Littoral macrobenthic invertebrates of two high-altitude lakes in the Alps: A small-scale analysis

High-altitude lakes have been studied intensively over the last decades both in terms of their biota and general physicochemical patterns and the importance of detailed knowledge of the small scale-regional fauna was underlined. In the present study the littoral macrobenthic invertebrate communities of two alpine lakes placed in the same geographical context (Upper and Lower Balma Lakes, Cottian Alps, Italy) were seasonally characterized, and the observed diversity was investigated in relation to site-specific abiotic features. During the ice-free period, two seasonal sampling campaigns (summer and autumn) were carried out at each lake along the littoral zones: macrobenthic invertebrate were collected and abiotic features (main physicochemical water parameters and main substrates) were monitored. PERMANOVA test disclosed significant differences in the invertebrate assemblages between the lakes, and SIMPER test highlighted that the observed dissimilarity was mainly related to Oligochaeta and Chironomidae taxa. The application of the RDA and VPA showed that differences were mainly due to littoral substrate composition and nutrient concentrations (i.e., phosphorus and nitrates) which could heavily affect both the structures and densities of the macrobenthic invertebrate communities in these environments. Findings from this study improve the knowledge about the macrobenthic invertebrate assemblages in the western area of the European Alps, highlighting the role of site-specific factors in small scales studies, and the importance of detailed knowledge of their local variability. The better understanding of the variation patterns in regional/ subregional biodiversity and their drivers are of pivotal importance and have implications in the decision of conservation policies.