Research On Marine Picoplannkton Spatial Distribution And Environmental Effection At Pacific Section Of Arctic During Summer

At recent decades,Arctic changed quickly as global warming.An Arctic Rapid Change named "Unaami" was happened at Arctic Ocean,including sea ice coverage decreasing,sea ice thickness reduction,sea surface temperature increasing,salinity reduction,intermediate water warming,landing glacier melting,freshwater inflow increasing and surface water being more and more oligotrophic.All of these will play and are playing important role at ecosystem of Arctic Ocean.As one of the most important component of Arctic marine ecosystem,picoplankton is sensitive to environmental variation and could be well indicator of Arctic Ocean changing.Meanwhile,picoplankton also was the main primary producer of Arctic Ocean and played important role in Arctic energy and element cycling and carbon fixing.The 3rd and 4th Chinese National Arctic Research Expedition at 2008 and 2010 provide us an opportunity to the wide range and large-scale investigation toward the environmental situation and picoplankton distribution at Arctic Ocean.It will help us to know the picoplankton community structure and biodiversity of Arctic Ocean.Besides,relationship among distribution characteristic,water temperature,salinity,nutrients and water masses was also analyzed to know the marine ecosystem constitution and picoplankton distribution pattern.Annual variation was also investigated.These will help our country to the development and exploitation of Arctic resources.Results of investigation toward environmental situation at Arctic Ocean and subarctic of Pacific concluded as:1.A warm surface layer with water temperature higher than 5? was appeared at Bering Sea,and could reach a latitude of 65° N,70° N,69° N and 73° N at Chukchi Shelf on August,September 2008,August and September 2010,separately.2.Alaskan Coastal Water with high temperature,low salinity and low nutrients concentration constitute the upper 20m layer of Bering Shelf,and when below 20m,they were Bering Shelf Water and Anadyr Water with higher salinity.Anadyr Water contributed fewer percentage of water mass at Bering Shelf on 2010.Besides the Pacific inflow,the north Chukchi Sea also infected by the Arctic Ocean Surface Mixed Water and formed the low salinity and oligotrophic surface water.The upper 100m layer of Canada Basin was mainly constitute by low salinity Arctic Mixed Surface Water and Pacific Water including Alaska Coastal Water and Bering Shelf Water.As latitude increased,Pacific Water transited to the surface with the increasing influence of Beaufort Gyre,Boundary Upwelling of Canada Basin and Pacific/Atlantic Front,and when getting across the Alpha Ridge,Pacific Water reached the surface.3.Compared with 2008,most survey area got increased average water temperature,especially the shallow shelf area.Average water temperature increased from 2.52 to 3.10,2.38 to 3.01,0.79 to 1.44 and 1.94 to 2.25 at Bering Shelf,Bering Strait,Chukchi Sea(outward)and Chukchi Sea(backward),separately.However,average water temperature remained stable,and some survey area even appeared decreased water temperature.The increasing average water temperature was mainly caused by the increasing temperature of Pacific inflow,also means the increasing influenced of Pacific Water to Arctic Ocean.4.Average nutrient concentration decreased at the survey area from 2008 to 2010.Most importantly,average nutrient concentration of Canada Basin was higher than at Chukchi Plateau,means the decreasing and even missing transportation probability of Chukchi Shelf to Canada Basin,and upper layer of Arctic Ocean would be more and more oligotrophic.Results of picoplankton distribution investigation at Arctic Ocean and subarctic of Pacific concluded as:1.Picophytoplankton was the most important component of Arctic and subarctic of Pacific marine ecosystem,it constitute an average of 55%,40%and 67%of total Chl a concentration at Bering Basin,Chukchi Sea and Canada Basin,separately.2.Synechococcus distributed mainly at Bering Basin,with an abundance ranged from 0.01 to 41.27 cells/?l(average of 4.20 cells/?l)and from 0.06 to 22.89 cells/?l(average of 4.80cells/?l)at 2008 and 2010.At Bering Sea,compared with 2008,Synechococcus with abundance larger than 1 cells/?l distributed 0.43° north than at 2010.And when at Chukchi Sea(backward)2010,it was also 0.5° north than at 2008.Besides,new distribution area at section MS at Canada Basin and section M at Mendeleev Ridge were found at 2010,and these confirmed the increasing influence of Pacific Water to Arctic Ocean.3.Average Picoeukaryotes abundance at Bering Basin,Bering Shelf,Chukchi Sea(outward),Chukchi Plateau,Chukchi Slope,Canada Basin(outward),Canada Basin(backward),Mendeleev Ridge and Chukchi Sea(backward)were 7.18,3.69,2.27,2.56,2.01,2.09,1.92,4.08,2.48,2.25 cells/?1 on 2008 and 8.81,3.81,2.87,2.72,2.29,3.02,2.29,1.79,2.43,3.04 cells/?l on 2010.All reveals the higher abundance at Basin area than Shelf area and higher at Arctic than at subarctic.Average picoeukaryotes abundance of each survey area increased from 2008 to 2010,which was correlated with water temperature increasing and nutrient concentration reduction.It was a responds of picoeukaryotes abundance increasing to Arctic Surface warmer and more oligotrophic,it was also a responds of picoplankton to Arctic Rapid Change.4.Average Heterotrophic Bacteria abundance at Bering Basin,Bering Shelf,Chukchi Sea(outward),Chukchi Plateau,Chukchi Slope,Canada Basin(outward),Canada Basin(backward),Mendeleev Ridge and Chukchi Sea(backward)were4.80,,6.10,5.31,5.46,1.80,2.19,1.55,3.26,2.88,7.83×105cells/ml at 2008 and 1.63,1.79,2.56,1.45,0.47,0.5,0.69,0.39,1.46× 105cells/ml.Average heterotrophic bacteria abundance decreased from 2008 to 2010,it might correlate with the nutrient concentration reduction.5.Picoplankton distributed mainly at 10m-30m of Bering Basin and upper Alaska Coastal Water of Bering Shelf.The peak of picoplankton abundance at Chukchi Sea and Canada Basin were also usually correlated with warmer,lower salinity and lower nutrient concentration Alaska Coastal Water.6.Picoplankton abundance higher than 1 cells/?l was usually appeared at Alaska Coastal Water or Arctic Mixed Surface Water,with salinity lower than 31.8 PSU.And the picoplankton abundance peak(higher than 5cells/?L)was also appeared at Alaska Coastal Water with salinity about 30.5 PSU.When getting across the Alpha Ridge and reaching the Makarov Basin,Pacific Water and Atlantic Water meet here,picoplankton abundance peak transited to the surface in combine with Pacific Water,especially Alaska Coastal Water transition to the surface.We may indicate the Pacific/Atlantic Front via the transition of picoplankton abundance peak.7.There were significant positive correlation of picophytoplankton abundance with water temperature and significant negative correlation with salinity and nutrients.Significant correlation between picophytoplanton abudance and water masse was also found.We cannot identify water mass only via picophytoplanton abundance,however,combine with salinity,we successfully separate water masses.Picoeukaryotes could also be important indicator of Arctic water masses.