Ecological characteristics of phytoplankton community from eutrophic waters in the Maluan Bay

The present study is based on the analysis ohthe data collected in 10 cruises during the periods of 2 surveys (from May 1992 to January 1993 and from August 1993 to May 1994).The resulu show that the number of phytoplanktat species in highly eutrophic waters of the Maluan Bay is low,only 6-35 species from each cruise and 66 species in total from the 2 surveys.The phytoplankton abundance is high.The mean cell densities of phytoplankton from the net samples were 21 386×10⁴cells/m³ for the first survey and 110 136×10⁴ cells/m³ for the second survey,that from the water samples was 1 150.7 cells/cm³.The mean concentration of chlorophyll a reached 6.67 mg/m³.Both the species diversity (H') and evenness (J) were low,only 0.78 and 0.28,respectively.The temporal and spatial fluctuation of the cell density of phytoplankton was quite significant,caused mainly by contribution of pennate diatom Nitzschia delicatissima that often abudantly occurred in a closed waters rich in organic matter and could be taken as an mologic indicator of highly eutrophic harbour.The existence of good correlation between the cell density of Nitzxhia delicatissima and some environmental variables (e.g.PO₄^-3-P and COD,etc.),and the heterotrophic tendancy of this species are discussed,too.