Spatial distribution and seasonal variation of macrobenthos in intertidal flat of Sheyang estuary,Yancheng Nature Reserve

From November 2008 to October 2009,the macrobenthic community in the intertidal flat of Sheyang estuary,Yancheng Nature Reserve was sampled monthly. A total of 16 species belonging to 15 families,4 classes,and 3 phyla were collected,which were mollusks,crustaceans,and polychaetes. The species number found at 4 sampling sites (intertidal zone with Spartina alterniflora,and high,middle,and low tidal flats without plants) was 6,7,13,and 7,respectively. Two-factor ANOVA was used to analyze the effects of sampling site and season on the species number,density,and biomass of macrobenthic community,and the biodiversity indices (Margalef,S; Shannon,H; Pielou,J; and Simpson,D). There were significant differences in the species number (P0.01),density (P0.01),and biomass (P0.01) among sampling sites,but less difference was observed among seasons. The H (P0.01),D (P0.05),and S (P0.05) were all significantly affected by sampling site but less affected by season,while the J was less affected either by sampling site or by season. The hierarchical clustering of between-groups linkage and the non-matric multi-dimensional scaling showed that the macrobenthic community in high and middle tidal flats without plants had no distinct dividing line,while that in intertidal zone with S. alterniflora and in low tidal flat without plants was in adverse. Our results revealed that,comparing with seasonal variation,habitat difference was much more important for the difference in the macrobenthic community composition in intertidal flat.