Classification Of Ecological Status Research Articles

HABITAT‐ORIENTED SAMPLING OF MACROINVERTEBRATES AFFECTS THE DETERMINATION OF ECOLOGICAL STATUS IN TEMPORARY MEDITERRANEAN RIVER SYSTEMS

ABSTRACTInter‐annual and annual variation in precipitation levels in Mediterranean temporary river systems strongly influence riverine flow regimes and as a result habitat' availability for biological assemblages. Under‐sampling of less well‐presented microhabitats in such changeable, dynamic systems can result in information loss leading to misclassification of Water Framework Directive (WFD) compliant ecological status, with serious consequences for Programmes of Measures in River Basin Management Plans. This paper compares two benthic macroinvertebrate sampling protocols tested in intermittent Mediterranean streams (n = 40) in the Algarve region of southern Portugal. The officially adopted WFD compliant European assessment system for the ecological quality of rivers using benthic macroinvertebrates, a composite sampling protocol, focuses sampling a greater area of the most representative microhabitats at a given sampling site (proportional habitat sampling). A non‐proportional habitat sampling protocol was applied to test the assumption that taxa may have preference for different microhabitats and that this could influence classification of ecological status. Variation was detected in the levels of similarity in the structure and the composition of the benthic macroinvertebrate community within sampling sites and rivers, based on material collected using the two collection methods. Ecological index scores and biotic metrics were higher when the non‐proportional oriented sampling protocol was utilized resulting in a ‘good ecological status’ classification at sites that had been classified as ‘Bad’ using the official WFD, Decision tree analysis results indicated that changes in the area of individual microhabitats sampled among protocols was the principal driver behind differences in ecological status derived. The results indicate that more realistic classifications could be achieved in intermittent Mediterranean rivers when considering and sampling less well‐represented microhabitat types (non‐proportional sampling) rather than distributing sampling effort by the proportion of the dominant habitat present as currently used for the WFD protocol. The application of the non‐proportional microhabitat‐based approach, which accounts for selective preferences of some benthic macroinvertebrate taxa, would ensure that a greater proportion of a given site community contributes to the assessment. Copyright © 2014 John Wiley & Sons, Ltd.

Development of a new biotic index for ecological status assessment of Italian coastal waters based on coralligenous macroalgal assemblages

This paper presents a new biotic index (ESCA, Ecological Status of Coralligenous Assemblages), based on analyses of in situ records of coralligenous macroalgal assemblages in the Mediterranean Sea. The ESCA index was developed on the basis of previous impact evaluation studies carried out by traditional destructive methods. It was validated on an independent dataset collected during a 3-year study carried out at five localities in the north-western Mediterranean, and tested on a gradient of anthropogenic stressors. Assemblage descriptors selected as metrics of the ESCA index were: (a) presence/absence and abundance of sensitive taxa/groups (expressed as sensitivity level of assemblages, SL), (b) diversity of assemblages (expressed as α-diversity) and (c) heterogeneity of assemblages (expressed as β-diversity). The three metrics were combined to give a final value for the multimetric ecological index, Ecological Quality Ratio, calculated as the ratio between the measured values and the value obtained in the reference condition. The Ecological Quality Ratio values ranged from 0 to 1 and five ecological status classes were defined in accordance with the Water Framework Directive. The ESCA index could be used to define the ecological status of the studied sites, providing differences between assemblages similar to those shown by multivariate analyses. Moreover, ecological quality values were quite steady throughout the study period. The ESCA index may represent a useful tool for monitoring programmes in coastal waters, since it has been developed in compliance with the Water Framework Directive; it synthesizes complex information in a simple and reliable way; and its application is simple and cost-effective. However, further studies are necessary to complete index development and to properly evaluate its strengths and weaknesses on a larger scale.

Benthic macrophyte metrics as bioindicators of water quality: towards overcoming typological boundaries and methodological tradition in Mediterranean and Black Seas

Benthic macrophyte communities of dif- ferent substratum types (soft, hard) were studied in eleven differently impacted sites belonging in two different water typologies (transitional waters: Lesina Lagoon, Varna Lake; coastal waters: Varna Bay) and two ecoregions (Mediterranean Sea, Black Sea). Species lists were compiled for each study site, 20 taxa were found at Lesina and Varna Lake and Bay, and the abundance of each taxon was determined at each site. The relationship between nine metrics related to community structure (species richness, % of total coverage, dry biomass (g/m -2 ), and cluster and multi-dimensional scaling plot of Bray-Curtis simi- larity) and function (Ecological Status Group I % coverage, ESG II % coverage, Ecological Evaluation Index (EEI-c) and Ecological Index (EIEEI)) and key abiotic factors and an anthropogenic stress index (EnII) were studied. A strong relationship (Spearman rank correlation coefficient q B- 0.89; R 2 C 0.89) between anthropogenic stress and functional indices, EEI-c and EIEEI, was found. The structural index 'species richness' correlated negatively with EnII and positively with salinity, demonstrating a freshwater and confinement influence on species diversity. EEI-c and EIEEI indices classified the studied sites and locations in different Ecological Status Classes in accordance with the anthropogenic stress gradient.

Defining ecologically relevant water quality targets for lakes in Europe

Summary The implementation of the Water Framework Directive requires EU member states to establish and harmonize ecological status class boundaries for biological quality elements. In this paper, we describe an approach for defining ecological class boundaries that delineates shifts in lake ecosystem functioning and, therefore, provides ecologically meaningful targets for water policy in Europe. We collected an extensive data set of 810 lake‐years from nine Central European countries, and we used phytoplankton chlorophyll a, a metric widely used to measure the impact of eutrophication in lakes. Our approach establishes chlorophyll a target values in relation to three significant ecological effects of eutrophication: the decline of aquatic macrophytes, the dominance of potentially harmful cyanobacteria and the major functional switch from a clear water to a turbid state. Ranges of threshold chlorophyll a concentrations are given for the two most common lake types in lowland Central Europe: for moderately deep lakes (mean depth 3–15 m), the greatest ecological shifts occur in the range 10–12 μg L−1 chlorophyll a, and for shallow lakes (<3 m mean depth), in the range 21–23 μg L−1 chlorophyll a. Synthesis and applications. Our study provides class boundaries for determining the ecological status of lakes, which have robust ecological consequences for lake functioning and which, therefore, provide strong and objective targets for sustainable water management in Europe. The results have been endorsed by all participant member states and adopted in the European Commission legislation, marking the first attempt in international water policy to move from physico‐chemical quality standards to harmonized ecologically based quality targets.

Comparison of two indices based on macrophyte assemblages to assess the ecological status of coastal waters in the transition between the Atlantic and Mediterranean eco-regions

Several indices based on the composition and abundance of aquatic flora have been developed to assess the ecological status of coastal waters along the European coasts in the context of the Water Framework Directive. This directive pointed out the intercalibration of indices based on the same biological element within an eco-region to ensure the consistency and comparability among them. For a better management of coastal areas in the transition zone between two eco-regions, the comparison of indices developed for each eco-region may also be necessary. The aim of this work was to compare two indices based on macrophytes that have been proposed for two different and adjoining eco-regions: the RSL (Reduced Species List) in the Atlantic eco-region and the CARLIT (Cartography of littoral and upper sublittoral communities) in the Mediterranean. These indices were applied in 14 sites in the transition between the Atlantic Ocean and the Mediterranean Sea, where a wide range of anthropogenic pressures can be found, from high (Algeciras Bay) to almost negligible ("El Estrecho" Natural Park). Overall, both indices were sensitive to anthropogenic pressures and suitable to assess the ecological status. The comparison between indices suggested a bias in the assessment of the ecological status between good and high classes due to a different definition of high ecological status class between RSL and CARLIT. In addition, the most important disagreements between indices were found in the most degraded localities. The results showed, however, a high comparability between RSL and CARLIT despite their marked conceptual and methodological differences.

Water quality assessment of rivers using diatom metrics across Mediterranean Europe: A methods intercalibration exercise

The European Water Framework Directive establishes a framework for the protection of water resources. However, common water management tools demand common understanding of assessment methods, so quality goals are equally met. Intercalibration of methods ensures the comparability of biological elements across similar geographical areas. Many aspects can influence the outcome of intercalibration: data sampling, treatment methods, taxonomic reliability of databases, choice of metrics for ecological quality status classification, and criteria for selecting reference sites. This study describes the potentials and constraints of the intercalibration of indices using diatoms for assessment of Mediterranean rivers. Harmonisation of diatom taxonomy and nomenclature was based on a previous ring test which took place at the European level. Four diatom indices (Indice de Polluosensibilité Spécifique—IPS, Indice Biologique Diatomées—IBD 2007, Intercalibration Common Metric Italy—ICMi and Slovenian Ecological Status assessment system) were intercalibrated using data from six European Mediterranean countries (Cyprus, France, Italy, Portugal, Slovenia and Spain). Boundaries between High/Good and Good/Moderate quality classes were harmonised by means of the Intercalibration Common Metric (ICM). Comparability between countries was assured through boundary bias and class agreement. The national boundaries were adjusted when they deviated more than a quarter of a class equivalent (0.25) from the global mean.All national methods correlated well with the ICM, which was sensitive to water quality (negatively correlated to nutrients). Achnanthidium minutissimum sensu lato was the most discriminative species of Good ecological status class. Planothidium frequentissimum, Gomphonema parvulum and Nitzschia palea were the most contributive to Moderate ecological status class. Some taxa were discriminative for both Good and Moderate ecological status classes due to low indication and ecological discriminative power but also due to differences in taxonomy between countries.This intercalibration exercise allowed establishment of common water quality goals across Mediterranean Europe, which is substantiated with the ICM.

Objective classification of ecological status in marine water bodies using ecotoxicological information and multivariate analysis

Some relevant shortcomings have been identified in the current approach for the classification of ecological status in marine water bodies, leading to delays in the fulfillment of the Water Framework Directive objectives. Natural variability makes difficult to settle fixed reference values and boundary values for the Ecological Quality Ratios (EQR) for the biological quality elements. Biological responses to environmental degradation are frequently of nonmonotonic nature, hampering the EQR approach. Community structure traits respond only once ecological damage has already been done and do not provide early warning signals. An alternative methodology for the classification of ecological status integrating chemical measurements, ecotoxicological bioassays and community structure traits (species richness and diversity), and using multivariate analyses (multidimensional scaling and cluster analysis), is proposed. This approach does not depend on the arbitrary definition of fixed reference values and EQR boundary values, and it is suitable to integrate nonlinear, sensitive signals of ecological degradation. As a disadvantage, this approach demands the inclusion of sampling sites representing the full range of ecological status in each monitoring campaign. National or international agencies in charge of coastal pollution monitoring have comprehensive data sets available to overcome this limitation.

Development of an estuarine multi-metric fish index and its application to Irish transitional waters

An estuarine multi-metric fish index (EMFI) was developed and applied to Irish transitional waters. The index comprised a balanced and complimentary set of 14 metrics that represent four fish community attributes: species diversity and composition, species abundance, estuarine utilisation, and trophic composition. Reference conditions and metric scoring thresholds were developed using a combination of historical records, best available data, and expert judgement. The index was applied using representative and robust fish monitoring data collected using a suite of methods designed to cover a range of habitats and conditions. To ensure consistency and comparability, all systems were considered at the whole estuary level. A sensitivity analysis was carried out to assess the response of the EMFI under various scenarios of metric change; five metrics were consistently among the most influential on the EMFI in all scenarios of metric manipulation. The overall EMFI was significantly correlated with environmental condition as measured by two separate indicators of ecological state. Ecological status classes were also established based on the relationship between the EMFI and an index of human pressure. The EMFI provides a robust, sensitive, and integrated measure of the ecological status of fishes in transitional waters and meets the requirements of the EU Water Framework Directive.

M-AMBI derived from taxonomic levels higher than species allows Ecological Status assessments of benthic habitats in new geographical areas

Under the Water Framework Directive (WFD) benthic Ecological Quality Ratios (EQRs) are important tools for assessing Ecological Status (ES) of coastal and transitional waters. Calculation of the Multivariate-AZTI Marine Biotic Index (M-AMBI) EQR is based on the proportions of sensitive and stress tolerant benthic invertebrate species, number of species and Shannon–Wiener diversity. The sensitivity of many tropical/sub-tropical taxa has not yet been determined, presenting a barrier to the direct transfer of WFD EQRs, and the ideas underpinning them, to the management of coastal waters beyond Europe. To overcome this we examine using higher taxonomic level data with M-AMBI.Before applying such approaches to assessing ES in new geographical regions it is essential to determine the effects of using higher taxonomic level data on M-AMBI in areas where the tool was developed. To this end, we use macrofaunal data from three well studied sites in north-western Europe to examine the effects of using taxonomic level data higher than species on M-AMBI. Using the European datasets M-AMBI ES classification was shown to be robust to changes in taxonomic level data. We test the suitability of family-level M-AMBI for assessing ES in subtropical Hong Kong waters. Family level M-AMBI was useful in detecting stress in Hong Kong, where it successfully detected temporal and spatial shifts in ES in response to seasonal hypoxia and salinity variability, and anthropogenic organic enrichment.

Relocation of dredged material in estuaries under the aspect of the Water Framework Directive—A comparison of benthic quality indicators at dumping areas in the Elbe estuary

In the context of the requirements of the European Water Framework Directive (WFD) numerous benthic indices have been proposed recently to assess the ecological quality of marine and transitional waters. In several studies these metrics were applied to coastal and estuarine environments under diverse anthropogenic pressures. Although currently the dumping of dredged material is one of the most prominent human impacts that modify estuaries, the performance of benthic indices to detect effects of dredged sediment relocation has not yet been tested explicitly. Hence we examined a selection of common metrics (species richness, Shannon diversity, AMBI, M-AMBI, W-value, BO2A) at 11 dumping and 11 nearby reference areas in the highly modified Elbe estuary (Germany), where permanent dredging is necessary to maintain the depth of the navigation channel. In order to cover the entire estuary, the study area spanned over the whole salinity gradient from limnic to euhaline. Additionally, we investigated changes in benthic communities due to dredged material placement. All indices, except the W-value, were suitable to differentiate between dumping and reference areas and showed significantly better index values exclusively at reference areas. The applicability of AMBI and M-AMBI was restricted in the limnic stretch due to the more frequent occurrence of freshwater species there. The W-value and BO2A were non-satisfactory in the case of azoic sediment, and in most cases these two indices indicated much better ecological status classifications than the other indices tested. Furthermore, the BO2A had restricted applicability with increasing salinity. At eight of eleven sites the benthic communities differed significantly between dumping and reference areas. Our findings show that the power of conventional benthic indices to detect physical disturbances like the dumping of dredged sediment varies greatly. Having this in mind, we suggest to choose carefully the benthic indices for ecological quality assessments according to the WFD in estuaries in order to avoid misclassifications. Such errors may lead to unnecessarily expensive remediation activities or, in the opposite case, to inactivity although actions were necessary. Furthermore, in order to better meet the WFD requirements we suggest that, regarding frequency and volume, dumping should be adapted as far as possible to the natural processes of sediment movement.

A hierarchical Bayesian model for the ecological status classification of lagoons

In transitional waters and among Water Framework Directive (WFD) (European Parliament, 2000) quality elements, benthic macroinvertebrates are the most exposed to natural variability patterns characteristic of these ecosystems due to their life cycles and space-use behaviour. Here, we address the ecological status classification issue for Mediterranean and Black Sea lagoons, using benthic macroinvertebrates from a set of 13 reference lagoons. Two main classification approaches have been proposed in literature: the a priori approach, based on standard classification boundaries, and the a posteriori approach, based on classification boundaries set according to linear mixed models. However, the two approaches take into account only partially and at a different extent the natural variability of ecosystem properties, which may lead to inaccuracies of the classification procedure. Moreover, the different proposed multimetric indices are likely to respond differently to different source of stress and natural variability components, adding uncertainty to the classification procedure. We propose a Bayesian hierarchical model in which the multimetric indices are jointly modelled through a multivariate normal mixture, in order to emphasize clusters of ecosystems resulting from the integration of different multimetric indices. Each mixture component is estimated as function of covariates of interest and corresponds to a cluster of sites assumed to be a proxy of a class of ecological status. This assumption has been validated on a set of ecosystems already classified into ecological status classes with standard methods. We apply the model to available data and compare the classification obtained by the proposed model with those given by the a priori and a posteriori approaches, highlighting pros and cons of each method.

Ability of phytoplankton trait sensitivity to highlight anthropogenic pressures in Mediterranean lagoons: A size spectra sensitivity index (ISS-phyto)

Size spectra exhibit common patterns of variation and predictable responses to pressures across ecosystem types, functional guilds and taxonomic groups. Here, we extend the size spectra approach to phytoplankton ecological status assessment in transitional waters by developing, testing and validating a multi-metric index of size spectra sensitivity (ISS-phyto), which integrates size structure metrics with others such as phytoplankton diversity, biomass and sensitivity of size classes to anthropogenic disturbance. The ability of various theoretical models of size spectra sensitivity to discriminate between disturbed and undisturbed ecosystems and levels of anthropogenic stress was evaluated. We used data on phytoplankton samples collected in 14 Mediterranean and Black sea transitional water ecosystems (coastal lagoons) from Italy, Albania, Greece, Bulgaria and Romania, and compared the models’ efficiency by looking at their pressure–impact response along salinity and enrichment gradients, the latter quantified as variations in dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP). Data from a fifteenth Mediterranean lagoon was used for external validation purposes. Right asymmetric models of size class sensitivity, implying higher sensitivity of smaller cell size classes, were found to contribute to the ISS-phyto multimetric tool more effectively than symmetric and left asymmetric models, distinguishing disturbed from undisturbed lagoons and disturbed from undisturbed stations within the same lagoon. When based on right asymmetric sensitivity models, i.e., those that were most efficient in identifying anthropogenic impacts, ISS-phyto also showed the best fit of pressure–response relationships along the salinity and enrichment gradients; at low to high levels of impact ISS response was driven by size class sensitivity and at very high impacts by phytoplankton biomass. A scheme for the classification of Ecological Quality Status based on ISS-phyto is proposed and validated. The validation procedure found that ISS-phyto is an effective and sensitive monitoring tool, robust, easy to apply and to inter-calibrate among laboratories.

Intercalibrating classifications of ecological status: Europe's quest for common management objectives for aquatic ecosystems

Halting and reversing the deterioration of aquatic ecosystems requires concerted action across state boundaries and administrative barriers. However, the achievement of common management objectives is jeopardised by different national quality targets and ambitions. The European Water Framework Directive requires that quality classifications are harmonised via an intercalibration exercise, ensuring a consistent level of ambition in the protection and restoration of surface water bodies across the Member States of the European Union. We outline the key principles of the intercalibration methodology, review the achievements of intercalibration and discuss its benefits and drawbacks. Less than half of the required intercalibration has been completed, mostly due to a lack of national assessment methods. The process has fostered a scientific debate on ecological classification with important implications for environmental management. Despite a significant level of statistical abstraction, intercalibration yielded a fundamental and unified vision of what constitutes good ecology across Europe, in principle ensuring greater parity in the funds invested to achieve good ecological status.

Can lake restoration by fish removal improve the status of profundal macroinvertebrate assemblages?

Summary Removal of fish to restore lake pelagic food webs and water quality has been shown to increase the abundance of benthic invertebrates in shallow areas due to decreased predation pressure, while responses of profundal macroinvertebrate assemblages are less well documented. We used multivariate analyses and a Before‐After‐Control‐Impact design to assess the impacts of fish removal (in total 101 000 kg of percid and cyprinid fish) on profundal macroinvertebrate species composition and abundance and ecological status in two basins of a eutrophic boreal lake. In the deeper main basin, macroinvertebrate community composition and classification of ecological status were not affected by fish removal, although changes in chironomid abundance and relative abundances of predominant oligochaete taxa were observed. By contrast, in the shallower basin, community response to fish removal was more pronounced and characterised by a marked decrease in abundances of pollution‐tolerant chironomid and oligochaete taxa, resulting in change in community composition and improvement in the ecological status. Fish removal resulted in no change in trophic state of Lake Jyväsjärvi; hence, the mechanism(s) responsible for the observed changes in profundal assemblages are unclear. A decrease in turbidity and an increase in Secchi depth suggest that concentrations of suspended solids may have decreased, resulting in lower planktic microbial production, indirectly affecting macroinvertebrate community structure. Our results indicate that a 3‐year fish reduction may have been too short to achieve complete recovery of the benthic communities, suggesting that prolonged food‐web management together with a greater reduction in nutrient loading is needed.

From expert judgement to supervised classification: A new approach to assess ecological status in lowland streams

The EC Water Framework Directive (WFD) clearly states that undisturbed reference states of aquatic ecosystems should be used to set standards for restoration. Across Europe defining biological reference status and setting boundaries for ecological status classes continues to represent a major challenge. In the present study we investigate if a paradigm exists among experts that can guide the development of assessment systems based on the normative definitions of ecological status classes of the WFD. Our main questions were: 1) Will experts from species abundance data and typology descriptors independently arrive at similar assessments of ecological status, and 2) Can the expert interpretation of ecological status be transferred into a statistical model allowing for a standardization of assessments from plant assemblages in lowland streams? We used a large dataset covering 1244 randomly distributed stream sites in Denmark and asked a group of experts to independently classify the sites using the WFD's normative definitions of ecological status. According to the combined expert group, no Danish stream sites belonged to the undisturbed reference state. For the remaining ecological status classes we found good concordance in the classification made by the five experts. From this we infer that a common paradigm does exist, which may guide the development of assessment methods for aquatic plants in lowland streams. We also found that the common view of the experts could be transferred into a supervised classification model that can serve as a classification tool for aquatic plant assemblages in lowland streams. We conclude that the combined use of experts and advanced multivariate statistics can provide a useful approach in the development of systems for assessment of ecological status in water types, where a reference network cannot be established.

Gill histopathological and oxidative stress evaluation in native fish captured in Portuguese northwestern rivers

The Northwestern Portuguese region is densely populated and highly industrialized, suffering from high anthropogenic pressure. To assess the biological effect of the several pollutants that are constantly released to the water, a biomarker-based biomonitoring is a promising approach that may provide early-warning signals of pollutants exposure. Fish gill is the first target of pollutants action, thus histopathological and biochemical changes may constitute potential biomarkers. To evaluate this hypothesis, three native fish species (barbel—Luciobarbus bocagei, chub—Squalius carolitertii and nase—Pseudochondrostoma sp.) were sampled in Northwestern Portuguese rivers, the gill histopathological changes were qualitative and quantitatively analyzed and the lipid peroxidation and glutathione-S-transferase activity were determined. A multivariate statistical analysis was performed to establish correlations between these biological responses, environmental variables and ecological status. The quantitative evaluation of the main histopathological changes and oxidative stress responses emphasize the differences, among species, in the responses to the presence of contaminants in water. Discriminant canonical analysis showed that filament epithelium proliferation, necrosis and GST activity were the main contributors to discriminate the ecological status classification. In addition, the results showed that a wide range of environmental factors are influencing fish physiology. In conclusion, the gill biological responses, although not reflecting specific contaminants, can be used as biomarkers of ecosystems perturbation.

Integrated Assessment of the Ecological Status of Bulgarian Lowland and Semi-Mountain Natural Lakes

This work focuses on an integrated approach for lake ecological status assessment, elaborated according to the requirements of the European Water Framework Directive (WFD). Data from five lowland and semi-mountain lakes in Bulgaria (Southeast Europe) collected from two years (2011-2012) form the basis for an integrated assessment and the definition of reference conditions. Several metrics were applied in combination, to classify lakes into five ecological status classes. Assemblages of aquatic organisms: phytoplankton, macrophytes and benthic macroinvertebrates, together with 11 supporting physico-chemical parameters were studied. The assessed unique conditions suggested that reference conditions of Bulgarian lakes have natural variability. This first baseline study illustrated specific cases within the lake types that should be assessed in details before providing standardized classification systems in compliance with the requirements of WFD.

Exploring the robustness of macrophyte-based classification methods to assess the ecological status of coastal and transitional ecosystems under the Water Framework Directive

Identifying and quantifying the factors that contribute to the potential misclassification of the ecological status of water bodies is a major challenge of the Water Framework Directive (WFD). The present study compiles extensive biomonitoring data from a range of macrophyte-based classification methods developed by several European countries. The data reflect spatial and temporal variation as well as inter-observer variation. Uncertainty analysis identified that factors related to the spatial scale of sampling generally contributed most to the uncertainty in classifying water bodies to their ecological status, reflecting the high horizontal and depth-related heterogeneity displayed by macrophyte communities. In contrast, the uncertainty associated with temporal variation was low. In addition, inter-observer variation, where assessed, did not contribute much to overall uncertainty, indicating that these methods are easily transferable and insensitive to observer error. The study, therefore, suggests that macrophyte-based sampling schemes should prioritize large spatial replication over temporal replication to maximize the effectiveness and reliability of water body classification within the WFD. We encourage conducting similar uncertainty analyses for new/additional ecological indicators to optimize sampling schemes and improve the reliability of classification of ecological status.

Ecological status assessment and response of benthic communities to environmental variability: The Valli di Comacchio (Italy) as a study case

The Valli di Comacchio is one of most representative choked (not influenced by the tidal regime) lagoons in the Mediterranean and Europe. We compared the ecological status (ES) classification (sensu European Water Framework Directive, 2000/60/EC) of the Valli obtained through supporting physicochemical elements and biotic indices. The variability of water parameters was investigated through 1997–2002 at 4 permanent sampling stations. During the six years of investigation, macrobenthic data were collected to identify the response of several biological indices (taxonomic, functional and ecological). ES classification through supporting physicochemical elements resulted in discordant patterns. Nor taxonomic neither functional measures were able to add more information than that given by univariate biodiversity measures. Gaps and bias of the indices used were identified. Due to the absence of well defined environmental gradients, taxonomic and functional measures loose most of their usefulnesses. ES classification through ecological indices (M-AMBI and BITS) resulted in quite a concordant pattern, although BITS underestimated ES when there was a strong dominance of one opportunist family in the benthic community.

Natural variability and reference conditions: setting type-specific classification boundaries for lagoon macroinvertebrates in the Mediterranean and Black Seas

The ecological status classification of aquatic ecosystems using biological indices requires a number of steps, including the description and standardisation of the indices’ natural variability. Here, we address this point with reference to selected Mediterranean and Black Sea lagoons, using benthic macroinvertebrates in order to: (i) explore the drivers and extent of the indices’ natural variability; (ii) evaluate lagoon type-specific reference conditions and related classification boundaries; (iii) test the classification strength of the derived boundaries; and, (iv) propose recommendations for optimising ecological status classification. The considered indices showed large variation between and within the reference lagoons on both spatial and temporal scales. Among the tested descriptors of the proposed lagoon typologies, surface area, confinement and water salinity were found to be significant sources of index variability. Type-specific reference conditions and classification boundaries were then defined, improving the accuracy of ecological status assessment. At the lagoon level, classification strength increased up to 100 % in reference (least disturbed) lagoons and up to 83 % in an independent validation set of highly disturbed sites. Nevertheless, a certain degree of uncertainty was still found to affect classification at the study site level. Recommendations concerning the application of the various approaches to type-specific reference conditions and classification boundaries are given.