As seen in Fig. 2, the N. minor exudates also showed an inhibi- tory effect on the natural phytoplankton assemblage with Microcystis sp. being dominating parts of the lake water in a concentration- dependent manner, as indicated by significant decrease of the chlorophyll a and TFP contents with increased N. minor exudate con- centrations (compared with the control groups, p < 0.05). The chlorophyll a contents stand for the phytoplankton biomass, and the TPF contents can reflect the total dehydrogenase activity of the phytoplankton assemblages, and the decrease of chlorophyll a con- tents as well as the total dehydrogenase activity might be a reflection of cell structure and function damage due to N. minor exudate exposure.