Variations in zooplankton functional groups density in freshwater ecosystems exposed to cyanobacterial blooms.

Abstract The recently observed decline of biodiversity has become a major problem on Earth. Anthropogenically-driven climate change and eutrophication of natural habitats represent great threats to both terrestrial and aquatic ecosystems. Particularly vulnerable are freshwater ecosystems, where the mentioned changes promote development of cyanobacteria. Extension of the cyanobacterial bloom period, increase of cyanobacterial biomass production and toxicity may involve numerous changes in freshwater ecosystem functioning. We conducted a study in water bodies exposed to cyanobacterial blooms of different duration: short-lasting and long-lasting cyanobacterial blooms. We tested the impact of cyanobacterial biomass on densities of zooplankton species grouped into functional groups (functional groups densities) under conditions of different bloom length periods. The functional groups of zooplankton were identified on the basis of three functional traits of each species: mean body length (BL), potential food source (FS) and feeding type (FT). The results of the study showed that assembling species into functional groups may be helpful in understanding the interactions between biotic components of ecosystem. The results showed that the response of each functional group density for cyanobacterial biomass development depends on the functional traits of the animals (i.e. how the species interact with the whole food web) and may be different depending on the bloom intensity, which acts like a factor selecting adapted species.