Cyanobacteria dominance drives zooplankton functional dispersion

Abstract

Accelerated eutrophication reduces water quality and shifts plankton communities. However, its effects on the aquatic food web and ecosystem functions remain poorly understood. Within this context, functional ecology can provide valuable links relating community traits to ecosystem functioning. In this study, we assessed the effects of eutrophication and cyanobacteria blooms on zooplankton functional diversity in a tropical hypereutrophic lake. Phytoplankton and zooplankton communities and limnological characteristics of a tropical Brazilian Lake (Southeast, Brazil) were monitored monthly from April 2013 to October 2014. Lake eutrophication indicators were total phosphorus, total chlorophyll-a, and chlorophyll-a per group (blue, green, and brown). The variation of major phytoplankton taxonomic group biomass was calculated and used as a proxy for changes in phytoplankton composition. Zooplankton functional diversity was assessed through functional dispersion and the community-weighted mean trait value. Regressions were performed between the lake eutrophication indicators, the phytoplankton biomass variation, and zooplankton functional dispersion. Our results suggest that eutrophication and cyanobacterial dominance change the composition of zooplankton traits and reduce functional dispersion, leading to zooplankton niche overlap. These findings are important because they provide a meaningful view of phytoplankton-zooplankton trophic interactions and contribute to an improved understanding their functional effects on aquatic ecosystems.