The relationship between littoral benthic invertebrates and lakeshore modification pressure in two alpine lakes

Lakeshore modifications influence littoral communities but little is known about their impacts on littoral benthic invertebrates. We studied the relationship between littoral benthic invertebrates and lakeshore modifications in two alpine lakes differing in naturalness and trophic status. Benthic invertebrates were sampled using a multihabitat sampling approach. The lakeshore modification pressure was described by five Slovenian Lakeshore Modification index (LM) classes. A three-way PERMANOVA revealed significant differences in littoral invertebrate assemblages between the lakes and among the LM classes as well as among the sampling years, albeit in the latter case the explanatory power was low. An investigation of benthic invertebrate metrics revealed that several were at least moderately correlated with LM classes (Spearman rho > 0.5). The metrics either showing the best response to the lakeshore modification and/or being commonly used metrics in the bioassessment of European lakes were selected for additional analysis. Thus, a maximum of six metrics per metric group (compositional/abundance, functional, richness/diversity and sensitivity/tolerance) were plotted against the LM classes and further analysed in the between-lake comparison. The best-performing metrics were those of the richness/diversity group (Number of Taxa, Number of Families and Margalef diversity index) and the sensitivity/tolerance group (Littoral Fauna Index, Biological Monitoring Working Party). In addition, a between-lake metric comparison revealed that <50 % of the selected metrics showed a significant difference between the lakes. Our results indicate the robustness of certain metrics showing an evident response to lakeshore modification, as littoral benthic invertebrates collected using a multihabitat sampling scheme indicate lakeshore alterations in two subalpine Slovenian lakes.