Seasonal characteristics of planktonic copepods in 8 estuaries of Pearl River

To study seasonal characteristics of planktonic copepods in 8 estuaries of Pearl River,the investigations in 4 seasons from May 2007 to February 2008 were performed.The species composition,diversity and abundance as well as their relationships with environmental factors in 8 estuaries of Pearl River were studied.Moreover,analysis of the quantitative changes of dominant species and the effects on the total number of planktonic copepods as well as the comparison of planktonic copepods ecological characteristics in the studied waters and controled waters off the Pearl River Estuary were performed.Total of 38 species were identified,among which,Acartiella sinensis,Schmackeria inopinus and Limnoithona sinensis were dominant species and obvious seasonal variations were observed.The average abundance of planktonic copepods of four seasons was 41.83 ind./L,and the highest was in spring(79.06 ind./L),followed by summer(56.11 ind./L) and autumn(17.52 ind./L),winter(14.62 ind./L) was lowest.Species number and diversity index were the highest in summer.Correlation analysis showed that in spring,CODMn had extremely significant impact on the distribution of planktonic copepods in spring,and it is dissolved oxygen and silicate that were the environmental factors which affected significantly the distribution of planktonic copepods in summer and autumn respectively.