Resilience of alpine lake macroinvertebrate communities to climate change: a view from the South Carpathian Mountains

Remote mountain lakes experience accelerating ecological change worldwide due to the ongoing warming. In this study, we analyze two alpine lakes, Lake Ana (1940 m) and Lake Peleaga (2122 m), from the Retezat National Park in Romania. The sediment cores cover similar to 400 years, and our aim is to reconstruct critical transitions, the rate of ecosystem change and its driving factors. The extent of human disturbance is weak at these lakes today. Therefore, we assumed the principal role of summer warming in potential ecosystem reorganizations. For verifying this assumption, we use a multi-proxy approach including Pb-210/Cs-137 dating, chironomid, pollen, Cladocera analyses, SPDU, element concentration, organic matter, total nitrogen, C/N ratio and delta N-15 measurements, chord-distance-analysis (RoC) and chironomid-based temperature reconstruction. The assemblages indicated cold, oligotrophic environment and remained relatively stable despite climate change and human pressure, in contrast to assemblages studied from higher altitude (> 2300 m) lakes in the Alps. Our temperature reconstructions show warming from the 2000's, but the results are influenced by fish introduction in the 1990s. We conclude that chironomid communities have not yet passed critical thresholds; the fauna reacted with restrained alterations, which is exceptional in the region, and highlight the importance of altitude and environmental protection.