Original paper

Cyanobacteria alter competitive outcomes between Daphnia and Bosmina in dependence on environmental conditions

Jiang, Xiaodong; Yang, Wei; Xiang, Xingyu; Niu, Yanning; Chen, Liqiao; Zhang, Jiahuan


Cyanobacterial blooms have deleterious consequences in aquatic ecosystems. Using 40-day incubation experiments, the effects of toxic cyanobacteria on cladoceran competition were investigated under various conditions, including phytoplankton composition and quantity, initial colonizing densities of competitors, and water temperature. Although the large-bodied cladoceran Daphnia pulex outcompeted the small-bodied species Bosmina longirostris, the competitive outcome was reversed by the presence of the toxic cyanobacterium Microcystis aeruginosa and became more pronounced with increasing M. aeruginosa concentrations. When the nutritious green alga Chlorella pyrenoidosa was plentiful in diets, D. pulex significantly suppressed B. longirostris and competitive dominance reversal by M. aeruginosa was minimal. In contrast, the reversal was obvious when C. pyrenoidosa was scarce. An increase in the initial number of D. pulex retarded the reversal by M. aeruginosa. Water temperature significantly interacted with M. aeruginosa to alter the competitive outcomes. The reversal of competitive dominance from D. pulex to B. longirostris was more pronounced at 28 °C than that at 20 °C. These results suggest that previous studies using non-interactive populations may not have adequately clarified cyanobacterial influences on zooplankton and that the cyanobacterial shifts on cladoceran competition were affected by the initial conditions.


cladoceranscompetitioncyanobacteriamicrocystis aeruginosazooplankton