Assessing ecological integrity in marine waters, using multiple indices and ecosystem components: Challenges for the future (original) (raw)
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Marine Pollution Bulletin, 2008
In recent years, several sets of legislation worldwide (Oceans Act in USA, Australia or Canada; Water Framework Directive or Marine Strategy in Europe, National Water Act in South Africa, etc.) have been developed in order to address ecological quality or integrity, within estuarine and coastal systems. Most such legislation seeks to define quality in an integrative way, by using several biological elements, together with physico-chemical and pollution elements. Such an approach allows assessment of ecological status at the ecosystem level ('ecosystem approach' or 'holistic approach' methodologies), rather than at species level (e.g. mussel biomonitoring or Mussel Watch) or just at chemical level (i.e. quality objectives) alone.
The need for validation of ecological indices
Ecological Indicators
Increased recognition of the need for ecosystem-based management has resulted in a growing body of research on the use of indicators to represent and track ecosystem status, particularly in marine environments. While multiple frameworks have been developed for selecting and evaluating indicators, certain types of indicators require additional consideration and validation. In particular, an index, which we define as an aggregation of two or more indicators, may have unique properties and behaviors that can make interpretation difficult, particularly in a management context. We assert that more rigorous validation and testing is required for indices, particularly those used to inform management decisions. To support this point we demonstrate the need for validation and then explore current development and validation processes for ecosystem indices. We also compare how other disciplines (e.g., medicine, economics) validate indices. Validating indices (and indicators) is particularly challenging because they are often developed without an explicit objective in mind. We suggest that exploring the sensitivity of an index to the assumptions made during its development be a prerequisite to employing such an index.
Ecological Indicators, 2013
In 1981, James R. Karr's paper 'Assessment of biotic integrity using fish communities' provided the first description of a multimetric procedure to assess the biotic integrity of aquatic ecosystems. To assess the contribution of the Index of Biotic Integrity (IBI) and ideas proposed by Karr for the management of aquatic ecosystems, we carried out a scientometric analysis of the papers published from 1981 to 2011 that cited Karr's study. The papers were obtained from Thomson Reuters' database (ISI Web of Knowledge) in October 2011. We used all papers that cited 'Karr, 1981' to assess temporal trends in citations and to identify which journals cited the index most frequently. A total of 93 papers were selected from the two journals that most frequently cited Karr's study, namely Hydrobiologia and Ecological Indicators. For each paper selected, we determined whether the study was empirical, theoretical, or methodological. For empirical papers we assessed the type of environment where the study was carried out, the indicator organisms used, and whether the IBI was applied. To identify which ideas suggested by Karr have been discussed in the literature, we assessed all papers found. In the time frame studied, 734 papers cited 'Karr, 1981'. The number of citations increased significantly with time. Most papers that cited 'Karr, 1981' were empirical, carried out in rivers and streams, and used fish as bioindicators. The main ideas discussed in these studies were related to the creation and use of the IBI, as well as to limitations and difficulties in its application. Our results suggest that the ideas proposed by Karr have contributed to the conservation of aquatic ecosystems. However, criteria for choosing different metrics, as well as the definition of reference conditions, are issues that need to be addressed in order to make the IBI a more robust index.
Frontiers in Marine Science
In the last decades, climate change and human pressures have increasingly and dramatically impacted the ocean worldwide, calling for urgent actions to safeguard coastal marine ecosystems. The European Commission, in particular, has set ambitious targets for member states with two major directives, the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD), both designed to protect the marine environment in EU waters. Diverse biotic indices have accordingly been developed to assess water and habitat quality. The WFD adopts four Biological Quality Elements (BQEs), whereas the MSFD recommends a set of eleven qualitative descriptors. The borderline between water quality and habitat quality is hard to trace and so far most assessments have involved the use of a few indices and were mainly related to a single BQE or qualitative descriptor. In this study, thanks to the availability of a large dataset encompassing a wide array of descriptors, we compared the perf...
2008
The assessment of ecological status of marine fish communities required by the marine strategy framework directive (MSFD) emphasises the need for fish-based ecological indices in marine waters. In this study we adapt five estuarine multimetric indices to the marine environment and apply them in three types of substrates, analysing the metrics responsible for the obtained patterns of ecological status. The results show inefficiency of the community degradation index (CDI) and the biological health index (BHI) in ecological status assessment and disagreement between the estuarine biotic integrity index (EBI), the estuarine fish community index (EFCI) and the transitional fish classification index (TFCI). Analysis of individual metrics suggests lack of representativeness and consideration for the particularities of each substrate’s typical fish communities. None of the tested indices were efficient on the marine environment, urging the need for new marine indices that account for differences between types of substrate and depth.
Development and Validation of an Estuarine Biotic Integrity Index
Estuaries, 1997
We tested hypotheses about how estuarine fish assemblages respond to habitat degradation and then integrated these responses into an overall index, the Estuarine Biotic Integrity Index (EBI), which smnmarized observed changes. Fish assemblages (based on trawl catches) and habitat quality were measured monthly or biweekly at nine sites in two estuaries from March 1988 to June 1990. Submerged aquatic vegetation habitats were classified as low or medium quality based on year-round measurements of chemical and physical characteristics (phytoplankton blooms; macroalgae; dissolved oxygen; nutrients; dredged channels). We tested 15 metrics and selected 8 for inclusion in the EBI: total number of species, dominance, fish abundance (number or biomass), number of nursery species, number of estuarine spawning species, number of resident species, proportion of benthlc-associated fishes, and proportion abnormal or diseased. Fish assemblages in low-quality sites had lower number of species, density, biomass, and dominance compared with mediumquality sites. Fish abundance peaked in July and August, and was lowest in January to March. The seasonal cycle in lowquality sites was damped compared with medium-quality sites. Abundances of fishes using estuaries as a spawning and nursery area and of benthic species were lower in low-quality sites compared to medium-quality sites. The individual metrics and the overall index correlate with habitat degradation. The EBI based on biomass did not do better than the EBI based on number, indicating that the extra effort to obtain biomass may not be warranted. We suggest the EBI is a useful indicator of estuarine ecosystem status because it reflects the relationship between anthropogenic alterations in estuarine ecosystems and the status of higher trophic levels.
The importance of setting targets and reference conditions in assessing marine ecosystem quality
Ecological Indicators, 2012
Assessing benthic quality status of marine and transitional water habitats requires to set up both: (i) tools (i.e. indices) to assess the relative quality of the considered habitat, and (ii) reference conditions for which such indices can be computed and used to infer the absolute ecological status (ES) of the considered habitat. The development of indices, their comparison and the assessment of the causes of their discrepancies have been largely discussed but less attention has been paid to the methods used for the setting of adequate reference conditions, although this step is clearly crucial for the sound assessment of ES. This contribution reviews the approaches available in setting both reference conditions (pristine areas, hindcasting, modelling and best professional judgment) and targets (baseline set in the past, current baseline and directional/trends). We scored the use of pristine or minimally impacted conditions as the best single method; however, the other methods were judged as adequate then combined with best professional judgment. The case of multivariate AMBI (AZTI's Marine Biotic Index) is used to highlight the importance of setting correct reference conditions. Hence, data from 29 references, including 14 countries from Europe and North America, and both coastal (15 cases) and transitional (17 cases) waters, have been used to study the response of multivariate AMBI to human pressures. Results show that the inability of this index to detect human pressure is in most cases linked with the use of inappropriate methods for setting reference conditions.
Ecological Indicators, 2008
On a worldwide-scale coastal, estuarine and transitional waters have been affected by man's activities. Historically, developing human civilizations has often been concentrated in coastal areas where access to water promoted trade, commerce, and disposal of wastes (e.g., van Andel, 1981). As a consequence, human alteration of natural ecosystems is profound in coastal areas and a central theme of environmental management is to develop policy to balance socioeconomic growth and environmental protection. A central concept of environmental management is maximizing beneficial sustainable development while minimizing impacts to ecological integrity (Mü ller, 2005). In order to deal with the complexities of socio-environmental issues, many countries have adopted the DPSIR (drivers-pressure-state-impactresponse) approach (e.g.