Abstract:

Population dynamics of Skeletonema costatum from July 1997 to June 1998 at the Daya Bay, Guangdong Province was investigated. The influence of environmental factors on the temporal and spatial distribution of S. costatum was also ana-lyzed. Results showed that S. costatum existed all year round with two cell density peaks in spring and autumn (cell density in autumn was higher than that in spring). In general, cell density of S. costatum in the surface water was higher than that in the bottom water at the Daya Bay. Cell density varied spatially among the sampling stations, showing a trend that cell density in the near-shore aquaculture area and living area was higher than that in the off-shore area from April to June of 1998. The en-vironmental conditions for high-frequency and high-density S. costatum were temperature 25.0?26.0℃, salinity 30.6‰?  31.6‰, DIN (dissolved inorganic nitrogen) 9.2?78.3µg•L?1, DIP (dissolved inorganic phosphorus) 3.7?5.9µg•L?1, and  SiO32?-Si 564.0?1054.6µg•L?1. Correlation analysis indicated that SiO32?-Si, DIN, COD (chemical oxygen demand), and ratio of N to P were the major environmental factors controlling the cell density of S. costatum. In addition, temperature and DO(dissolved oxygen) also affected the growth of S. costatum to some extent.

Key words: Daya Bay, Guangdong Province, Skeletonema costatum, environmental factors, correlation analysis