<p>The quantity and quality of plankton are generally affected by the characteristics of the water, and water environmental conditions are also considered key factors affecting the growth of hydrobionts. Consequently, an investigation was conducted into the environmental parameters, and the characteristics of plankton in the sampling sites of Mazuao, Sanggou Bay, and Guazichang, as well as their impact on the growth parameters of oysters. The results indicated that the average water temperature in the Mazuao area was higher than that in Sanggou Bay and Guazichang, while the salinity was lower. The dissolved oxygen and pH values in all three areas met the criteria for mariculture water quality. The diversity and abundance of plankton exhibited seasonal variations, with the total abundance being higher in June (summer) and reaching the minimum in December (winter) in all three sea areas. The phytoplankton species composition in the three aquaculture areas was of the ‘Diatom-Pyrrophyta’ type, and diatoms dominate in plankton. Redundancy analysis (RDA) showed that plankton abundance has the highest correlation with water temperature, salinity, dissolved oxygen and pH. Notably, the Mazuao area had the highest average total abundance of phytoplankton throughout the year. Overall, oysters could obtain better growth advantages in the Mazuao area. RDA indicated that water temperature and plankton abundance in the Mazuao area were dominant factors affecting the growth parameters of oysters. Understanding these relationships is crucial for effective coastal ecosystem management and ensuring the long-term sustainability of aquaculture industries.</p>