Spatio-temporal variation of microcystins and its relationship to biotic and abiotic factors in Hongze Lake, China

An investigation of three particle-associated microcystin (MC) congeners (MC-LR, MC-RR, and MC-YR) was performed in 2013 from August to November in Hongze Lake, China. All MCs congeners exhibited significant spatial and temporal variability. Particle-associated MCs were commonly found in this lake, but MC-LR was present at low levels (0.075-1.252 μg/L). All three MC congeners were found to be significantly correlated with non-toxic phytoplankton (e.g., chlorophyte, cryptophyte and diatoms), while only MC-YR and total MC were correlated with cyanobacteria biomass. Copepods, rotifers and three genera of Cladocera were positively correlated with MC concentrations, but feeding habits of these zooplankton species might have different effects on different MC congeners and total MC distributions. Linear mixed effects (LME) model results showed that the interactions between cyanobacteria and other non-toxic phytoplankton or zooplankton species may drive MCs dynamics. Physiochemical parameters also may affect MC congener variability individually or through their effects on toxic cyanobacteria. The results of this study suggested that MCs distribution in Hongze Lake was site-specific and could be influenced by biotic and abiotic factors both individually and through their interactions.