Secondary Production of Macrobenthos from Intertidal in the Changjiang Estuary and Its Impact Factors

Abstract

Macrobenthos samples were collected from three sections in the intertidal zone of the Changjiang Estuary in August 2010,November 2010 and May 2011,and the parameters of the density,biomass,secondary productivity,and P/B value of the macrobenthos were measured based on the equation by Brey(1990).The foundings indicated that the total mean density of the macrobenthos was 637.83 ind m-2,total mean biomass in ash free dry mass(AFDW) was 6.71 g m-2,total mean annual secondary productivity was 6.91 g m-2 a-1,and total mean annual P/B value was 1.01 a-1,respectively.Three sections ordered by the total mean density,biomass,secondary productivity,and P/B value was Dongwang sand Buyu port Tuanjie sand.The secondary productivity was mainly influenced by Crustacea with six critical species,including Corbicula fluminea,Potamocorbula amurensis,Sinonovacula constricta,Stenothyra glabra,Bullacta exarata and Cerithidea sinensis,and the six species contributed 65.24% of the total.Based on the data of total mean annual P/B value(1.01 a-1),It was speculated that the average change of macrobenthos was year-generation,and community structure was instability and obviously influenced by the environment.The analyses of secondary productivity combination of variables indicated that the secondary productivity was not only impacted by the biomass and density but also by the total nitrogen and total phosphorus of water.The results of Principal Components Analysis(PCA) on the environmental variables showed that the environment in Tuanjie Sand was the most stable,Buyu Port was less stable,and Dongwang Sand was the most violent one.The relationship between environmental variables and the secondary productivity of community was analyzed using Canonical Correspondence Analysis(CCA),and Sa,TP,TOC and DO were found to be the key factors to the secondary productivity in Dongwang Sand macrobenthos communities;TN,TOC,Chla and DO in Buyu port.Furthermore,the habitat of Tuanjie Sand was the most stable,and all the environmental variables of this region rarely changed,so it was speculated that the physical factors were the key factors of the secondary productivity.