"Biological Pump" And Its Response To Changes In Sea Ice In The Prydz Bay, East Antarctica

Polar region is an important sink of global carbon cycle.In the context of global climate change,the operating efficiency and change of biological carbon pump?BCP?in polar region impact on global carbon cycle significantly.Antarctic sea ice presents an inhomogeneous trend,and the impact on polar biological pumps needs to be evaluated.Sinking particulate samples from time-series sediment traps and other data of upper ocean were obtained in Prydz Bay of Antarctica from 2009 to 2015,to study the strength,efficiency,and control factors of BCP.Combined the data of sea ice and chlorophyll-a of remote sensing,stable isotopes of carbon and biomarkers?unsaturated C 25 highly branched isoprenoids,HBIs?were used to further investigate the response of carbon fluxes to sea ice changes in Prydz Bay.The following are the main conclusions of this work:?1?The average annual flux of organic carbon in the Prydow Bay at a depth of450m is 253mmol C m^-2 yr^-1,which is significantly higher than that outside the bay.Seasonal and inter-annual variations are obvious and are controlled by factors such as sea ice and light.Diatoms and diatom detritus are the main components.Using the Martin curve to normalize the organic carbon fluxes in different sea areas of the Southern Ocean to a depth of 100m,it was found that there was little difference in the annual fluxes of the various sea areas.?2?The export efficiency and transport efficiency of Prydz Bay in 2010/2011 were11.4%and 3.4%respectively,compared with 4.9%and 1.1%in 2014/2015 respectively.which were lower than the average of the Southern Ocea,indicating the efficiency of BCP in Prdyz Bay is relatively inefficient.High primary production and low efficiency of BCP occurred in 2014/2015.The reason may be that sea ice ablation in advance increased temperature and the advanced of phytoplankton bloom,which may promote the increase of bacterial productivity,together with the lack of effective ballasts such as ice-rafted detritus,more organic matter would stay in the upper layer for decomposition and recycling,which results in a decrease in the efficiency of BCP.?3?There is a clear response of HBIs to the ablation and freezing of sea ice,which can better reflect the changing process of sea ice.The average annual carbon flux contributed by the algae was 82.33?mol m^-2 d^-1,and the carbon flux in the summer was120?mol m^-2 d^-1,accounting for 18.6%and 23.6%of the total carbon flux,respectively.The amount of carbon deposited in the summer by ice algae accounts for 22.1%of the carbon storage in sea ice.The co-sedimentation of ice algae and ice-rafted detritus may be the main reason for its high efficiency.In the future,the diatom productivity in the Antarctic waters may increase due to the increase in temperature and availability of iron.However,there is still great uncertainty in the changes in the efficiency of BCP,making the trend of changes in Antarctic marine bio-pumps more complex.Long-term observations and studies are needed to assess the future carbon sequestration capacity of the Southern Ocean.