Cladocera in shallow lakes from the Ecuadorian Andes show little response to recent climate change

Abstract

Lakes of the Andean paramo are critical water reservoirs for millions of people. Paramo ecosystems have experienced anthropogenic warming faster than the global average. Recent paleolimnological work from Cajas National Park (southern Ecuador) revealed striking shifts in diatoms and Cladocera linked to climate change. However, the impacts on shallow lakes (< 5 m deep), which are numerically dominant on the landscape, remain poorly understood. Here, we use paleolimnology to investigate cladoceran species changes and responses to climate change in three shallow waterbodies from Cajas. Each system supported abundant littoral Cladocera. The deepest site (~ 4 m) contained the highest proportion of pelagic taxa, while the shallowest (~ 0.3 m) contained almost exclusively littoral taxa. Cladoceran assemblages in these shallow lakes reflect littoral habitat, likely partly influenced by shifting precipitation, and in one site, construction of a small rock dam. The cladoceran assemblage shifts do not align with regional temperature increases and reduced wind speeds, contrasting the ecological responses previously recorded in nearby deeper lakes. Although these polymictic, ice-free shallow systems are not immune to climate-related change, algal and cladoceran assemblages in nearby deeper lakes are responding earlier and more sensitively to recent climate changes, largely through changes to lake thermal stratification regimes.