Characteristics Of Macrobenthic Community Structure In The Yellow Sea And East China Sea

Macrobenthos is a key component in marine ecosystems, playing a vital role indetritus decomposition, matter cycling and energy flow to higher trophic levels. Thisfaunal component has been frequently used in environmental quality assessment ofmarine systems. The present study evaluates whether benthic communitiescharacteristics, the trophic structure of macrobenthos, environmental variables andtheir relationships change at research areas parts of the the Yellow Sea and East ChinaSea, an ecosystem with pronounced temporal-spatial variation of macrobenthiccommunities, depth, water quality and sediment properties. The main goal of thepresent study was to clarify the complex link between abiotic and biotic interactionsand knowledge about dynamics of macrobenthic assemblages succession, multivariateanalysis approaches were used both for taxon and for the trophic groups‘composition,using abundance data. In order to understand the mechanisms of dynamics of coastalecosystems and environmental conditions through targeted studies on changemechanism on macrobenthic communities and provide scientific data for the furthermarine ecological research of the Yellow Sea and East China Sea.The present study, based on six cruises surveys (Oct2000, Mar2001, June2003,Jan2004, Apr and Aug2011), focused on the spatial and temporal distribution of themacrobenthic community from the Yellow Sea to the East China Sea, in order todetermine the structure and trophics‘of macrobenthos in the research areas and itsrelationships with environmental conditions, to evaluate the suitability ofmacrobenthos taxonomic diversity indices to discriminate among different levels ofhuman impact and eutrophication, to estimate the feeding diversity and ecosystemhealth of the research area using the Pielou’s evenness index (J’FD), Infaunal TrophicIndex (ITI), and a Marine Biotic Index (AMBI), and to reveal the species ability toutilize the environmental resource. by niche analysis of dominant species ofmacrobenthic community in the southern Yellow Sea. A total of429macrobenthic species were collected from the six cruises. Themain taxonomic groups identified were polychaeta (169taxa), Crustacea (112taxa),Mollusca (89), echinordemata (44) and other groups (15). Comparing with theprevious findings in same areas, distinctly difference of species number of taxagroups were observed. The results showed the number of polychaeta species hasincreased, while species number of Crustacea and Mollusca has trended down in past50years. Thirteen species identified occurred at frequencies higher than20%:Nephtys oligobranchia, Notomastus latericeus, Ophelina acuminate, Goniadamaculate, Nin e palmate, Sternaspis scutata, Glycera chirori, Onuphis geophiliformis,Lumbrineris longifolia, Nucula tenuis, Thyasira tokunagai, Callianassa japonica andOphiura sarsii vadicola. The dominance value of N. oligobranchia, N. latericeus andN. tenuis were higher than0.02.The mean values of abundance and biomass varied from123.03to237.73ind/m2and from11.2to29.12g/m2, respectively. The standing crops have certain regularityin distribution in study areas. The characteristic of high stability of distributions ofstanding crops maintained in the Yellow Sea cold water mass area. The abundance ofopportunistic polychaeta species, small individual size, were far greater in the mostadjacent waters of coast and estuary due to organic enrichment conditions by runoffand frequent and extensive disturbance events.The mean values of three indices range from:3.14to4.43, from0.67to0.87forand from1.69to2.39for richness index (D), Pielou evenness index (J’) andShannon-Wiener index (H’), respectively. The lowest mean values of D (1.69) and J’(3.16) were recorded in April2011.The investigation revealed that average taxonomic distinctness (AvTD) andvariation in taxonomic distinctness (VarTD) of March2001and April2011felloutside the95%confidence funnel limit implying taxonomic instability. Inspatial-scale, the AvTD and VarTD of the macrobenthos are in habitats which locatedat the adjacent waters of southern Yellow Sea, Yangtze River estuary and Zhejiangcoast, fell below the95%confidence limits suggest that habitats are degraded andmacrobentic communities have unitary structure. Macrobenthos abundance data were subjected to the CLUSTER routine andassociated SIMPROF procedure in the PRIMER v6multivariate statistical package toquantitatively identify different groups of sites represented community types (theYellow Sea cold water mass communities and the coastal and estuary communities) instudy areas. Four, five and eight main clusters were identified by in six cruises,respectively, which were shown to well reflect spatial differences in study areas. TheYellow Sea cold mass communities structure were relatively stability, and werecharacterized by cold species O. sarsii vadicola, N. palmate and T. tokunagai. Thecoastal and estuary community structure were relatively depauperate, containing highnumbers of opportunistic polychaeta species and abundances, and were characterizedby N. latericeus, N. oligobranchia, O. acuminate and Aricidea fragilis. Canonicalcorrespondence analysis (CCA) and BIOENV showed that depth, bottom watertemperature, sediment median grain size and total organic carbon content were thekey environmental parameters may influence the distributon of macrobenthic fauna inApril and August2011.The trophic structure of benthic communities in study area was characterizedaccording to a functional guild approach, based on sampling surveys conducted6cruises. Macrobenthos were assigned to six distinct trophic groups (herbivorous, filterfeeders, deposit feeders, deposit feeders, carnivores, filter feeders and detritus feeders)and the dominance of these groups was related to environmental variables usingmultivariate ordination techniques. Deposit feeders and carnivores were numericallydominant in the study areas, making up high50%of benthic communities. In spatialscale, the adjacent waters of Yangtze River estuary, coastal waters of southern YellowSea and Zhejiang province contained containing high abundances values of depositfeeders and carnvores, and were characterized by N. latericeus, N. oligobranchia, O.acuminate and Aricidea fragilis. Expansion of the distribution areas of dominanttrophic groups was observed along temporal scale in study areas. The redundancyanalysis (RDA) results of indicated that bottom water temperature, salinity and depthwere significant predictors of community trophic structure variance (p<0.05).The feeding diversity and ecosystem health of the study area was estimated using the Pielou’s evenness index (J’FD), and Infaunal Trophic Index (ITI), applied inconjunction with a Marine Biotic Index (AMBI). The assessment results showed mostof the stations in the study area exhibited good or high feeding diversity,corresponding to a healthy ecological state, with the exceptions of stations in adjacentwaters of the Yellow Sea and Yangtze river eatuary that showed occasionally lowfeeding diversity, ITI and AMBI values. The poor condition at these stations wasmainly related to disturbance impacts and natural accumulation of organic matter,with some feeding groups being absent or present at low relative abundances, withone or two groups dominating the community, which was particularly the case withdeposit feeders. Such temporal scale expansion the moderately or heavily disturbedareas located in adjacent waters of Yangtze estuary were observed.To determine the niche of the macroinvertebrate communities in the southernYellow Sea,20dominant species were selected. The Shannon-Wiener’s Niche Breadthindex, the Pianka Niche Overlap index, Outlying mean index (OMI) and Toleranceindex (TOL) were used to analysis the relationships of the dominant species andenvironmental factors. The Shannon-Wiener’s Niche Breadth index varied from1.24to2.15. T. tokunagai, O. geophiliformis, N. palmate, O. sarsii vadicola,Ehlersileanira hwanghaiensis and Glycinde gurjanovae had large niche breadths.Outlying mean index varied from0.23to4.95. Paralacydonia paradoxa and Glyceratenuis had higher value of Outlying mean index than that of any other species.Tolerance index ranged from0.13to3.85. Sigambra bassi, N. oligobranchia and E.hwanghaiensis were the main contributors to the Tolerance index. Niche overlapsvaried from0to0.95. L. longifolia and N. palmate had a niche overlap value closed to0.95. The significance of the random permutation test of the OMI analysisdemonstrate that niche segregation of G. chirori, G. tenuis, N. latericeus, O.acuminate and O. sarsii vadicola is effective along a given gradient (e.g., depth, waterbottom temperature, salinity, median size and total organic carbon and total nitrogencontent of sediment)(p<0.05)..In the past decade, within the adjacent waters of the Yangtze river estuary, wheredisturbance envents are common (e.g. dredging, overfishing, sewage discharges, summer hypoxia, red tide), changes in the ecological quality status can result fromdifferences in the dominance of a single taxon. The macrobenthic communitystructure was relatively depauperate, containing high numbers of opportunisticpolychaeta species and abundances. On the contrary, within the Yellow Sea cold massarea, the communities structure, from anthropogenically stressed, maintained aslightly disturbed condition, and were dominanted by cold species as before. Depth,bottom water temperature and sediment composition were the main factors structuringspatial distribution.The following four broad innovation points were addressed in this study.(1) Toascertain that the characteristics of the macrobenthic communitities in the Yellow Seaand East China Sea nearly10years, and that the patterns of those temporal-spatialdifferences matches those among the environmental characteristics that were used todistinguish those community types;(2) To use four taxonomic diversity indices fordescribing taxonomic diversity chacracteristics of macrobenthic communities in studyareas that employs readily-available species data;(3) To use the Pielou’s evennessindex (J’FD), and Infaunal Trophic Index (ITI) and apply in conjunction with aMarine Biotic Index (AMBI) for estimating the feeding diversity and ecosystemhealth of the study area;(4) To use niche analysis of dominant species ofmacrobenthic community in the southern Yellow Sea for revealing the species abilityto utilize the environmental resource. Overall, the above biological validation ofmacrobenthic community studies provided big amount of scientific data for thefurther marine ecological research of the Yellow Sea and East China Sea, namely todevelop a quantitative scheme for understanding the mechanisms of dynamics ofcoastal ecosystems and environmental characteristics.