Species composition and characteristics of macrobenthic fauna in Daya Bay, South China Sea

Abstract

The species composition,dominance and characteristics of macrobenthic fauna were studied within 124 sampling stations from four survey cruises in Daya Bay,South China Sea,during March,May,September,and December,2008.We found large seasonal changes in macrobenthic faunal community species composition.A total of 279 macrobenthic species were found in Daya Bay in 2008,with an average ratio of species seasonal subroga-tion of 63%.We also observed that the composition of dominant species was relatively stable among seasons,and mainly dominated by a single species.Throughout the year,the most dominant species was Timoclea scabra,fol-lowed by Apionsoma trichocephala,Cerebratulina sp.,Tharyx sp.and Mediomastus sp.The polychaete worms were characteristic macrobenthos in Daya Bay,where they have important ecological functions.It was also evident that the macrobenthic faunal composition in Daya Bay mirrored environmental conditions at each site.There were clear seasonal changes in subrogation species characteristics,which also reflected large seasonal changes in envi-ronmental conditions in Daya Bay,especially in spring,summer and autumn.Changes between autumn and winter were relatively small.The shift in dominant species composition within the macrobenthos in different years indi-cates long-term changes in environmental conditions in Daya Bay over the past 20 years.The increased dominance of polychaete worms over time suggests increased eutrophication in Daya Bay.Moreover,macrobenthic species richness was higher in recent years,and was associated with continued community structure simplification.The number of species in the 2008 samples(279 spp.) was lower than those in 1987(473 spp.).In 1987,the mean number of macrobenthic fauna in Daya Bay was 50.6 spp./station,with a maximum of 100 spp./station across sample stations.In 2008,the mean number of macrobenthic fauna was 15.0 spp./station with a maximum of 38 spp./station.