Regional Mountain Conference

High-altitude lakes have been identified as sentinels of global change, acting as early warning systems. Their characteristics make them extremely vulnerable to environmental changes driven by human activity, and, in this sense, they constitute good models for detecting and analyzing the effects of global changes. Although they are generally perceived as pristine, alpine lakes are threatened by air pollution and are highly vulnerable to climate change. The BioAlpine project aims to better understand the links between global changes, biodiversity structure, and alterations in ecosystem functioning and services in high-altitude lakes of the Alps. In particular, the project aims to know: (i) if there are differences in the food web’s structure and in the transfer of organic matter among alpine lakes, especially in relation to phytoplankton composition; (ii) if there are variations of atmospheric contaminants (N, P, metallic pollutants, organic pollutants) in lakes with different characteristics (location, depth, watershed size); (iii) if there is a link between the food web structure and the bioaccumulation of pollutants in higher trophic levels (fishes). In total, eight high-altitude lakes with different characteristics, distributed along a longitudinal gradient, will be sampled in 2025 and 2026 in the French Alps. Sampling will be carried out over three campaigns, winter, spring, and late summer, to provide a complete description of lake functioning. Here, we present the first results of the project, focusing on phytoplankton community structure and composition.