOGICAL INDICATORS IN ECOSYSTEMS OF COASTAL AND TRANSITIONAL WATERS Almost all coastal marine and transitional waters ecosystems all over the world have been under severe environmental stress following the settlement of human activities Estuaries, for example, are the transition between marine, freshwater and land ecosystems, being characterized by distinctive biological communities with specific ecological and physiological adaptations In fact, we may say that the estuarine habitat does not imply a simple overlap of marine and land factors, constituting instead an individualized whole with its own biogeochemical factors and cycles, which represents the environment for real estuarine species to evolve In such ecosystems, besides resources available, fluctuating conditions, namely salinity and type of substrate, are a key issue regarding an organism’s ecological distribution and adaptive strategies (see, for example, McLusky, 1989; Engle et al., 1994) The most common types of problems in terms of pollution include illegal sewage discharges associated with nutrient enrichment; pollution due to toxic substances such as pesticides, heavy metals, and hydrocarbons; unlimited development; and habitat fragmentation or destruction In the case of transitional waters, limited water circulation and inappropriate water management tends to concentrate nutrients and pollutants, and to a certain extent we may say that sea pollution begins there (Perillo et al., 2001) Moreover, in estuaries, drainage of harbors and channels modifies geomorphology, water circulation, and other physicochemical features, and consequently the habitat’s characteristics In recent times, perhaps the most Copyright © 2005 by Taylor & Francis important problem is the excessive loading of nutrients mainly due to fertilizers used in agriculture, and untreated sewage water, which induces eutrophication processes These problems can be observed all over the world Many ecological indicators used or tested in evaluating the status of these ecosystems can be found in the literature, resulting from just a few distinct theoretical approaches A number of them focus on the presence or absence of given indicator species, while others take into account the different ecological strategies carried out by organisms, diversity, or the energy variation in the system through changes in the biomass of individuals A last group of ecological indicators are thermodynamically oriented or based on network analysis, and look for capturing the information on the ecosystem from a more holistic perspective (Table 3.1) 3.2.1 Indicators Based on Species Presence vs Absence Determining the presence or absence of one species or group of species has been one of the most used approaches in detecting pollution effects For instance, the Bellan, (based on polychaetes), or the Bellan–Santini (based on amphipods) indices attempt to characterize environmental conditions by analyzing the dominance of species that indicate some type of pollution in relation to the species considered to indicate an optimal environmental situation (Bellan, 1980; Bellan and Santini, 1980) Several authors not advise the use of these indicators because often such indicator species may occur naturally in relative high densities The point is that there is no reliable methodology to know at which level the indicator species can be well represented in a community that is not really affected by any kind of pollution, which leads to a significant exercise of subjectivity (Warwick, 1993) Despite these criticisms, even recently, the AMBI index (Borja et al., 2000), which is based on the Glemarec and Hily (1981) species classification regarding pollution; as well as the Bentix index (Simbora and Zenetos, 2002), have gone back to update such pollution detecting tools Roberts et al (1998) also proposed an index based on macrofauna species, which accounts for the ratio of each species abundance in control vs samples proceeding from stressed areas It is however semiquantitative as well as site- and pollution type-specific The AMBI index, for example, accounts for the presence of species indicating a type of pollution and of species indicating a reference situation assumed to be polluted It has been considered useful in terms of the application of the European Water Framework Directive in coastal ecosystems and estuaries In fact, although this index is very much based on the paradigm of Pearson and Rosenberg (1978), which emphasizes the influence of organic matter enrichment on benthic communities, it was shown to be useful in assessing other anthropogenic impacts, such as physical alterations in the habitat, heavy metal inputs, etc in several European areas of the Atlantic (North Sea; Bay of Biscay; and southern Spain) and Mediterranean coasts (Spain and Greece) (Borja et al., 2003) Copyright © 2005 by Taylor & Francis Table 3.1 Short review of environmental quality indicators regarding the benthic communities Type of indicator Based on species presence vs absence Requirements and applicability evaluation List of species Subjective in most of the cases Only the use of AMBI and Bentix is recommended Algorithm Bellan index (Bellan, 1980): X pollution species indicator IP ¼ no pollution species indicator Pollution indicator species: Platenereis dumerilli, Theosthema oerstedi, Cirratulus cirratus and Dodecaria concharum No-pollution indicator species: Syllis gracillis, Typosyllis prolifera, Typosyllis sp and Amphiglena mediterranea Bellan–Santini index (Bellan-Santini,1980): X pollution species indicator IP ¼ no pollution species indicator Pollution indicator species: Caprella acutrifans and Podocerus variegates No-pollution indicator species: Hyale sp, Elasmus pocillamunus and Caprella liparotensis AMBI (Borja et al., 2000): È %GIị ỵ 1:5 %GIIị ỵ %GIIIị ỵ 4:5 %GIVị ỵ %GVịg AMBI ¼ 100 GI: Species very sensitive to organic enrichment and present under unpolluted conditions GII: Species indifferent to enrichment GIII: Species tolerant to excess of organic matter enrichment GIV: Second-order opportunist species, mainly small sized Polychaetes GV: First-order opportunist species, essentially deposit-feeders Bentix (Simboura and Zenetos, 2002) : È É %GIị ỵ %GII ỵ %GIIIị Bentix ¼ 100 GI: Species very sensitive to pollution GII: Species tolerant to pollution GIII: Second-order and first-order opportunist species (Continued ) Copyright © 2005 by Taylor & Francis Table 3.1 Continued Type of indicator Requirements and applicability evaluation Algorithm Based on ecological strategies List of taxa (species or higher taxonomic groups) and knowledge on their life strategies, which can be in the literature Subjective Not recommended Nematodes/copepods ratio (Rafaelli and Mason, 1981): nematodes abundance I¼ copepodes abundance ´ Polychaetes/amphipods ratio (Gomez Gesteira, 2000): Polychaetes abundance ỵ1 Log10 Amphipodes abundance Infaunal index (Word, 1979): ITI ¼ 100 À 100/3 (0n1 ỵ 1n2 ỵ 2n3 ỵ 3n4)/(n1 ỵ n2 þ n3 þ n4) n1 ¼ number of individuals of suspensivores feeders n2 ¼ number of individuals of interface feeders n3 ¼ number of individuals of surface deposit feeders n4 ¼ number of individuals of subsurface deposit feeders Diversity measures Quantitative samples; adequate taxa identification; Data on species density (number of individuals and/or biomass) In the case of K-dominance curves, time series for the same local are desirable Although not exempt from subjectivity, results might be useful Shannon–Wienner index (Shannon–Wienner, 1963): P pi log2 pi H0 ¼ Where pi is the proportion of abundance of species i in a community were species proportions are p1, p2, p3 pn Copyright © 2005 by Taylor & Francis Margalef index: D ¼ (S À 1)/logeN Where S is the number of species found and N is the total number of individuals Berger-Parker index: D ¼ (nmax)/N Where nmax is the number of individuals of the dominant species and N is the total number of individuals Simpson index: P D ¼ ni(ni À 1)/N(N À 1) Where ni is the number of individuals of species i and N is the total number of individuals Average taxonomic diversity index (Warwick and Clarke, 1995 1998): PP Á¼[ i