The Distribution Pattern And Spatio-temporal Variation Of Macrobenthos In The Bohai Sea And The North Yellow Sea

In order to clarify the characteristics of epifauna communities in the Bohai Sea and the North Yellow Sea,to explore their temporal and spatial changes,Six surveys were conducted at 58 sampling sites by an Agassiz net trawl trawl i in December 2014,June2015,December 2016,June 2017,December 2017,and June 2019,respectively.We analyzed the raw data based by different ways.The Index of Relative Importance(IRI)was adopted to calculate the dominant species of macrobenthos,and the Shannon-Wiener diversity index(H’),Margalef index(D)and Pielou index(J’)were used to get the biodiversity indices;The community analysis was carried out by using PRIMER 6.0multivariate statistical analysis software,including the CLUSTER hierarchical clustering method and non-metric multidimensional scaling(n MDS)ranking method.Main results were achieved as following:(1)Species composition and domiant speciesA total of 256 species of macrobenthos were identified during 6 surveys,including93 molluscan species,49 crustacean species,48 Polychaeta species,39 Fish species,16Echinoderms species,and 11 species of other group.The species composition and species number in main group taxa werewas different between summer and winter.Summer:209species,including 80 molluscan species,44 crustacean species,31 Fish species,29Polychaeta species,15 Echinoderms,and 10 species of other group;Whereas,winter:167 species,including 55molluscan species,37 crustacean species,,23 fish species,34Polychaeta species,12 Echinoderms species,and 6 species of other group.(2)Dominat speciesThe dominant species were also obviously different between summer and winter.Seven dominant species were identified in summer,namely Ophiura sarsii,Luidia quinaria,Temnopleurus hardwickii,and Crangon hakodatei,Alpheus japonicus,Chaeturichthys stigmatias and Neomysis awatschensis;Three dominant species were identified in winter,namely,Ophiura sarsii,Luidia quinaria,and Alpheus japonicus.(3)Biomass and abundanceThe total average abundance of the surveyed sea area during the summer voyage is629.02×10~3 ind./km~2,and the total average biomass is 424.25 kg/km~2.The total average abundance of winter voyages is 3939.50×10~3 ind./km~2,and the total average biomass is789.84 kg/km~2.In general,the abundance and biomass are higher in the central Bohai Sea,the Bohai Strait,and the cold water masses of the North Yellow Sea,and lower in the nearshore,while the abundance and biomass in the Bohai Bay,Liaodong Bay and Laizhou Bay are lower.Among them,The effect of Ophiura sarsii on the abundance and biomass of summer and winter voyages is the most significant.The abundance of cold water masses in the North Yellow Sea is very high.(4)Biodiversity indicesThe biodiversity in 6 voyages of macrobenthos in the Bohai Sea and the North Yellow Sea show that the average values of Margalef index D,Pielou index J’and Shannon-Weiner diversity index H’were 5.66±1.99,0.97±0.02 and 3.28±0.46 in summer,and 4.85±2.34,0.96±0.05 and 2.98±0.70 in winter,respectively..The 3 biodiversity indices of the summer voyage were higher than those of the winter voyage.Among them,the diversity index H′is higher in the far coast of the Bohai Strait and the central waters of the Bohai Sea,and lower in the North Yellow Sea and the coastal waters of Liaodong Bay,Bohai Bay and Laizhou Bay.(5)Community suffered from disturbanceThe analysis of the abundance/biomass curve shows that the epifauna communities in the Bohai Sea and the North Yellow Sea have been suffered from disturbance to a moderate or above level.Generally,the sampling sites far offshore where less disturbance were suffered,the sampling sites closer offshore where more disturbance were suffered.The main results were i)The species number,abundance,biomass and 3 biodiversity indices of macrobenthos in the Bohai Sea and the North Yellow Sea presented with an obvisous spatio-temporal difference;ii)Comparing with preverious reports,the community structure has underwent obviously changes significantly,and the epifauna resources in the Bohai Sea and the North Yellow Sea have declined overall by showing a miniaturization trend in body size and lower in economic value of some key species.