Abstract:A phytoplankton and water quality survey was conducted in flood and dry seasons in 2000 in 19 typical reservoirs in Guangdong Province, China, in order to evaluate the trophic state and blue-green algae (cyanophyty) pollution. Results showed that many reservoirs were polluted by blue-green algae, of which the potentially toxic Microcystis was the dominant species and often took up over 50% of the total phytoplankton cell concentration. Cell density and percentage proportion of blue-green algae were 0.1×104-6728.4×104 cells L-1 and 0.53%-99.2%, respectively. Furthermore, species richness and density of blue-green algae were closely related to the water quality. Results based on phytoplankton community structure and trophic state index(TSI) revealed that the trophic level was lower in reservoirs located at upper reaches of rivers and mountainous districts than at lower reaches and coastal regions. Moreover, the water quality of reservoirs in Dongjiang and Beijiang drainage areas were better than those in other water areas especially the west coastal area and the delta area of the Pearl River. Most reservoirs have been polluted to some extent and belonged to mesotrophic state, two in Dongjiang drainage area are oligotrophic, while other three which located in highly economic developing coastal areas are heavily polluted and enriched.
