CONICET | Buscador de Institutos y Recursos Humanos

This study aimed to determine the factors affecting plankton structure along a salinity gradient during the summer in high altitude endorheic lakes in Catamarca Province (Argentina). During the summer 2013, eight lakes located between 3,000 and 4,300 meters above sea level were sampled in a seven-day period being analysed plankton, limnological variables and flamingo abundance. PCA analysis explained 80% of the system variability, permitting lakes to be ordered by salinity: subhaline (SH), hypohaline (HH), and mesohaline (MH). A total of 101 phytoplankton taxa were registered, having Bacillariophyceae the highest richness (43 species registered). HH lakes were dominated by Bacillariophyceae (between 65 and 100%), while Chlorophyceae and Euglenophyceae were more abundant in SH and MH lakes. Zooplankton was poorly represented in richness (only 21 species were registered). MH lakes were dominated by Copepoda (>85% of total abundance), and HH lakes by Rotifera (>51% of total abundance). It was not found a clear pattern in SH lakes. The RDA analysis explained 70.7% of phytoplankton variability and 75.7% of zooplankton variability. Bacillariophyceae presence was associated with availability of dissolved silica, while Euglenophyceae and Chlorophyceae were associated with a higher nitrogen:phosphorus ratio. Cladocera and Copepoda abundance was linked to Euglenophyceae abundance and the area of lakes while Rotifera displayed a positive relation with the concentration of dissolved organic matter. We conclude that both phytoplankton and zooplankton abundance are mainly controlled by Bottom-Up forces including dissolved silica for Bacillariophyceae, and availability of Euglenophyceae for zooplankton while salinity has an effect on plankton richness distribution.