Ecological Studies On Macrobenthos In The Xiangshan Bay

For years, macrobenthos research has been paid much attraction by scholars. A seasonal research of macrobenthos was carried out in Xiangshan Bay from July, 2006 to August, 2008. The sampling stations covered most of the sea area in Xiangshan Bay. The macrobenthic community was anglicized by the species richness index (d), species evenness index (J), species diversity index (D) (H '). The ABC Curve method and PRIMER5.0 were adopted to analyze the Bray-Curtis similarity matrix and MDS analysis of macrobenthos in Xiangshan bay. The abundance, biomass, secondary productivity, and P /B value of the macrobenthos were studied by using Brey's empirical formula, and the composition of the dominant species in Xiangshan Bay of the macrobenthic community was studied by using calculation of species dominance. The huge covered research area and the method of functional group based on diet habits were also used to study the macrobenthic community composition and diversity.The main conclusions in this research are the following:The research showed that 123 species were found in the area, including 48 species of mollusk, 33 species of crustacean, 12 species of fish and 12 species of filose, 8 species of echinoderms and some coelenterate, nematodessp. The dominant species in fauna is more concentrated, and the dominance index was higher.The macrobenthos in Xiangshan Bay is unevenly distributed. Compare to the result based on the research at main channel ocean, the biomass and inhabited density in the harbor area were evidently higher. Meanwhile, the biomass and inhabited diversity in area near power plant was much lower than normal area in the bay. The study also shows that for the inhabited density and biomass, the season change has less influence to the power station area than the normal area. Because the warm water from the power plant reduce the seasonal difference of water temperature.The secondary productivity of the macrobenthos was averagely 16.70g/(m2.a),and the mean P /B value was 0.60. The data of species richness index (d), evenness index (J), Simpson's diversity index (D), and Shannon - Wiener diversity index (H') were analyzed for two-factor analysis of variance by the factors of stations and anniversary. The results shows that the differences of four kinds of indices between the different stations were dramatically significant, but the differences of four kinds of indices between the different years were not so clearly showed. From the view of species diversity alteration, we found out that the diversity of macrobenthos at Xiangshan bay has reduced, it means that macrobenthos in Xiangshan Bay have been unable to maintain the original state, its ability to self- adjustment has reduced and the ecosystem of Xiangshan Bay can hardly maintain its stability.The result of CLUSTER and MDS shows that the macrobenthic community of the Xiangshan Bay constitutes three groups. The results of ABC Curve method indicated that the macrobenthic community is affected by pollution and other human activities, it had been gradually dominated by one or several types of smaller species.The huge coverage of research area and the method of functional group based on diet habits are used to study the macrobenthic community composition and diversity. According to their food preferences, the zoobenthos were classified into 5 ecological functional groups: they are planktophagous group(Pl) , phytophagous group (Ph) , camivorous group (C) , omnivorous group (O) and detritivorous group (D) . The species numbers of each functional groups constituted the percentages of total benthos in proper order is C>Pl>O>D>Ph; the inhabited density of each functional groups constituted the percentages of total in proper order is Pl>C>D>Ph>O, and the biomass of each functional groups constituted the percentages of total in proper order is Pl>D> C>O>Ph. The average annual data of species numbers, inhabited density and biomass were analyzed for two-factor analysis of variance by the factors of stations and anniversary. The results shows that the differences between the different stations were highly significant for three kinds of data and the differences between the different years were not so obvious. It is verified that the structure of macrobenthic functional groups is synthetical reflection of habitat gradient and fluctuation of natural environmental factors.