Exploration Of Relationship Between Diatom Distribution Of Surface Sediment And Environmental Factors In The East Siberian Sea

Climate change is a major challenge to society,especially in Arctic regions,where acceleration of climatic and environmental changes is particularly marked by the drastic reduction of summer sea-ice cover and melting of continental ice caps.Sea ice is a critical component in the global climate system that contributes to changes in the Earth’s albedo and deep water formation,a driving mechanism for global thermohaline circulation.The East Siberian Sea is one of the Arctic Ocean marginal sea where have a profound impact on global climate change through various positive and negative feedback mechanisms.Due to lack of sediment cores and poor temporal resolution,the East Siberian Sea sea ice reconstructions are sparse.This underlines the importance of quantitative reconstructions of sea ice in the East Siberian Sea and its adjacent seas.In this study,diatoms from surface sediment samples in the East Siberian Sea and its adjacent seas were analyzed to reveal the distribution pattern of the surface sediment diatoms and their relationship with the ocean environment.A total of 98 taxa were identified from 39 surface sediment samples in the East Siberian Sea and its adjacent seas.The main species include Bacterosira bathyomphala、Detonula confervacea resting spores、Entomoneis spp、Fragilariopsis cylindrus、Fragilariopsis oceanica、Navicula distans、Nitzschia frigida、Nitzschia laevissima、Nitzschia promare、Paralia sulcata、Pauliella taeniata、Pleurosigma spp、Rhizosolenia hebetata、Thalassionema nitzschioides、Thalassiosira antarctica var.borealis resting spores、Thalassiosira cf.antarctica var.borealis resting spores、Thalassiosira gravida、Thalassiosira hyalina、Thalassiosira hyperborea、Thalassiosira nordenskioeldii、Thalassiosira spp。The results of the cluster analysis and the PCA of diatoms from 39 surface sediments samples and the environmental variables(sea surface temperatures,sea surface salinity and sea ice concentration)shows that Autumn sea surface temperatures、Summer sea surface temperatures、Autumn sea ice concentration and Summer sea ice concentration are the main environmental factors affecting diatom distribution in the East Siberian Sea and its adjacent seas.Four diatom assemblages are distinguished based on scores of species and samples.Group I is distributed in the east coastal waters of the Long Strait and the East Siberian Sea(i.e.the West and south areas of Wrangel Island).The main taxa are sea ice diatom species F.cylindrus、F.oceanica、T.hyperborea、N.promare、N.distans、N.laevissima and arctic diatom species T.antarctica var.borealis resting spores、T.nordenskioeldii、B.bathyomphala、D.confervacea resting spores、T.gravida.The abundance of sea ice diatoms is about 65%,the and the abundance of warm water diatoms T.nitzschioides is less than 2%.The corresponding marine environment is between Group II and III.Group II is distributed in the west side of Chukchi Sea and on the east side of Wrangel Island.The main diatoms are arctic diatom T.antarctica var.borealis resting spores、B.bathyomphala、T.cf.antarctica var.borealis resting spores、T.nordenskioeldii;and warm water diatoms T.nitzschioides、P.sulcata.The abundance of arctic diatoms is about 37%,and the abundance of warm water diatoms is about 15%,which is suitable for the high temperatures,high salinities and low sea ice concentration.Group III is distributed in the west、central and northern part of the East Siberian.The main diatoms are sea ice diatoms F.cylindrus、F.oceanica、T.hyperborea、N.distans、N.promare、E.spp、P.taeniata.The abundance of sea ice diatoms is more than 70%which is suitable for the environment with low temperatures,low salinities and high sea ice concentration.Group IV is distributed in the basin to the north of the East Siberian Sea slope.Due to the poor marine environment(low sea surface temperatures and high sea ice concentration),diatoms is extremely rare or even absent.It reflects the differences of diatom assemblages in different marine environments.The correlations between diatom species,sample sites and environmental variables concur with known diatom ecology and regional oceanographic characters.This confirms that the diatom samples from surface sediments used in the analysis are recent.