[Ecological characteristics of phytoplankton in coastal area of Pearl River estuary].

Five cruises of phytoplankton survey were made in costal area of Pearl River estuary in 1998-1999. The results showed that 239 species were identified, 72.4% of which belonging to Bacillariophyta, 23.8% to Pyrrophyta, and 3.8% to others. The dominant species were warm and eurythermic species Thalassiothrix frauenfeldii, Nitzschia delicatissima, Thalassiothrix frauenfeldii and Thalassiosira subtilis, and changed with an obvious seasonal succession. The cell density ranged from 0.2 x 10(4) to 2,767.1 x 10(4) cell x m(-3), with an average of 98.7 x 10(4) cell x m(-3), and the mean cell density was obviously higher in summer and winter than in spring and autumn. The regional variation revealed that the cell density in shore area was visibly higher than that in offshore area, and the largest density area was at the southeast of Shangchuan Island all the year around. The range of mean Shannon-Wiener index, Pielou evenness index and biodiversity threshold was 2.63-3.17, 0.53-0.71 and 1.74-2.23, respectively. According to the diversity index, it was concluded that the diversity level of phytoplankton community in coastal area of Pearl River estuary was relatively high and stable.