Ecological Studies On Microcystins In Lakes Chaohu And Taihu

This thesis described field studies on spatial and temporal variation of the hepatotoxic microcystins in two large shallow lakes with dense occurrence of cyanobacterial blooms. Major results and conclusions are listed as follows:1. In Lake Chaohu, microcystin was detected by HPLC in the water sample from all sites on Aug 2002. The maximum MC content was less than 6μg/L. MC concentration was correlated with water tropical status and the biomass of cyanobacteria. There was a remarkable diel variation in microcystin concentration (0.2～3.5μg/L) with the maximum at 15:00. MC-RR concentration was negatively correlated with ammonium (NH₄-N), while MC-LR concentration was significantly correlated with orthophosphate (PO₄-P) and total dissolved phosphorus (TDP).2. In Lake Chaohu, microcystins were detected monthly at seven stations from August 2002 to July 2003. Microcystin concentrations in the water samples varied temporally and spatially from undetectable content to 17.29μg L^-1. MC concentration was correlated with dissolved oxygen, TN, NO3-N, TDN, and water temperature in western basin and with conductivity, water temperature, TP in eastern basin. MC-LR was the dominant variants when TP was relatively low, while MC-RR dominated when total phosphorus concentrations were relatively higher in both basins. It appears...