Study On The Spatiotemporal Variation Of Dimethyl Sulfide In The Bering Sea

Bio-sulfide is a kind of sulfur-containing substances that are produced,utilized,or converted by organisms,their role is critical in the global cycle of sulfur.As the most important volatile sulphide in the ocean,dimethylsulfide(DMS)plays a significant effect in global environmental issues such as global climate change and acid rain.As the precursor of DMS and its important oxidation products,Dimethylsulfoniopropionate(DMSP)and Dimethyl sulfoxide(DMSO)can affect greatly the content and distribution of DMS.The water mass,an important function unit of the ocean water,can influence the biogeochemical process of the Bio-sulfide directly.Therefore,the study of spatiotemporal distribution of sulfide and its impact factors which based on the characteristics of the water mass would contribute to understanding of the mechanism of the change of the Bio-sulfide distribution,so as to provide a new study idea on the impact of sulfur on marine environment.The polar and sub-polar sea areas can amplify the micro-effects caused by global climate change,thus play an effective role in indicating of climate change.Based on the field data in the Bering Sea during the 5th to 7th Chinese arctic expedition,this paper analyzes the spatiotemporal variations of bio-sulfide(DMS,DMSP and DMSO)and their influencing factors in the Bering Sea.The main results are as follows:1.The Bering Sea Basin consists of three water masses,i.e.Bering Sea Basin Upper Water,Bering Sea Basin Intermediate Water,and Bering Sea Basin Deep Water.The Bering Sea Basin Upper Water has the characteristics of high temperature,low salinity,high dissolved oxygen,high chlorophyll and low nutrients.The Bering Sea Basin Intermediate Water is characterized by low temperature,and the concentrations of the other elements are between those of the Upper and the Deep Water.The Bering Sea Basin Deep Water has the characteristics of low temperature,high salinity,low dissolved oxygen,high nutrients and low chlorophyll,especially the silicate concentration is much higher than those of the sea area with the same latitude.There are four water masses in the central of Bering Sea shelf,namely,Bering Slope Current Water(BSCW),Mixed Water(MW),Bering Shelf Surface Water(BSW-S)and Bering Shelf Cold Water(BSW-C),in which the Bering Shelf Surface Water has high temperature,low salinity,low nutrients,and low chlorophyll;Bering Slope Current Water with high nutrients and low chlorophyll characteristics;Bering Shelf Cold Water with low temperature,high dissolved oxygen,and high chlorophyll characteristics;Mixed Waters' characteristics between the Bering Slope Current Water and Bering Shelf Cold Water.The northern Bering Sea shelf is divided into three water masses,Anadyr Water,Alaska Coastal Water and Bering Shelf Water.Anadyr water has characteristics of low temperature,high salinity,high nutrients,low chlorophyll,low dissolved oxygen;Alaska Coastal Water is high temperature,low salinity,and low nutrients;Bering Shelf Water is characterized by high dissolved oxygen and chlorophyll.In addition,the Bering Sea area in 2012 for the cold,2014 and 2016 for the warm year,so the temperature of water mass is the lowest in 2012.2.2012 is the cold year for Bering Sea,the temperature of the seawater is 2~3 °C,which is colder than the warm years in 2014 and 2016.Affected by this,the concentration and bioprocessing rate of the Bering Sea Dimethyl Sulfide in 2012 is less than 2014 and 2016,with the exception that the DMSP concentrations of northern Bering Sea shelf in 2012 were greater than 2014 and 2016,possibly due to the freezing protective effect of DMSP.The production rate of dimethyl sulfide is slightly higher than the consumption rate,and the spatial trend of production and consumption rate is consistent.The horizontal distribution trend of DMSO in the Bering Sea is: the Bering Sea Basin < the central of Bering Sea shelf > the northern Bering Sea shelf;the trend of DMSP is: the central of Bering Sea shelf < the Bering Sea Basin < the northern Bering Sea shelf;the horizontal distribution of DMS has no obvious rule.3.In the Bering Sea Basin,the concentration of DMS is the highest in the Bering Sea Basin Upper Water,followed by the Bering Sea Basin Intermediate Water,the lowest in the Bering Sea Basin Deep Water with average concentrations of 5~15,2~8 and 0~1 nmol/L,respectively.In the northern part of the basin,the average concentration of DMSPd is between 2~35 nmol/L,and the average value of DMSPp is between 6~110 nmol/L.The distributions of DMS and DMSPd in Upper and Intermediate Waters are mainly affected by Chl-a.The stress of salinity and temperature have an effect on the distributions of DMS and DMSPd in deep water.In the central Bering Sea shelf,the DMS and DMSP concentrations are higher in the Bering Shelf Surface Water than those in other masses,the concentrations of DMS,DMSPd and DMSPp are in the range of 2~11,20~40 and 27~87 nmol/L,respectively;They are slightly lower in the Bering Slope Current Water and the Mixed Water,with mean values of 0~2,2~40 and 18~78 nmol/L,respectively.Their concentrations in the Bering Shelf Cold Water are the lowest,with mean values of 0~2,1~18 and 14~50 nmol/L,respectively.The controlling factors on DMS and DMSP distributions are very complicated in the surface warm water,the Bering Shelf Cold Water and the Bering Slope Current Water,and they are meanly affected by Chl-a In the Mixed WaterIn the northern Bering Sea shelf,the concentrations of DMS and DMSP are the lowest in Anadyr Water,their concentrations are in the range of 0~3,12~28 and 20~80 nmol/L for DMS,DMSPd and DMSPp,respectively;Their concentrations in Alaska Coastal Water and Bering Shelf Water are higher,with mean values of 1~15,12~47 and 44~120 nmol/L,respectively.The main influencing factors of DMS and DMSP distributions are rather complicated in the Anadyr Water and Alaska Coastal Water.They are meanly affected by salinity and temperature in the Bering Shelf Water.4.The distribution pattern of DMSOd is similar with that of DMSO in the Bering Sea,their concentrations decreased with the increasing of the depth of water.The concentrations of DMSOd and DMSO are greater than 55 nmol/L in the surface water but less than 25 nmol/L in the bottom water.The concentration and distribution of DMSO are mainly controlled by DMS oxidation and phytoplankton synthesis in the Bering Sea Basin,but mainly by biological production in the Bering Shelf Surface Water in the central of Bering Sea shelf.In the northern Bering Sea shelf,the concentration of DMSO is higher in the Alaska Coastal Water and the Bering Shelf Water than in the Anadyr Water.