Chlorophyll concentration is an important indicator for characterizing phytoplankton biomass and organic carbon assimilation capacity for photosynthesis. For shellfish farming, chlorophyll concentration can reflect food quantity and quality, and it is also the key factor for the growth of shellfish and control of the maricultural carrying capacity. To understand chlorophyll concentration and spatial distribution in maricultural regions, we need to evaluate the environmental quality and establish a healthy farming mode. Two sampling transects for chlorophyll-a between the inner bay and the mouth of the bay were used, and 4 sampling stations in 4 different maricultural areas were sampled once every 2 h during the day in May 2014 in Sungo Bay. Spatial and diurnal variation characteristics of chlorophyll, as well as the control factors, were analyzed. The results showed that: (1) For the voyage survey, chlorophyll was in the range of 0.11-1.40 μg/L, and the average value was (0.64 ± 0.36) μg/L. The general trend of chlorophyll concentration was higher in the inner rather than the outer site of the bay: shellfish maricultural area > polycultural area > kelp maricultural area > outer site of the bay. Chlorophyll-a concentration was higher in the surface water layer than in the bottom layer in the inner bay, but the reverse trend was observed in the outer bay. (2) The highest chlorophyll concentration was observed in the cage area, with an average value of 1.70 μg/L, and the lowest concentration was observed in the sea grass area (cage area > shellfish area > kelp area > sea grass area). In different farming areas, diurnal variation in chlorophyll a concentration was different, which shows that farming activities may affect chlorophyll concentration. Chlorophyll-a concentration was higher in the surface water layer than in the bottom layer in the sea grass area during the day, but it was the reverse at night. In the cage area, chlorophyll-a concentration was higher in the bottom layer than in the surface layer, regardless of the time; a reverse trend was observed in the shellfish area. However, diurnal variation was complete in the kelp area. (3) There was a significantly positive correlation between chlorophyll-a concentration and temperature or silicate concentration. The linear equation between chlorophyll-a concentration (C₁) in the surface layer and silicate concentration (S₁) or temperature (T) in the lane was as follows: C₁=0.8222 S₁-0.6965 (n=15, P=0.0001, R²=0.6945), C₁=0.1468T-1.4189 (n=15, P=0.0009, R²=0.6462). However, there was no significant correlation with other environmental factors, including ammonia, nitrite, and phosphate. Silicate concentration and temperature may be the main control factors for phytoplankton growth in spring in Sungo Bay. (4) The growth of phytoplankton was limited by multiple factors in Sungo Bay in spring, and there was no significant correlation between chlorophyll-a concentration and nutrient concentrations in the inner bay. Thus, bottom-up forces of nutrients and top-down forces of shellfish feeding can affect the growth of phytoplankton.