Quantitative distribution of pelagic polychaetes in coastal waters of East China Sea and its relations to environment.

Based on the data of four seasons investigations in the coastal waters of the East China Sea (28°00′ N-32°00′N, 122°00′ E-123°30′E) from 2002 to 2003, this paper studied the seasonal characteristics of the changes in total abundance and species of pelagic polychaetes, the relationships between these changes and water masses, the quantitative changes of dominant species and their contribution to polychaetes, and the environmental adaptation of dominant species, with the ecological characteristics of pelagic polychaetes in the outer East China Sea compared. The results showed that the total abundance of pelagic polychaetes in study area had an obvious seasonal change, with the highest average abundance (1.30 ind·m-3) in summer and the lowest (0.04 ind·m-3) in spring. A total of 15 species of pelagic polychaete were identified, and Typhloscolex muelleri, Vanadis sp., Plotohelmis capitata were the dominant species. Among the dominant species, only T. muelleri appeared in four seasons, and its dominance was higher in summer and winter, being 0.16 and 0.1, respectively. Vanadis sp. only appeared in summer, while P. capitata was in autumn. The contribution of T. muelleri was higher in spring and summer, being 1 and 0.94, respectively, which suggested that this species adapted well in warm waters and euryhaline environment. Our study indicated that the complex species composition and the greater spatio-temporal change in species number were the characteristics of pelagic polychaetes in the coastal waters of the East China Sea.