Biodiversity Analysis Of Bacterioplankton In Amundsen Sea,Antarctica

Bacterioplankton plays a very important role in the marine ecosystem in polar regions and plays an important role in stabilizing the marine ecosystem and responding to global climate change.In recent years,following the increasing of the local temperature and the flux of the ice-melted fresh water,ecosystems in the Southern Ocean has been changing and received more attention.In the southern ocean,bacterioplankton such as community composition,spatial distribution,seasonal variation and the regulation mechanism of environment has been studied by many researchers,however,there is still a large gap compared with other area on the earth.China’s research on bacterioplankton in the Southern Ocean is extremely limited.The Amundsen Sea,one of the most significant warming regions in the West Antarctica and the most affected sea area by global climate change,is the least sampled and least studied region in the Antarctic.In this study,the data collected during 36 th Chinese National Antarctic Research Expedition(CHINARE-36)is used.The environment parameters and the structure of the bacterioplankton community, together with their relationship,are studied.The differences of bacterial community structures among Amundsen polynya,waters north of the polynya,and waters wester of the Amundsen Sea,are compared.And the future research contents is prospected.The main results of this study are as follows:Affected by global climate,the surface water temperature of the Amundsen Sea is highest compared with the the middle and deep waters.In the sub-surface,there is a winter residual water,in which the lowest temperature occurs.Horizontally,the maximum of the temperature is observed in the surface waters in the Amundsen polynya,followed by the waters north of the Amundsen polynya.The temperature in the waters west of the Amundsen Sea was lowest.Affected by fresh water input from the ice shelf and melting sea ice in summer,the surface salinity of the Amundsen Sea is relatively lower,however,the salinities increase with the increase of depth,but in general,the variation was small along the vertical profiles.The temperature of surface water in the Amundsen Sea decreases from west to east and the salinity increases.The concentrations of dissolved oxygen(DO)decreases in the sub-surface and then increase of depth.The nutrient concentrations are low.The concentrations of nitrate,phosphate and silicate all increase with the depths.However,the ammonium has a peak in teh sub-surface in the polynya.The chlorophyll a concentrations are higher in polynya,and the contribution of size-fractionated chlorophyll a concentrations to total chlorophyll concentration are different among the three Amundsen Sea.Compared with the three areas,the relative abundance and biodiversity of Proteobacteria are 38.15%,49.58% and 43.53% in polynya,north of polynya and west of Amundsen Sea,respectively.The relative abundance of actinomycetes is the secend highest,23.36% in polynya,21.99% in northern polynya and 12.85% in western Amundsen Sea,respectively.The proportion of OTU of Bacteroidetes was second only folowing that of Proteobacteria.In addition,Firmicutes replaced proteobacteria act as the dominant group in some sites.The number of bacterioplankton species at each classification level is the largest in the northern part of the polynya,and the smallest in the polynya.The diversity and species richness of bacterioplankton in polynya and northern waters increase with depth.The diversity and species richness of plankton in the western Amundsen Sea are higher than those in waters far from the Antarctic continent.The biodiversity of bacterioplankton in polynya was higher than other waters.The biodiversity of bacterioplankton in the area near the polynya was higher than that in the area far away from the polynya.The biodiversity of bacterioplankton in polynya is related to salinity,dissolved oxygen,nitrite,silicate and ammonium.The bacterioplankton biodiversity in waters north of the polynya is correlated with temperature,salinity,dissolved oxygen,nitrite,nitrate,phosphate and ammonium except for silicate.The bacterioplankton biodiversity in the west of Amundsen Sea is only correlated with silicates in nutrients.In general,the bacterioplankton community in the Amendsen polynya is differnet from the arounding waters,influenced by factors such as the melting water.