Quantitative Research On Ecological Information Of Recent Ostracods In The Coastal Zone Of The East China Sea

Ostracods,a benthic crustacean,not only are sensitive to environmental changes,often as a bioindicator,widely used in the study of environmental changes;but also have a well-preserved fossil record,which is an important testimony to the evolution of paleoceanology and paleogeography.The fossil assemblage of ostracods in geological research can be explained by the ecological information of extant taxon,and then reconstruct the paleoenvironment and paleoclimate in geologic time,so the study of recent ostracods is of great value to the modern water environment and the ancient environment.In this study,the coastal zone of the East China Sea was taken as the Survey Region,and the Yangtze Estuary,the East China Sea continental shelf and the Xiangshan Harbor were selected as typical waters to study the composition,abundance,dominant species,biodiversity,and community structure characteristics of recent ostracods in surface sediments,establishing the ecological information database of recent ostracods in coastal zone of the East China Sea.Based on this,the relationships between ostracods and environmental factors were explored,and a quantitative transformation function between the ostracod assemblage and the most influential environmental factors on its distribution was established by waters.The relevant studies have important reference value for predicting the evolution process of paleoenvironment and understanding the history of coastline changes in the East China Sea by using ostracods.The specific contents of this study include:1.the Yangtze Estuary and the East China Sea nearshore continental shelfThe Yangtze Estuary and its nearshore continental shelf are the open waters of the East China Sea.In this study,43 species of ostracods were found in spring?April2015?and summer?July 2016?,of which 38 species were found in summer and 37species in spring.The common dominant species in two seasons were Bicornucythere bisanensis,Pistocythereis bradyformis,Cytherelloidea yingliensis and Aurila cymba.Among them,Bicornucythere bisanensis was the first dominant species and Pistocythereis bradyformis was the second dominant species in the two seasons.In addition,Munseyella japonica,Actinocythereis triangulata,Stigmatocythere costa were the dominant species in summer and Albileberis sinensis in spring.In the summer of 2016,the distribution of ostracods in the Yangtze Estuary and the offshore continental shelf of the East China Sea were mainly affected by the currents,resulting in regional differences in species mean abundance and diversity distribution,showing that Taiwan warm current area?area??>coastal current control area?area??>estuary area?area??.Canonical Correspondence Analysis?CCA?found that water depth was the largest environmental factor affecting the distribution of ostracods in summer,followed by dissolved oxygen and p H.Based on the results of CCA,the ostracods-water depth conversion function R²_Jack=0.6609,RMSEP_Jack=0.1847 was made by using the functional mode WA-PLS?5 component?.The established transformation function has certain reliability and deducing ability.In the spring of 2015,due to seasonal variations in the area,the Shannon-Wiener diversity index?H'?and Margalef richness index?D?were lower than those in summer,but the Pielou evenness index?J'?was the same.And the diversity indices and average abundance also showed that Taiwan warm current area?area??>coastal current control area?area??>estuary area?area??.Canonical Correspondence Analysis?CCA?found that water depth,turbidity and water temperature were the main environmental factors affecting the distribution of ostracods in spring.In general,the estuaries and the inshore in two seasons were seriously polluted.2.Xiangshan HarbourXiangshan Port is a typical area of semi-enclosed bay in the coastal zone of the East China Sea.In this study,26 species of ostracods were identified in the summer of2017,of which 7 were dominant species namely Pistocythereis bradyformis,Aurila cymba,Sinocytheridea impressa,Bicornucythere bisanensis,Keijella hodgii,Neomonoceratina dongtaiensis and Alocopocythere kendenensis.Redundancy analysis?RDA?analysis showed that the Mud content was the key factor affecting the distribution of ostracods,followed by water temperature and dissolved oxygen,and the Ostracod-mud content transfer function,R²_Jack=0.6122,RMSEP_Jack=0.098 was made by using function WATOL?Classical?model,the established function has a certain degree of credibility and derivation.In addition,the Shannon-Wiener diversity index?H'?,Pielou evenness index?J'?,and the Margalef richness index?D?,all of them showed that the whole Xiangshan Harbour was disturbed,in a polluted state.The three major ports?Iron Port,Huangdun Port and Xilu Port?,the power plant area and the artificial reef area were seriously polluted.