Interactions of Cyanobacteria and Aquatic Organisms: Can Crustaceans Facilitate Cyanobacteria Bloom?

— Changes in the abundance, biomass, and species composition of cyanobacteria, as well as the composition and amount of produced toxins were studied in three types of model communities: at low (1 mg/L) and high biomass (12 mg/L) of planktonic crustaceans and in the presence of nektobenthic amphipods Gammarus pulex (1.4 mg/L) at low zooplankton biomass. Experimentally, more intensive development of cyanobacteria, an increase in their share in phytoplankton, and longer bloom were observed at high biomass of crustaceans. In microcosms with a high abundance of planktonic cladocerans ( Daphnia longispina ) and copepods ( Eudiaptomus ), the highest amount of microcystins in water was noted (including up to 536 ng/L of the most toxic form, microcystin LR). The influence of crustaceans on cyanobacteria was associated with their active excretion of biogenic substances (first of all, phosphates).