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Morphological alteration of shorelines and eutrophication both affect the biological integrity of European lakes. These pressures, often acting simultaneously, are difficult to tease apart. In this study, we related the number of taxa with specific habitat preference to habitat complexity across lakes of varying nutrient state. Habitat complexity at morphologically altered shorelines was significantly lower than at unaltered sites across trophic categories. A generalised linear mixed-effects model showed decreased number of taxa with specific mesohabitat preference at morphologically simplified sites in oligotrophic and mesotrophic, but not eutrophic lakes. These results suggest: (1) an antagonistic interaction between the effect of nutrient enrichment and morphological alterations on lake littoral communities and (2) the number of macroinvertebrate habitat specialists could potentially be used to assess the effects of structural simplifications of shorelines in lakes of low to medium nutrient status. We conclude that the use of functional traits approach in aquatic ecology should foster better understanding of stressor–response relationships for combined effect of multiple stressors.

Morphological degradation constitutes one of the most severe threats to the ecological integrity of lakes. The development of biotic assessment methods for human lake shore alterations using littor ...

Implementation of the EU Water Framework Directive (WFD) has drawn much attention to hydromorphological alterations of surface waters. The Lake Habitat Survey (LHS) protocol provides a method for characterising and assessing the physical habitats of lakes and reservoirs. Two metrics were developed based on this method: the Lake Habitat Modification Score (LHMS) and the Lake Habitat Quality Assessment (LHQA), as measures of lake modification and habitat value, respectively. However, the use of these metrics to predict measures of ecological quality remains largely untested. Thus, we assessed the relationships between LHS metrics and the littoral macroinvertebrate community in 42 lakes across Europe. A significant relationship was found between littoral macrophyte descriptors and riparian natural land cover variables of the LHQA score and macroinvertebrate community composition in 2 out of 4 European regions. No relationship was found between macroinvertebrate community composition and the LHMS. Some significant correlations were found between selected macroinvertebrate metrics and the LHS scores, but this pattern was not consistent across regions, and no relationship was found with the overall LHMS or LHQA scores. This demonstrates that the LHS metrics do not consistently predict the quality of littoral macroinvertebrate communities across Europe, and a region specific approach may be necessary. However, we could demonstrate a relationship between the site specific LHS variables and the macroinvertebrate community at the site level, and in some cases at the regional level. Therefore, although the LHS metrics do not appear to be a useful for relating habitat quality and pressure to littoral macroinvertebrate communities, selected LHS variables may exhibit stronger relationships with the biota.

Summary: Beta diversity is the compositional heterogeneity of biotic assemblages among sites, and biotic homogenization is the decrease in beta diversity, facilitated by an increase in similarity of biotic communities over time. Environmental harshness decreases the importance of stochastic processes in structuring assemblages, resulting in a homogenization of the biota. We investigated if increasing nutrient enrichment, land-use pressure, and within-lake habitat alteration would decrease the beta diversity of macroinvertebrates in 46 lakes across Europe. Beta diversity was calculated using global multivariate dispersion. We utilized a structural equation modelling approach to account for hierarchical interdependence between potential impacts, that is the direct effects and correlations among the different impacts. We found clear indications that European macroinvertebrate communities are being homogenized by ongoing lake shore development. Increasing land-use pressure in the form of residential and commercial development had a direct negative effect on beta diversity (standardized coefficient = -0·40), as did roadways, albeit indirectly through an increase in engineering structures (standardized coefficient = -0·31). Increasing within-lake silt levels also homogenized macroinvertebrate communities (standardized coefficient = -0·18), independent of near shore land use. Our results indicate the negative effect of both the near shore land-use pressure and the within-lake habitat alteration on macroinvertebrate beta diversity, with significant interactions between these pressures. Habitat protection should take a more holistic approach to assessing lake development pressure, over a range of scales, as a solely site specific approach is not always biologically meaningful. Thus, future management plans should carefully control and mitigate ongoing development pressure if lake ecosystem health and resilience is to be maintained. Synthesis and applications. This study is the first of its kind to demonstrate European-wide homogenization of littoral macroinvertebrate lake communities with increasing habitat alteration and land-use pressure. Significant interactions occur between different habitat scales, with no one scale entirely accounting for the homogenization effect. To avoid further biotic homogenization, development pressure must be carefully managed at multiple scales, and where possible, minimized. This presents a challenge, as globally there is an increasing expansion of the human population and a consequent increase in anthropogenic pressure across all habitats. This study is the first of its kind to demonstrate European-wide homogenization of littoral macroinvertebrate lake communities with increasing habitat alteration and land-use pressure. Significant interactions occur between different habitat scales, with no one scale entirely accounting for the homogenization effect. To avoid further biotic homogenization, development pressure must be carefully managed at multiple scales, and where possible, minimized. This presents a challenge, as globally there is an increasing expansion of the human population and a consequent increase in anthropogenic pressure across all habitats.

This study investigated patterns of nutrient pollution in waterbody types across Greater London. Nitrate and phosphate data were collected by both citizen scientists and professional ecologists and their results were compared. The professional survey comprised 495 randomly selected pond, lake, river, stream and ditch sites. Citizen science survey sites were self-selected and comprised 76 ponds, lakes, rivers and streams. At each site, nutrient concentrations were assessed using field chemistry kits to measure nitrate-N and phosphate-P. The professional and the citizen science datasets both showed that standing waterbodies had significantly lower average nutrient concentrations than running waters. In the professional datasets 46% of ponds and lakes had nutrient levels below the threshold at which biological impairment is likely, whereas only 3% of running waters were unimpaired by nutrients. The citizen science dataset showed the same broad pattern, but there was a trend towards selection of higher quality waterbodies with 77% standing waters and 14% of rivers and streams unimpaired. Waterbody nutrient levels in the professional dataset were broadly correlated with landuse intensity. Rivers and streams had a significantly higher proportion of urban and suburban land cover than other waterbody types. Ponds had higher percentage of semi-natural vegetation within their much smaller catchments. Relationships with land cover and water quality were less apparent in the citizen-collected dataset probably because the areas visited by citizens were less representative of the landscape as whole. The results suggest that standing waterbodies, especially ponds, may represent an important clean water resource within urban areas. Small waterbodies, including ponds, small lakes50ha and ditches, are rarely part of the statutory water quality monitoring programmes and are frequently overlooked. Citizen scientist data have the potential to partly fill this gap if they are co-ordinated to reduce bias in the type and location of the waterbodies selected.

Lake habitat alteration is a major stressor for lakes worldwide, and physical habitat alteration is likely the biggest threat to aquatic ecosystems, exceeding all other anthropogenic pressures. This study sought to elucidate which group of variables was the most important for describing Swedish macroinvertebrate community structure: trophic status, substrate variables or riparian variables. We also investigated what influence each of these groups of variables has on the other. The impact of large scale land use patterns was also investigated, to determine if macroinvertebrates responded differently in two different catchment land use types: impaired and unimpaired. Partial canonical ordination analysis showed that substrate variables were the most important for describing macroinvertebrate community variation in both catchment land use classes, followed by riparian descriptors, with the trophic signal only becoming clear when lakes were more strongly stratified for coarseness of substrate. This trophic effect was only evident in the impaired lakes, as the trophic gradient was much shorter in the lakes with an unimpaired catchment. Our results suggest that trophic effects on benthic invertebrates are nested within substrate habitat effects, and were masked by local habitat heterogeneity. This indicates that, at least in the Swedish situation, greater care needs to be taken in stratifying the substrate sampled in order to see this nutrient pressure-macroinvertebrate response relationship. The macroinvertebrate community composition was also responding to changes in riparian vegetation, specifically the presence of riparian trees and canopy cover. These variables, or lack of, are possible proxies for anthropogenic alteration of lake shores. Therefore, although macroinvertebrates may not be strong indicators of trophic pressure in all cases or habitats, they may be useful indicators for other anthropogenic pressures (e.g. hydromorphology) on lake shores.

1.Lake Habitat Survey (LHS) provides a standard method for characterizing the physical habitat of lakes and reservoirs, but has not been tested for its relevance to the composition and abundance of macroinvertebrates. This study investigated the relationship between the metrics used in LHS and components of macroinvertebrate communities found in the littoral zone of a shallow calcareous lake in the west of Ireland. 2.A scoring system, the Habitat Quality Assessment (HabQA), developed from the Lake Habitat Quality Assessment (LHQA) of the LHS, was used to assess the relationship between habitat quality based on physical structure within 10 LHS ‘habplots’ and metrics of the macroinvertebrate community. 3.Macroinvertebrate taxon richness, both of adults found in the riparian zone and larvae found in the littoral zone, correlated positively with the HabQA score. Macrophytes within the littoral zone, and complexity of riparian vegetation within the riparian zone, were particularly important in driving the HabQA score. While overall abundance of macroinvertebrates did not vary with HabQA score, that of particular genera did. 4.The HabQA score was a useful surrogate of taxon richness for adult and larval aquatic macroinvertebrates, suggesting that, in general, LHS provides a useful conservation assessment tool relevant for macroinvertebrates. However, in some circumstances, such as wave-washed stony substrates devoid of macrophytes, the HabQA score may not capture the quality of a site for macroinvertebrates, and the importance of natural but low diversity sites should not be neglected in conservation assessment of lakes. Similarly, while the LHS method notes the presence of alien species, further work on how these could be incorporated into the method would be useful. 5.Reliance on a single, or overall combined, metric score across quality elements, whether based on biotic or structural assessment, has some potential limitations. It is clear that for conservation management a holistic assessment of naturalness, representativeness and species rarity needs to be made in conjunction with scoring systems. Copyright © 2009 John Wiley & Sons, Ltd.

Besides pollution, lakes are affected by human alterations of lake-shore morphology. However, ecological effects of such alterations have rarely been studied systematically. Hence, we developed tools to assess the ecological effects of anthropogenic morphological alterations on European lake-shores based on pressure-specific response patterns of littoral macroinvertebrate community composition. Littoral invertebrates were sampled from 51 lakes in seven European countries. Sampling covered a range of natural to heavily morphologically degraded sites including natural shorelines, recreational beaches, ripraps and retaining walls. Biological data were supplemented by standardized morphological data that were collected via a Lake Habitat Survey (LHS) protocol and subsequently used to develop a morphological stressor index. Two biotic multimetric indices were developed based on habitat-specific samples (Littoral Invertebrate Multimetric based on HAbitat samples, LIMHA) and composite samples (Littoral Invertebrate Multimetric based on COmposite samples, LIMCO) through correlations with the morphological stressor index. Similarity analyses showed strong spatial differences in macroinvertebrate community composition between four main geographical regions, i.e. Western, Northern, Central and Southern Europe. The morphological stressor index as well as LIMCO and LIMHA have been developed for each geographical region specifically, thereby optimizing correlations of LIMCO and LIMHA with the respective morphological stressor index. The metric composition of LIMCO and LIMHA and their correlation coefficients with the morphological stressor index are comparable to existing national and regional methods that assess morphological lakeshore degradation via macroinvertebrate communities. Hence, LIMCO and LIMHA indices constitute a new stressor-specific assessment tool that enables comparable lake morphology assessment across Europe, as it has been developed involving a uniform methodology followed by regionalized optimization. These tools fulfil the standards of the EU Water Framework Directive and thus may complement existing assessment approaches used in lake monitoring focusing solely on lake eutrophication so far.