Uncovering aquatic diversity patterns in two Patagonian glacial lakes: does habitat heterogeneity matter?

Abstract

Glacially-influenced lakes are responding to global warming, improving our understanding of these threatened ecosystems is globally imperative especially at southern hemisphere areas like Patagonia. We compared environmental parameters, phytoplankton and littoral benthic macroinvertebrates at two lakes fed by retreating glaciers: El Antiguo (proglacial) and Bagillt (glacial). Our prediction was that differences in water temperature, nutrients, food resources and spatial heterogeneity will modulate aquatic diversity facets. Harsher environmental conditions were recorded at the proglacial lake, including colder water, lower availability of allochthonous resources, and lower pH; but no differences existed in total suspended solids, chlorophyll a, and nutrients. The phytoplankton community (23 taxa) was dominated by Coscinodiscophyceae and Fragilariophyceae at El Antiguo, whereas at Bagillt (20 taxa) Bacillariophyceae and Zygnemathophyceae were the richest groups. The glacial lake included aquatic insects, amphipods, leeches, and mollusks, exhibiting a significantly higher invertebrate richness than the proglacial lake (33 and 8 taxa, respectively). The latter was dominated by Podonominae and Diamesinae (Chironomidae, Diptera). The turnover component of within lakes beta diversity was consistently higher at Bagillt than at El Antiguo. Long-term approaches could clarify whether the expected compositional changes recorded in the northern hemisphere’s aquatic communities correspond to southern hemisphere patterns.