Glacial-fed and páramo lake ecosystems in the tropical high Andes

The effects of climate change in the tropical Andes are predicted to be devastating. While changes altering hydrology are already occurring, our knowledge of high-altitude lentic ecosystems is limited. Therefore, we carried out a survey of 16 small (0.06–7.1 ha) and shallow (≤ 6.5 m) fishless lakes, above the treeline in the Ecuadorian Andes (≤ 3863 m). Our objectives were (a) to provide baseline data of representative lakes for future monitoring and research and (b) to identify environmental variables driving taxon richness and plankton biomass. We hypothesised that both would decline along the altitudinal gradient. A range of geographical, physical and chemical data and samples of phytoplankton, zooplankton and benthic macrofauna were collected. We found that the lakes are cold, oligotrophic and have a low plankton diversity and biomass. We were able to show that altitude, depth, water chemistry and inflow of glacial meltwater are the most important variables controlling the lake biota. Furthermore, we identified two distinct types of lakes: highly turbid due to glacial runoff and clear watered lakes. These may represent different stages of lake development from newly formed, ultraoligotrophic pro-glacial lakes to oligotrophic páramo lakes.