Methane (CH4) is an important greenhouse gas and oceans are net sources of atmospheric CH4. The effects of environ- mental factors on the CH4 variation during different phases of the spring algal blooms were examined ...Methane (CH4) is an important greenhouse gas and oceans are net sources of atmospheric CH4. The effects of environ- mental factors on the CH4 variation during different phases of the spring algal blooms were examined during two cruises conducted in the Yellow Sea (YS) from February to April of 2009. During the pre-bloom period from February to March, low CH4 saturation (< 134%) was observed in the surface water, except at two nearshore stations where the CH4 levels were above 140% in March due to mixing with the coastal water. During the bloom period, CH4 increased obviously at two bloom-tracking stations, especially at the surface with mean saturations of 140% and 170%. The increase in CH4 concentration/saturation is thought to be the result of in situ CH4 production. The particulate organic carbon (POC) and chlorophyll a contents were believed to be important factors that influ- enced the CH4 production. In addition, the presence of different dominant phytoplankton species and the grazing pressure may have stimulated the CH4 production by supplying potential methanogenic substrates (such as dimethylsulphoniopropionate (DMSP)). Both the incubation data and the in situ estimations further evidenced the significant influence of the spring blooms on the CH4 production. The calculated sea-to-air CH4 fluxes during the bloom period were not significantly higher than those during the pre-bloom period despite the bloom-increased CH4 saturation. This is due to the variation in physical forcing (such as wind speed), which is the main driver for determining the CH4 flux. Finally, we estimated the annual CH4 flux in the YS as 9.0 μmol m 2 d 1;the findings suggest that the YS is a natural source of atmospheric CH4.展开更多
Knowledge about the distribution of CH_(4)remains insufficient due to the scarcity of data in the Arctic shelves.We conducted shipboard observations over the Chukchi Sea shelf(CSS)in the western Arctic Ocean in Septem...Knowledge about the distribution of CH_(4)remains insufficient due to the scarcity of data in the Arctic shelves.We conducted shipboard observations over the Chukchi Sea shelf(CSS)in the western Arctic Ocean in September 2012 to obtain the distribution and source characteristics of dissolved CH_(4)in seawater.The oceanographic data indicated that a salinity gradient generated a pronounced pycnocline at depths of 20-30 m.The vertical diffusion of biogenic elements was restricted,and these elements were trapped in the bottom waters.Furthermore,high CH_(4)concentrations were measured below the pycnocline,and low CH_(4)concentrations were observed in the surface waters.The maximum concentrations of nutrients simultaneously occurred in the dense and cold bottom waters,and significant correlations were observed between CH_(4)and SiO_(3)^(2-),PO_(4)^(3-),NO_(2)^(-),and NH_(4)^(+)(p<0.01,n=44).These results suggest that the production of CH_(4)in the CSS has a similar trend as that of nutrient regeneration and is probably associated with the degradation of organic matter.The high primary productivity and high concentration of organic matter support the formation of biogenic CH_(4)in the CSS and the subsequent release of CH_(4)to the water column.展开更多
基金funded by the Ministry of Science and Technology of China (No. 2016YFA0601302)the National Natural Science Foundation of China (No. 41521064)+1 种基金supported by the Taishan Scholars Program of Shandong Provincethe Aoshan Talents Program of the Qingdao National Laboratory for Marine Science and Technology (No. 2015ASTP-OS08)
文摘Methane (CH4) is an important greenhouse gas and oceans are net sources of atmospheric CH4. The effects of environ- mental factors on the CH4 variation during different phases of the spring algal blooms were examined during two cruises conducted in the Yellow Sea (YS) from February to April of 2009. During the pre-bloom period from February to March, low CH4 saturation (< 134%) was observed in the surface water, except at two nearshore stations where the CH4 levels were above 140% in March due to mixing with the coastal water. During the bloom period, CH4 increased obviously at two bloom-tracking stations, especially at the surface with mean saturations of 140% and 170%. The increase in CH4 concentration/saturation is thought to be the result of in situ CH4 production. The particulate organic carbon (POC) and chlorophyll a contents were believed to be important factors that influ- enced the CH4 production. In addition, the presence of different dominant phytoplankton species and the grazing pressure may have stimulated the CH4 production by supplying potential methanogenic substrates (such as dimethylsulphoniopropionate (DMSP)). Both the incubation data and the in situ estimations further evidenced the significant influence of the spring blooms on the CH4 production. The calculated sea-to-air CH4 fluxes during the bloom period were not significantly higher than those during the pre-bloom period despite the bloom-increased CH4 saturation. This is due to the variation in physical forcing (such as wind speed), which is the main driver for determining the CH4 flux. Finally, we estimated the annual CH4 flux in the YS as 9.0 μmol m 2 d 1;the findings suggest that the YS is a natural source of atmospheric CH4.
基金supported by the Scientific Research Foundation of the Third Institute of Oceanography, MNR (Grant nos. 2022011, 2018031 and 2018024)the Natural Science Foundation of Fujian Province, China (Grant no. 2020J01102)
文摘Knowledge about the distribution of CH_(4)remains insufficient due to the scarcity of data in the Arctic shelves.We conducted shipboard observations over the Chukchi Sea shelf(CSS)in the western Arctic Ocean in September 2012 to obtain the distribution and source characteristics of dissolved CH_(4)in seawater.The oceanographic data indicated that a salinity gradient generated a pronounced pycnocline at depths of 20-30 m.The vertical diffusion of biogenic elements was restricted,and these elements were trapped in the bottom waters.Furthermore,high CH_(4)concentrations were measured below the pycnocline,and low CH_(4)concentrations were observed in the surface waters.The maximum concentrations of nutrients simultaneously occurred in the dense and cold bottom waters,and significant correlations were observed between CH_(4)and SiO_(3)^(2-),PO_(4)^(3-),NO_(2)^(-),and NH_(4)^(+)(p<0.01,n=44).These results suggest that the production of CH_(4)in the CSS has a similar trend as that of nutrient regeneration and is probably associated with the degradation of organic matter.The high primary productivity and high concentration of organic matter support the formation of biogenic CH_(4)in the CSS and the subsequent release of CH_(4)to the water column.
