Abstract ID: 3.10287 | Accepted as Talk | Talk/Oral | TBA | TBA

Due to their elevation, catchment characteristics, and simple structure, mountain lakes react sensitively to climate change. However, local topography – one of the prominent features of mountain landscapes – may profoundly affect the climate change signal by reducing the insolation of topographically shaded lakes. Our objective was to quantify the “sun umbrella” effect of local topography on the temperatures and communities of littoral invertebrates of Tatra Mountain lakes (Slovakia). We analyzed data on lake surface water temperature (LSWT) and littoral benthic communities of 18 mountain lakes distributed along a 500-m altitudinal gradient and characterized by differing topographic shading levels: unshaded lakes and shaded lakes (years 2010 – 2011). Further, we compared these temperature data with our recent data from 2021-2023 to address the role of local topography in the modulation of climate change signals on LSWT over time. Shaded lakes were significantly colder and local topography affected the composition of littoral invertebrates. Investigated lake groups supported distinct communities in lower altitudes and shaded lakes were characterized by higher abundances of cold-stenothermal species. However, the community composition of both lake groups converged towards higher altitudes in communities typical for a greater abundance of cold-stenotherms. The proportion of cold-stenothermal species increased with increasing altitude in shaded lakes and was notably greater than that in unshaded lakes along the studied altitudinal gradient. Most of the studied lakes became warmer during ca. 10-year period (on average +0,87°C). Local topography had a marginally significant (p = 0.076) effect on the temperature changes over time. Our results suggest that local topography profoundly affects the temperature and benthic communities of the mountain lakes. Topographically shaded lakes may perhaps provide refuge for cold-stenothermal communities threatened by ongoing global warming. However, the role of local topography in the modulation of climate change signals on mountain lakes requires further research.