Macrophyte‐based assessment of lakes – a contribution to the implementation of the European Water Framework Directive in Germany

The European Water Framework Directive requires ecological status classification and monitoring of surface and ground water bodies using biological indicators. To fulfill the demands of the Directive, a macrophyte‐based assessment system was developed for application on four lake site types in Germany. Biological lake site types were established using differences in characteristic macrophyte communities, reflecting ecoregion, Ca²⁺ content, mixis and morphology. Ecological status classification of lake sites is based on macrophyte abundance along 275 transects in 95 natural German lakes and the calculation of a reference index value, in some cases supplemented by submerged vegetation data. The reference index quantifies the deviation of species composition and abundance from reference conditions and classifies sites to one of the five ecological quality classes specified in the Directive. Based on an example of Lake Chiemsee, Germany, the possibilities for a wholelake assessment are discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ecological quality scales based on phytoplankton for the implementation of Water Framework Directive in the Eastern Mediterranean

Structural changes of phytoplankton communities, often expressed through ecological indices, constitute one of the metrics for the implementation of the European Water Framework Directive (WFD). In the current study a thorough analysis of the efficiency of 22 ecological indices was performed and a small number was selected for the development of five-level water quality scales (High, Good, Moderate, Poor, and Bad). The analysis was performed on simulated communities free of the noise of field communities due to uncontrolled factors or stochastic processes. Two criteria were set for the sensitivity of indices, namely their monotonicity and linearity across the studied eutrophication spectrum. The whole procedure was based on the development of a five-level quality assessment scheme based on phytoplankton abundance. Among the indices tested, the Menhinick diversity index and three indices of evenness were the most efficient, showing consistency (monotonic behavior) and linearity and were therefore used for the development of quality scales for the WFD. An Integrated Phytoplankton Index (IPI) based on three phytoplankton metrics, chlorophyll a, abundance, and diversity is also proposed. The efficiency of these indices was evaluated for a number of sites in the Aegean, already classified in the past by various methods based on nutrient concentrations or phytoplankton data. The results indicate that the various phytoplankton metrics (chlorophyll a, abundance, and diversity) assessed or proposed in the current study, carry their own information showing differences in the final classification of areas. Therefore the establishment of synthetic indices as the IPI seems to be advantageous for the integrated assessment of coastal water quality in the framework of European policies as the WFD.     

First steps in the Central-Baltic intercalibration exercise on lake macrophytes: where do we start?

The Water Framework Directive (WFD 2000) defines macrophytes as one of the biological groups required for the ecological assessment of European surface waters. Several indices for macrophyte assessment have been proposed or are currently in use by different European states. As a first step towards performing an intercalibration of these indices a common dataset was developed. This dataset contains abundance data on 789 macrophyte species from 316 different lake sites in ten European countries. Various common species and genera were identified as indicators of reference and impacted conditions within the dataset. Cluster analysis of macrophyte data, supported by non-metric multidimensional scaling, indicated that clusters formed were more reflective of their source country rather than lake type. This might be caused by differences in regional climate, biogeography, monitoring techniques, or a combination of these factors. A total of six national indices were applied to assign quality classes to the lakes. However, this produced results that often differed by one or two quality classes for the same site. We foresee that a more precise intercalibration exercise is necessary, and it should be based on more detailed data considering both seasonality and the latitudinal differences within the area covered.     

The Reference Index Method for the Macrophyte‐BasedAssessment of Rivers – a Contribution to the Implementationof the European Water Framework Directive in Germany

The European Water Framework Directive requires ecological status classification and monitoring of surface and ground waters using biological indicators. To act as a component of the “Macrophytes and Phytobenthos” biological quality element, as demanded by the Directive, a macrophyte‐based assessment system was developed for application in river site types in Germany. Macrophyte abundance data were collected from 262 sites in 202 rivers. Seven biocoenotic river site types were established using differences in characteristic macrophyte communities reflecting ecoregion, channel width, water depth, current velocity, water hardness, and ground water influence. For four of these river site types, a macrophyte assessment system was developed, for the remaining three river site types data were insufficient for developing an assessment system. Ecological status classification of river sites is based on the calculation of a Reference Index value, in some cases supplemented by additional vegetation criteria. The Reference Index quantifies the deviation of species composition and abundance from reference conditions and classifies sites as one of the five possible ecological quality classes specified in the Directive. The assessment of long river stretches with changing river site types along its course is discussed based on an example from the Forstinninger Sempt River, southeast Germany. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of sampling effort on metrics of fish-based indices for the assessment of estuarine ecological quality

Multimetric fish-based indices have been increasingly gaining importance in Europe, as the Water Framework Directive (WFD) requires fish fauna, and particularly its composition and abundance, to be taken into account in the assessment of the ecological quality of continental surface waters, including transitional waters. These indices are composed of several metrics, mostly related with structural and functional characteristics of fish communities, such as species richness, the role of nursery areas, or trophic web structure. Therefore, ecological quality assessments should ensure that these structural and functional characteristics of fish communities were covered by the sampling methods used. In the present work, the influence of sampling effort on several metrics of the Estuarine Fish Assessment Index (EFAI) was studied. Pseudo-random samples were generated from data of four Portuguese estuaries and bootstrap cycles were performed, in order to obtain metrics’ means and standard deviations per number of hauls analysed. The number of hauls necessary for the means to level off differed with the metrics considered. Generally, for metrics on percentages (percentage of marine migrants, percentage of estuarine residents and percentage of piscivores) the curve levelled off with less than 20 hauls, both for the estuary as a whole and for different estuarine salinity zones. On the other hand, metrics on species richness required much larger samples. In order to decrease to −5% the current estimated bias of metrics, the WFD sampling costs would have to be more than 3 times higher than they currently are. The findings in the present study are of great importance for an effective assessment of estuarine ecological quality and particularly in the context of the WFD, as the metrics studied are common to other Member State indices.     

Dynamics of the shallow-water fish assemblage of the Patos Lagoon estuary (Brazil) during cold and warm ENSO episodes

In southern Brazil, cold ( La Niña ) and warm ( El Niño ) episodes of the El Niño Southern Oscillation (ENSO) phenomenon cause drought and high rainfall, respectively. The low precipitation and freshwater outflow associated with La Niña during 1995–1996 were associated with an increase in the abundance of marine species in the Patos Lagoon estuary. During the 1997–1998 El Niño , high precipitation and river discharge were associated with low abundance of marine species in the estuary. ANOVA results showed a higher abundance during La Niña than El Niño for estuarine resident (RES) and estuarine dependent (DEP) fishes. During La Niña catch per unit of effort (CPUE) of RES increased from the marine to estuarine area, but during El Niño CPUE increased at the marine area and diminished during summer and autumn in some estuarine sites. DEP fishes had an opposite abundance pattern. During La Niña , these fishes were abundant at the coastal marine area and along some estuarine sites, but during El Niño , CPUE remained almost the same at the marine area but dropped along some estuarine sites. These different abundance patterns for dominant fish groups yielded a positive interaction between stations and climatic events. With higher river discharge and the consequent decline of dominant euryhaline fishes, such as Mugil platanus and Atherinella brasiliensis , freshwater species increased in abundance and richness in the shallow waters of the stuary. The ENSO phenomenon influences precipitation and estuarine salinity in southern Brazil and thereby seems to have a strong influence on recruitment, immigration, and emigration dynamics of fish species living within and adjacent to estuarine habitats.     

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.     

Geographical and typological changes in fish guilds of South African estuaries

A comparative analysis of fish estuary association guilds was undertaken on some 190 South African estuaries. This pioneering study spanned three zoogeographic regions and included three broad estuarine types. The guild compositions of the estuaries were compared based on an importance value, incorporating taxonomic composition, numerical abundance and relative biomass. Multivariate analyses included both inter‐regional (zoogeographic) and intra‐regional (estuarine typology) comparisons. The major estuary‐associated guilds (estuarine species and marine migrant species) were important in all estuary types within all biogeographic regions. Significant differences both between regions and between estuary types within regions, however, were recorded. Cool–temperate estuaries were generally dominated by migratory species (estuarine migrants and marine migrant opportunists) while the importance of species dependent on estuaries (estuarine residents and estuarine‐dependent marine migrants) was higher in warm–temperate and subtropical regions. The significance of estuarine nursery areas, particularly in regions where estuaries are few in number, is highlighted. In terms of typology, migratory species assumed a greater importance in predominantly open systems, while freshwater and estuarine‐resident species were more important in predominantly closed systems. Predominantly closed estuaries, however, were also important for marine migrant species, which further highlights the significance of these systems as nursery areas for fishes.     

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.     

The performance of trait-based indices in an estuarine environment

The performance of several indices of benthic functioning, based on the traits of estuarine macro-invertebrates, was tested in the lower Mondego estuary (Portugal), whose two arms exhibit different disturbance levels related to hydromorphology. The results showed that some indices responded clearly to this type of disturbance and others not so well. We argue that the community-weighted mean trait values (CWM) in combination with the newly developed SR-FRED index provided the best overall picture of how the benthic communities might have been affected by hydromorphological disturbance. This study also showed that certain indices should be used with caution when dealing with communities with few and dominant species, such as in estuarine environments.     

Developing a classifier for the Habitats Directive grassland types in Denmark using species lists for prediction

Abstract. This paper describes the use of supervised methods for the classification of vegetation. The difference between supervised classification and clustering is outlined, with reference to their current use in vegetation science. In the paper we describe the classification of Danish grasslands according to the Habitats Directive of the European Union, and demonstrate how a supervised classification can be used to achieve a standardized and statistical interpretation within a local flora. We thereby offer a statistical solution to the legal problem of protection of certain selected habitat types. The Habitats Directive protects three types of Danish grassland habitats, whereas two remaining types fall outside protection. A classification model is developed, using available Danish grassland data, for the discrimination of these five types based on their species composition. This new Habitats Directive classification is compared to a previously published unsupervised classification of Danish grassland vegetation. An indicator species analysis is used to find significant indicator species for the three protected habitat types in Denmark, and these are compared to the characteristic species mentioned in the interpretation manual of the Habitats Directive. Eventually, we discuss the pros and cons of supervised and unsupervised classification and conclude that supervised methods deserve more attention in vegetation science.     

Plant species composition in relation to green cover configuration and function of urban parks in Beijing, China

Parks, as one specific type of urban open space, play important roles in the conservation of urban biodiversity and provision of recreational services for local residents. As there is a lack of specific insight into park plant species composition in relation to park features, 24 sample parks within the inner city of Beijing, the capital of China, were studied by stratified random plot sampling of their tree, shrub, and herbaceous communities, respectively, in order to investigate how human activities have influenced park green cover configuration and floristic characteristics. The quantitative correlation of species richness and the park green cover indices (patch size, shape, etc.) were studied. The importance value index for plant species (trees, shrubs, and herbaceous species) of each park was calculated. The two-way indicator species analysis approach (TWINSPAN) was applied to classify the 24 parks into different groups based on their species assemblages. Two-hundred and eighty-eight species were recorded within the 24 study parks, belonging to 184 genera and 72 families dominated by Gramineae, Compositae, and Leguminosae. Among all the recorded species, 41% are exotic. The species occurrence, abundance and diversity vary significantly among different parks. Besides the positive correlation (R=0.505, P<0.05) between herbaceous species abundance and the park green cover size, no other significant relations were found between the species abundance and other indices of park green cover configuration. Remarkably, the TWINSPAN classification resulted in a good discrimination between park functional types and the variation in their species assemblage. For the parks of similar age (development history) or landscape design, their species assemblages show more similarity. The methodology adopted and results can be employed to improve baseline information on urban plant ecology and support the setting of priorities for future park management and vegetation protection.     

A new statistical approach for assessing similarity of species composition with incidence and abundance data

The classic Jaccard and Sørensen indices of compositional similarity (and other indices that depend upon the same variables) are notoriously sensitive to sample size, especially for assemblages with numerous rare species. Further, because these indices are based solely on presence–absence data, accurate estimators for them are unattainable. We provide a probabilistic derivation for the classic, incidence‐based forms of these indices and extend this approach to formulate new Jaccard‐type or Sørensen‐type indices based on species abundance data. We then propose estimators for these indices that include the effect of unseen shared species, based on either (replicated) incidence‐ or abundance‐based sample data. In sampling simulations, these new estimators prove to be considerably less biased than classic indices when a substantial proportion of species are missing from samples. Based on species‐rich empirical datasets, we show how incorporating the effect of unseen shared species not only increases accuracy but also can change the interpretation of results.     

Terrestrial birds as indicators of agricultural-induced changes and associated loss in conservation value of Mediterranean wetlands

During the last decades, agricultural intensification has modified the hydrology of Mediterranean wetlands, as has occurred in the Mar Menor coastal lagoon (SE Spain). Salt-steppe dominated wetlands, characteristic of transitional areas surrounding this lagoon and rich in biodiversity values, are threatened by changes in their water regime originated by land-use changes in the watershed. Traditional dryland cultures have also been replaced by irrigated ones. We assess the direct and indirect changes induced by agriculture on a terrestrial vertebrate community (steppe birds) especially sensitive to these ecosystem changes. This is made on the basis of several surveys of terrestrial birds (excluding aerial feeders and raptors) carried out between 1984 and 2008 in a representative wetland of the lagoon's continental margin (Marina del Carmolí). The changes in this bird assemblage reflect the hydrological modifications induced by agriculture at the watershed scale, which have significant effects on the relative representation of wetland habitats. Bird metrics and indices (species abundance, taxonomic composition, conservation value) describe these community changes as the combination of early declines in some species and families, and transient or late increases in other. In the long term, the family Alaudidae (and particularly species like Melanocorypha calandra) have lost importance to the benefit of Turdidae and Fringillidae. The area of salt-steppe explains a large part of the variation in the abundance of Alaudidae, while most variation of Turdidae and Fringillidae respond to the area of saltmarsh. Some Alaudidae seem to take advantage of the intermediate stages of saltmarsh expansion (Calandrella rufescens), or from the marginal irrigated crops fringing the wetland (Calandrella brachydactyla) that could compensate the loss of original agricultural habitats. Habitat changes in the wetland have occurred in three differentiated stages, and modify the steppe bird community towards a more heterogeneous assemblage including scrubland and palustrine species. Among three indices of ornithological value, only that based on the EU Bird's Directive Annex I species was negatively affected, but since the wetland has been designated a Specially Protected Area under this regulation, this represents a management failure. There exists some chance, however, to manage peripheral cropland in favour of biodiversity. The importance of monitoring in conservation evaluation and management is also stressed, since the terrestrial bird community of this wetland has not been regularly surveyed. In fact, its evaluation against the Bird's Directive criteria was made in a period of quick departure from the original, good ecological state of the wetland.     

Trends in estuarine fish assemblages facing different environmental conditions: combining diversity with functional attributes

Changes in the Mondego estuary (Portugal) fish assemblage were documented with a long-term monitoring program between June 2003 and March 2010, during which several extreme environmental events occurred, including severe droughts and heavy precipitation. The structure and composition of the fish assemblage was analyzed based on a set of indicators: dominance, diversity, evenness, and composition in functional groups (ecological and feeding guilds). Higher species number, diversity, and evenness were observed in the dry periods. Variations in the relative abundance of the ecological guilds were also observed: in dry years, estuarine residents were the most abundant group, while in typical and rainy years, the marine estuarine-dependent species increased in abundance. Among the feeding guilds, the most abundant group was the invertebrate and fish feeders. Planktivorous and invertebrate feeders occurred in higher abundance in dry years, while the opposite was verified for omnivorous species. The mean trophic level of the fish assemblage increased during the drought period, constantly decreasing afterward, which could be attributed to an increase in predators in dry years. The cumulative responses of estuarine fish assemblages to ongoing climate changes and discrete extreme weather events confirm their importance as indicators of environmental changes.     

Changing approaches to monitoring during the period of the ‘Use of Algae for Monitoring Rivers’ symposia

The literature on monitoring rivers using benthic algal communities is reviewed, especially that for Europe during the past 20 years. In particular, papers in a series of symposia at approximately 3-year intervals are considered to assess the extent to which aims and methods have shifted. A variety of methods were being tested in the early 1990s, and some put to practical use. However, the requirements of the EU Urban Waste Water Directive in 1991 have gradually narrowed procedures in most countries outside Scandinavia to the use of indices based on benthic diatoms to monitoring nutrients, especially phosphate. Most countries in Europe now adopt one of a few indices. The same indices are being used to deal with the requirements of the EU Water Framework Directive introduced in 2000 to achieve good ecological status by 2015. It is argued, however, that features of upland river sites require the development of revised indices for this purpose. Features of many sites include highly variable nutrient concentrations and ratios, and the greater importance of organic phosphate. Two possible approaches are suggested to developing a revised index. One is a diatom index which incorporates information about the environmental features important here. The other is to use an index which incorporates data on genera from all algal phyla, with emphasis on those which are long-lived.     

Ability of invertebrate indices to assess ecological condition on intertidal rocky shores

The implementation of directives such as the European Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) has promoted the development of several tools and methods for assessing the ecological health of marine ecosystems. Within the scope of the WFD and in terms of rocky shores, several multimetric tools were developed based on the macroalgae biological quality element (BQE), in addition to those based on macroinvertebrates.The WFD requires member states to assess each BQE separately. The present work aimed to test the ability of ecological indices to distinguish sites within anthropogenic disturbance gradients caused by organic enrichment, using macroinvertebrate communities on intertidal rocky shores. Owing to the lack of more specific indices (for rocky shore), indices based on abundance, diversity and/or taxonomic composition were selected from several widely used indices in ecological studies and/or developed for soft-bottom macroinvertebrate communities.Present findings reveal several indices based on diversity and/or taxonomic composition able to distinguish sites within the disturbance gradients, showing increasing quality from the site nearest the source of organic enrichment to that farthest from it, especially indices calculated using biomass data, and in the summer season. Such results open good perspectives for the use of intertidal macroinvertebrate communities from rocky shores, and also help add the perspective of this biological quality element in the ecological quality assessment of coastal waters.     

Performance of two southern california benthic community condition indices using species abundance and presence-only data: relevance to DNA barcoding

DNA barcoding, as it is currently employed, enhances use of marine benthic macrofauna as environmental condition indicators by improving the speed and accuracy of the underlying taxonomic identifications. The next generation of barcoding applications, processing bulk environmental samples, will likely only provide presence information. However, macrofauna indices presently used to interpret these data are based on species abundances. To assess the importance of this difference, we evaluated the performance of the Southern California Benthic Response Index (BRI) and the AZTI Marine Biotic Index (AMBI) when species abundance data were removed from their calculation. Presence only versions of these two indices were created by eliminating abundance weighting while preserving species identity. Associations between the presence and abundance BRI, and the presence and abundance AMBI were highly significant, with correlation coefficients of 0.99 and 0.81, respectively. The presence versions validated almost equally to the abundance-based indices when applied to the spatial and the temporal monitoring data used to validate the original indices. Simulations in which taxa were systematically removed from calculation of the indices were also conducted to assess how large the barcode library must be for the indices to be effective. Correlation between the BRI-P and BRI remained above 0.9 with only 370 species in the library and reducing the number of species to 450 had almost no effect on correlation between the presence and abundance versions of the AMBI.     

On the use of sample indices to reflect changes in benthic fauna biodiversity

This paper focuses on the difference between the value of some commonly used diversity indices (Simpson, Shannon, abundance, richness) calculated from benthic grab samples and their value in the population or region from which the samples are taken. The ability of the sample indices, as well as a recently derived relative Shannon index, to reflect change in biodiversity is examined in a short simulation study based on changing one of the diversity parameters (abundance, richness and evenness) in the population, whilst keeping the other two components constant. Our results suggest that, whilst their population equivalents do not always reflect biodiversity changes, the sample Simpson, Shannon and Richness indices perform well. We note that this will be true for any surveys where the sampling programme fails to detect many species in a population, and hence will be applicable for most benthic surveys. The use of sample indices to detect changes in biodiversity from long-running time series in the Thames and Tyne estuaries is illustrated.