Located on Chongming Island,China,Zhongxin Lake serves as a fishing and landscape water body with a total water surface area of 52,000 m2.The Lake is enclosed with little external pollution,which makes it an ideal object to investigate the relationship between hydro-meteorological factors (such as wind,light intensity,temperature,and flow pattern) and phytoplankton biomass.An intensive observation and monitoring program was conducted at six sampling points along five locally connected watercourses of the Lake representing various hydro-meteorological conditions from March to December,2008.Significant spatial variations of phytoplankton biomass were observed which can be explained by the coupled effects of wind driven turbulence and lake morphology.The low level of phytoplankton biomass in the north watercourse was remarkably correlated to the prevailing wind of southeast and northwest.Diatoms preferred in moderate conditions in March and April with the optimum light intensity below 174 μmol/( m2·s).The optimum light intensity for green and blue algae blooming at 22 ℃ and 26 C is below 301 μmol/(m2 · s) and 359 μmol/(m2 · s),respectively.Variation of the dissolved oxygen level also has an effect on the blooming and extinction of phytoplankton.