Study On The Ecology Of Macrobenthos In North Yellow Sea In Summer And Winter

Extensive investigations on macrobenthic communities of the North Yellow Sea carried out in summer 2006 and the next winter. The environmental factors, sediment characteristics and macrobenthos were colleted at 74 stations in summer and 78 ones in winter. Macrobenthic species composition, abundance, biomass and biodiversity were studied, as well as the relationship between macrobenthos and the environmental factors. Multivariate analysis methods were used to analyze the macrobenthic community structure and the ABC curves(abundance biomass comparison) was used to detect pollution-induced disturbance in marine benthic communities. The results were also compared with previous study to understand the change in macrobenthic community in the North Yellow Sea, and they can be used as the updated baseline for further study.A total of 359 macrobenthic taxa were recorded in this survey belonging to Coelenterata, Platyhelminthes, Nemertinea, Annelida, Echiura, Sipuncula, Mollusca, Arthropoda, Brachiopoda, Bryozoa, Echinodermata, Urochordata, Chordates, respectively. Thyasira tokunagai, Eudorella pacifica and Ampharete acutifrons were the dominant species in summer, while Thyasira tokunagai, Eudorella pacifica and Mediomastus sp. in winter.In summer, the total mean abundance, biomass were 1704 ind./m~2 and 50.63 g.wwt/m~2 respectively. The higher abundance was recorded along Shandong coastline and near Dalian Bay and ChangShan Island areas, while the abundance was lower in the central and eastern areas. Compared with abundance, biomass distribtion was even, whle it was a little lower in eastern areas.In winter, the total mean abundance, biomass were 1959 ind./m~2 and 37.77 g.wwt/m~2 respectively. The higher abundance was recorded along Shandong coastline, Bohai Strait and central part of the study area, while the abundance was lower in areas near the Korean Peninsula. The biomass was recorded higher in western areas than in eastern areas.Using a clusterisation dendrogram, three benthic assemblage types were distinguished. Type I, II, and III were titled as"Sternaspis scutata--- Sigambra Bassi---Glycinde gurjanovae assemblage","T. tokunagai---E. pacifica---Mediomastus sp.--- O.sarsii assemblage"and"Ampelisca brevicornis--- Spiophanes bombyx--Aricidea sp. assemblage"respectively. Type I occupied the shallower areas with clayey silt sediment texture and II occupied the deeper and central part of North Yellow Sea with the similar sediment texture to Type I. Type III occupied the areas near the Korean Peninsula with the sandy sediment texture.Biodiversity was high in most parts of the study area. The highest diversity was observed in Type I assemblage, while III had the lowest one. Significant relationship between biodiversity and depth and silt% was observed in the study.The ABC plots showed unpolluted conditions in most part of the North Yellow Sea except northern area which was directly influnced by freashwater from the mainland rivers in summer. Compared with communities fifty years ago, great changes of macrobenthic assemblages were observed while little within the recent ten years.