Short-term responses of phytoplankton to nutrient enrichment and planktivorous fish predation in a temperate South American mesotrophic reservoir

Abstract

Top-down and bottom-up mechanisms have been proposed as potential regulators of the phytoplankton biomass of aquatic ecosystems. We evaluated the effect of nutrient enrichment and planktivorous fish predation through a mesocosm experiment conducted at a polimictic system (Penuelas reservoir, Chile). Results show that phytoplankton biomass increased, while diversity decreased, in nutrient-enriched treatments. Planktivorous fish predation did not have a significant effect on phytoplankton biomass but led to a reduction of bigger zooplankton abundance. These results are an indication that these reservoir systems would be preferentially influenced by resource availability in short-term manipulations.