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Surface Ocean and Lower Atmosphere Study—Air-Sea interactions and their climatic and environmental impacts
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Distribution and Biogeochemical Cycling of Dimethylsulfide in the Yellow Sea and the Bohai Sea During Spring
P-C4-10-S
Feng XU* , Ocean University of China
Xiao-Yan CAO* , Ocean University of China
Presenter Email: xufeng00@foxmail.com |
| Marine dimethylsulfide (DMS) is the prevailing volatile sulfur compound of the biological sulfur cycle in the ocean, which can indirectly impact Earth's radiation balance by their major oxidation products in the atmosphere, scattering solar radiation, ultimately, inducing the global climate change. In this research, the spatial distributions of three biogenic sulfur compounds, including DMS, dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) were determined in the Yellow Sea (YS) and the Bohai Sea (BS) during April-May 2014. Besides, in situ incubation experiments were emphatically simulated on board at 12 selected stations, to study the production, migration and transformation processes of DMS. The concentrations of chlorophyll a (Chl-a) and DMS were ranged from 0.20 to 5.83 μg L-1 and from 1.08 to 16.45 nmol L-1, with mean values of 1.57 μg L-1 and 5.95 nmol L-1 respectively. The average concentrations (min-max) of particulate DMSP (DMSPp), dissolved DMSP (DMSPd), particulate DMSO (DMSOp) and dissolved DMSO (DMSOd) were 21.34 (5.06-37.39), 6.03 (1.62-19.81), 14.70 (1.90-47.06) and 17.08 (4.50-44.87) nmol L-1, respectively. The concentrations of DMS and DMSP were significantly correlated with the stocks of Chl-a even under complex hydrographic conditions, presenting a downward trend from the inshore to the offshore. In situ incubation experiments manifested that the average rates (min-max) of DMS gross production and DMSPd degradation were calculated to be 11.67 (7.05-16.27) and 19.62 (13.33-28.23) nmol L-1 d-1, which suggested that only approximately half of degraded DMSPd were translated to DMS. The mean rates (min-max) of DMS microbial consumption and photochemical oxidation were 6.15 (2.35-9.36) and 7.15 (2.30-16.93) nmol L-1 d-1. The biological production was too insufficient to maintain the internal sink of DMS. Vertical transport input from the underlying water may be another source of DMS in surface seawater. The turnover times of microbial consumption, photochemical oxidation and sea-to-air exchange were determined to be 1.53, 1.16 and 1.42 d-1, respectively, which contributed 31.4%, 31.7% and 36.9% of total DMS removal. Simultaneously, the radiation experiments stated that the photolysis under UVB, UVA and visible light accounted for 23.9%, 71.8% and 4.3% of the total photolysis, respectively. Additionally, the sea-to-air fluxes of DMS were estimated to from 0.24 to 34.11 μmol m-2 d-1, with a mean of 8.84 μmol m-2 d-1 and preliminary calculation of average annual release of DMS from the study area to atmosphere reached 0.0472 Tg S a-1, which indicated that the DMS emission from the YS and the BS to the atmosphere was not negligible given the investigation area proportion of the global ocean area. |
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