Ecology Study on The Benthic Animals of Pearl River Estuary
珠江口底栖动物生态学研究

Benthic animals collected by grab samples are generally small size and slow activity species. They are usually natural food to fish, shrimp and so on. Pearl River estuary, abundant in fishery resources, is one of the main fishery area in the South China Sea. It has great significance to study the benthic animals in this area. Two cruises for ecological survey of benthic animals at Pearl River estuary were made in Sep. 1999 and April 2000. The sampling stations were presented in Fig. 1. Replicate 0.05m 2 grab samples were collected in each station. A total of 32 species have been identified (15 species in Sep., 21 species in April). The benthic animals were dominated by Potamocorbula laevis (in both seasons) and Owenia fusformis (in spring). The average abundance in terms of individual and biomass are 591.7 ind./m 2 and 26.7 g/m 2 in spring, and 85.0 ind./m 2 and 7.4 g/m 2 in autumn respectively. Mollusca is the majority among the benthic groups, followed by Polychaeta, all the other groups account for less than 5%. The biodiversity, individual abundance and biomass all show an increasing trend from north to south. In addition, comparing with the previous reported data in the recent twenty years, the individual abundance, ranged from 72.4 to 128 ind./m 2, has no significant changes, except for 591.7 ind./m 2 in spring 2000; the biomass, about 10g/m 2, has also no significant changes in spring, except for 27.8g/m 2 in 1991. In autumn, however, the biomass has apparent decreasing trend from 30.1g/m 2 in 1980, 27.8 g/m 2 in 1990, to 7.4 g/m 2 in 2000. Moreover, in terms of the variation of individual abundance and biomass composition, Mollusca is the most abundant by individual abundance, ranged from 22.7%~83.2%, or by biomass, ranged 57.9%~82.5%; Polychaete is the next abundant by individual abundance, made up of 13.4%~52.3%, and all the other groups are minors.