Large-scale field evidence on the enhancement of small-sized cladocerans by Microcystis blooms in Lake Taihu, China

To assess the effect of Microcystis blooms on the crustacean zooplankton community, we conducted a large-scale monthly survey from 2008 to 2010 in Lake Taihu, China. During the sampling period, Microcystis was the dominant genus in the phytoplankton community (79 of total biomass), while the crustacean zooplankton community was dominated by small-sized cladocerans (primarily Bosmina coregoni and Ceriodaphnia cornuta) and copepods. During the study, plankton exhibited significant spatial heterogeneity. The northern and western regions suffered from harmful Microcystis blooms and had higher cladoceran production. In the eastern region where Microcystis blooms seldom occurred, copepods accounted for a relatively larger proportion. Both stepwise multiple linear regression and redundancy analysis demonstrated that Microcystis was the most important factor controlling the spatial dynamics of zooplankton. Linear regression analysis revealed that both cladocera and copepoda were positively correlated with Microcystis and the response of cladocerans (R-2 0.73, P 0.001) to Microcystis was stronger than that of copepods (R-2 0.44, P 0.001). Our study suggested that cyanobacterial blooms may change competitive relations of small-sized cladocerans and copepoda, favoring small cladocerans (except larger genera).