Study on planktonic copepods ecology in the Pearl River estuary

Based on the data obtained from 12 cruises from 2002 to 2003 in the Pearl River estuary, species composition, dominant species succession, abundance variations and environmental factors influence on planktonic copepods were examined. The Pearl River estuary can be divided into three regions according to its surface salinity, region I(salinity25), region II(salinity from 25 to 30) and region III(salinity30). Results showed that total 65 species were identified. The number of zooplankton species was higher in regions II and III than that in region I. The average abundance of copepods in the Pearl River estuary was 118 ind·m-3. It was higher in regions II (165 ind·m-3) and I (129 ind·m-3) than that in region III (62 ind·m-3), and it was also higher in spring and summer than that in winter. Dominant species presented obvious regional and temporal patterns. Another result from 9 cruises carried out in region I showed that copepods abundance differed monthly and generally increased from the inner to the outer of the estuary. Salinity was an important factor influencing species composition, distribution and abundance of copepods in the Pearl River estuary.