Abstract:The growth of the phytoplankton greatly depends on the productivity of the water, and the changes in the water environment can directly determine the community structure of the phytoplankton. Therefore the community structure can serve as an indicator of the productivity and the environment of the water. The recent seawall closing the Funing Bay reclamation project (Fujian Province, China) may have caused lots of changes in the environment and the productivity of the water, however, the reports are lacking. In this study, we collected data about the phytoplankton in the Funing Bay in December of 2011 and in May and August of 2012, and analyzed the seasonal variations in the species composition, the dominant species, the biodiversity and the related factors. There were 149 species identified which belonged to 7 Phylum and 61 Genus. The Phylum including most species was Bacillariophyta followed by Pyrrophyta. The number of observed phytoplankton species was the largest in winter, and the second largest was in spring and followed by summer. There was an obvious seasonal variation in the dominant species. Skeletonema costatum, Cerataulina bergonii, Tribonema affine, Coscinodiscus jonesianus, and Rhizosolenia setigera were the dominant species in winter. In spring, Noctiluca scintillans, Ceratium trichoceros, Nitzschia lorenziana and Pleurosigma aestuarii were the dominant species. Cyclotella striata and Skeletonema costatum were the dominant species in summer. The abundance of the phytoplankton was 0.51×104−1298.73×104 ind/m3, and the average abundance was 137.90×104 ind/m3. The average diversity index was 1.988. The average evenness index was 0.473. The highest diversity index and evenness index were both observed in spring, followed by summer and winter. There was a positive correlation (P<0.05) between active phosphate and the biomass of phytoplankton in winter and summer, but the correlation was negative (P<0.05) in spring. There was also a highly positive correlation between the abundance of the phytoplankton and the chemical oxygen demand (P<0.01). These results suggested that after the seawall was closed, there had been obvious changes in the biomass and the community structure of the phytoplankton in the Funing Bay, and active phosphate was the limiting factor.
