Abstract:Two sampling transects for chlorophyll a (Chl.a) between inner bay and the mouth of bay were performed and one sampling station in kelp zone was daily sampled once every 2 hours in May and August,2014 in Sanggou Bay.The spatial distribution and diurnal variation characteristics of Chl.a were studied,and the correlations between Chl.a concentration and physical and chemical factors were analyzed by combining with the environmental factors such as temperature,salt,pH,nutrients and so on in Sanggou Bay,the change of Chl.a and its influencing factor were discussed pre-and-post-the-harvest of kelp in Sanggou Bay.(1) For the voyage survey,Chl.a concentration was significantly higher in summer than in spring in Sanggou Bay.In spring,the average Chl.a concentration in the surface layer and the bottom layer were 0.67±0.39 μg/L,0.50±0.31 μg/L,respectively,and Chl.a concentration was higher in the surface layer than in the bottom layer.The general trend of Chl.a concentration was decreasing from inner bay to the outside of the bay in surface layer in spring.In summer,the average Chl.a concentrations in the surface layer and the bottom layer were 3.39±1.53 μg/L and 3.12±1.43 μg/L,respectively,and Chl.a concentration was higher in the surface layer than in the bottom layer.The kelp area showed the highest values Chl.a concentrations and shellfish area showed the lowest values in the surface layer in summer.The kelp area and shellfish area showed the highest values Chl.a concentrations and outer site of the bay showed the lowest values in the bottom layer in summer.(2) The results of continuous observation showed that Chl.a concentration was in the range of 0.24-0.95 μg/L,and the average value were 0.70 ± 0.19 μg/L in spring in kelp zone.There was less fluctuation for Chl.a concentration day and night in spring.In summer,Chl.a concentration was in the range of 2.01-4.66 μg/L,and the average value were 3.04 ± 0.82 μg/L in kelp zone.There was greater fluctuation for Chl.a concentration day and night in summer.The Chl.a concentration in spring was significantly higher than those in summer.And the nutrient concentration,Si/P,N/P and Si/N ratio in spring were significantly lower than that in the summer.(3) There was a significantly positive correlation between Chl.a concentration and temperature or silicate concentration in the surface layer in spring.And Chl.a was significantly positive correlation with salinity in the bottom layer in summer.The distribution of Chl.a is commonly affected by temperature,silicate,salinity,marine cultures and hydrological environment pre-and-post-the-harvest of kelp in Sanggou Bay.The multi-trophic aquaculture mode of bivalves and seaweeds is important influence factor of Chl.a distribution and variation in Sanggou Bay.