Effects of shoreline alteration and habitat heterogeneity on macroinvertebrate community composition across European lakes

Abstract Human lake shore alterationsoften result in a substantial decrease of littoral and riparian habitat diversity and physical complexity, but the intensity at which shore alterationsaffect biodiversity may differ among European geographical regions. We tested if the response of littoral macroinvertebrate communities to human shoreline alterationsis consistent among geographical regions. We compared community composition and diversity of human alteredwith those of unmodified littoral zonesfrom 51 lakes across seven European countries in four geographical regions based on pooled composite as well as habitat-specific macroinvertebrate samples. Taxonrichness and community composition differed among shoretypes and different habitats in all geographic regions, with morphological alterationhaving an overall negative effect on macroinvertebrate taxonrichness. In addition, habitat heterogeneity also had a strong effect on littoral communities, with highest taxonrichness found in the structurally complex macrophytehabitats in all regions. Average proportional densities of Diptera and Oligochaeta taxa generally increased in morphologically altered shoresin all geographical regions, while Bivalvia, Crustacea, Ephemeroptera, Gastropodaand Trichoptera showed comparatively lower numbers in many anthropogenically alteredsites. Furthermore, taxonrichness was positively correlated with habitat diversity. We were able to relate changes in littoral communities to anthropogenic shoreline alterations, and linked the effect to the loss of habitats and habitat complexity. The results of our study demonstrate that littoral macroinvertebrates respond consistently negative to the influence of morphological alterationsacross European geographical regions in terms of biodiversity. While macroinvertebrates have previously been identified to be useful descriptors of morphological change in single countries/regions, we can now validate that they can be used to assess the ecological status of lakes in terms of morphological alterationsacross European regions. Our results can be used to further improve ealready existing WFD-compliant multimetric indices, for example by including taxa groups, which show a strong reaction to shoreline alterations. This could be supported by the inclusion of a suit of indicator taxa reflecting the loss of complex habitats such as macrophytesin the lake littoral.