The Compositions And Implications Of Organic Matter In The Glacier Meltwater And Adjacent Coastal Seawater In The Polar Regions As Revealed By Amino Acids

It has been widely accepted that global warming is a fact.Under the sensitive response of climate warming,glaciers at high latitudes are melting and retreating more rapidly relative to before.Numerous of terrigenous material are exported into the adjacent sea,which drives biogeochemical cycle of coastal ecosystems.As the base of ecosystem material and energy flow,organic matter is essential to ecosystem,and it also plays a significant role in climate change.As important carriers of both carbon and nitrogen,amino acids(AA)are one of the few key compounds which can be identified at molecular level.In addition,it also reveals the information of early diagenetic stage of organic matter in different habitats as an effective biomarker.Based on analysis of amino acid enantiomers via high performance liquid chromatography(HPLC),this study explored the composition of organic matter in glacier meltwaters and adjacent fjord seawaters of Svalbard,Arctic(namely Ny-?lesund and Barentsburg)and in addition in Fildes Peninsula,Antarctic from the perspective of AA,which indicates the source and degradation status of organic matter.Combining with data of glacier meltwater discharge in the literature,the flux and efficiency of dissolved organic carbon(DOC),total dissolved nitrogen(TDN)and other a few key chemicals concerned that transported from glacier meltwater to ocean were estimated.With respect to the arctic samples,samples were collected in Ny-?lesund and Barentsburg in field work that carried out in Aug-Sep,2017 and Jul-Aug,2018respectively.Our results showed that concentration and compositions of organic matter in Svalbard glacier meltwater had clear spatial and temporal differences.The DOC concentration of Bayelva River in Ny-?lesund was 52±33?M,while DOC concentration of Grondalen in Barentsburg was merely 17±7?M.As for particulate organic matters,total suspended matter(TSM)and particulate organic carbon(POC)concentration were higher during melting flood season(from August to October),and they were lower at the beginning of melting season(June).Similar spatial features of organic matter components were found in Ny-?lesund and Barentsburg.As for dissolved organic matter(DOM),both Ny-?lesund and Barentsburg showed that organic matter in the glacier meltwater was less graded than in the fjord seawaters.This DOM composition pattern is consistent with literature,which suggests that glaciers are labile organic matter sources.As for adjacent fjord,the higher degradation degree of DOM reflected stronger microbial modification effect,which was similar to feature of DOM in the open sea.With respect to particulate organic matter(POM),both Ny-?lesund and Barentsburg showed opposite composition pattern of POM relative to DOM:higher degradation status was found in samples from glacier meltwaters.In the glacier meltwater,there were significant positively relations between D-AAs of POM and TSM,which suggested significant soil contribution to POM in the basin.In the fjord,however,higher DI and AA C Yield of POM indicated stronger contribution of situ production to POM.With respect to the organic matter degradability incubation experiments,we found the DOC concentration of soil leachate in Ny-?lesund and Barentsburg were very different from each other,namely 550?M and 49?M,respectively.In the ten-days photo-degradation incubation,DOC in the soil leachate in Ny-?lesund dropped to 485?M,while no significant variation can be found in corresponding soil leachate incubations in Barentsburg.In addition,the Bayelva River DOM showed very high photo-degradability(over 78%was lost),whereas its biodegradability was at trace level.As a comparison,samples were also collected in Fildes Peninsula in Antarctic in field work that carried out in Jan-Feb,2017.The results revealed higher DOC concentration in Fildes Peninsula glacier meltwater than that in Ny-?lesund and Barentsburg.For DOM compositions,a similar glacier-meltwater-to-coastal-sea pattern was found,similar to that in Bayelva River and Grondalen.As for POM,however,POM degradation proxies showed similar degradation status between glacial meltwater and fjord.suggested that degradation status of POM in glacier meltwater and fjord had no clear difference.Therefore,we identified significant differences in the spatial variability of POM degradation status between Antarctic and Arctic.Provided by Norwegian Water Resources and Energy Directorate,this work I have access to the daily automatic monitoring data of Bayelva River(at NVE station).Therefore,this work further estimated the glacier meltwater materials flux.The annual flux of freshwater and TSM of Bayelva River in 2017 was 33×10~6 m~3 and 9677 t,respectively.After using field POC sample data to calibrate the routine POC result,this work estimated the annual POC flux of Bayelva River in 2017 was 33 t.As for DOM,this work utilized 16 glacier meltwater rivers that located in Ny-?lesund and Barentsburg in Svalbard to get a better mean DOM concentration for entire Svalbard.By doing this,this work estimated the DOC,TDN and dissolved organic nitrogen(DON)annual fluxes of entire Svalbard as 7271 t,3627 t and 1697 t,respectively.Furthermore,based on the field investigations to Fildes Peninsula in Antarctic,this work estimated the DOC,TDN and DON annual fluxes of entire King George Island ice cap,which were 734 t,100 t and 4.9 t,respectively.Compared with literature,both of Svalbard glaciers and King George ice cap showed very high(even the highest)area-weighted fluxes of DOC and TDN among all other pan-polar glacier meltwaters and/or rivers(such as Siberia,Alaska and Greenland ice sheet).Although the two regions had similar TDN area-weighted fluxes,the DON proportion in TDN were entirely different:DON transported in Svalbard glaciers took up 50%of TDN,while DON transported in King George ice cap only accounted for 5%of TDN.