Community Structure of Macrobenthos in Laizhou Bay and Adjacent Waters

A quantitative survey on macrobenthos was carried out at 25 sampling stations in Laizhou Bay and adjacent central Bohai Sea waters in November 2006.Multivariate statistical procedures included in PRIMER were used to investigate the community structure and to elucidate the relationship between community structure and environment variables in the study waters.Results suggested that two macrobenthic communities with different faunal and species composition could be recognized.The one located in central Bohai Sea was represented by Ringicula(Ringicula) doliaris,Kellia porculus,Sternaspis scutata and Eriopisella sechellensis.The other in Laizhou Bay was characterized by Nitidotellina minuta,Cythura sp.,Corophium sinense and Sternaspis scutata.The three stations located outside of the Huanghe River Estuary in the west of the bay formed a sub-group within the major Laizhou Bay group and was dominated by Sthenolepis japonica,Amphioplus japonicus,Theora lata and Iphinoe tenera.Difference in community structure could be best explained by water depth,bottom salinity and other factors in the bottom water,but was also correlated with sediment chlorophyll a content and heterogeneity.Pelagic environment in the study waters was primarily related with water depth and distance to the coast.Sedimentary environment,especially sediment composition was primarily influenced by Huanghe River,with an increasing particle size and heterogeneity and decreasing silt-clay from the west to the east.Sedimentary environmental gradient and its influence on faunal structure were more apparent in Laizhou Bay than that in central Bohai Sea.Compared with 1980s and 1990s,species composition and community structure of macrobenthos in the study waters have been changing in a general direction towards more small polychaetes and crustaceans and less large-sized species of echinoderms and bivalve mollusks.