Seasonal ecological study on Chaetoceros community in Zhelin Bay, South China Sea, where have been frequently hit by harmful algae blooms, was performed during 2004-05-2005-02. A total of 72 phytoplankton samples were collected in the present study, and among which Chaetoceros was found to be present in 68 samples, with total 54 Chaetoceros species; main species include: C. affinis,C. brevis,C. castracanei,C. crinitus,C. curvisetus,C. danicus,C. debilis,C. diadema,C. didymus,C. distans,C. laciniosus,C. laevis,C. lorenzianus,C. minutissimus,C. muelleri,C. neocompactum,C. peruvianus,C. pseudocrinitus,C. pseudocurvisetus,C. siamense,C. socialis,C. tortissimus, among which C. debilis, C. didymus, C. lorenzianus, C. minutissimus, C. socialis were the species appeared in Zhelin Bay all year round. The community density ranged from 0 to 23.39×104cells/L and an overall average of 3.55×104cells/L, contributing 290% to total phytoplankton density.
Spatially, Chaetoceros species richness ranged from 0 to 36, and the total density ranged from 0.71-10.24×104cells/L, both were characterized by a typical progressively increasing pattern with the lowest located inner and highest located outer of the bay. Temporally, Chaetoceros species richness ranged from 7 to 46, and the total density ranged from 0.04-7.86 104cells/L, both were characterized by a typical annual pattern with the lowest in cold seasons and highest in warm seasons.
In total, Zhelin Bay had high Chaetoceros species richness and relatively low density. Our analysis indicated that water temperature was the key factor affected the seasonal variation of species richness and density of Chaetoceros, and light、interspecific competition and structure of zooplankton community were important factors affected the spatial and temporal distribution of Chaetoceros.