The Response of Oceanic Dimethylsulfide Fluxes Off the Chinese Coastal Waters to Altered Changjiang (Yangtze) Nutrient Inputs

The Changjiang nutrient inputs serve as an important nutrient source for Chinese coastal waters. Its nutrient flux into the estuary has increased significantly over recent several decades, which may affect regional primary production and the sulfur cycle. Using a well-validated three-dimensional biophysical and geochemical model, we quantified the response of dimethylsulfide (DMS), a biogenic volatile sulfur that could affect the Earth’s climate, to the intensified Changjiang nutrient inputs. The results showed that the enhancement in the oceanic DMS fluxes (F DMS ) exceeded 30% off the coastal waters including the Zhejiang coastal area, the Changjiang estuary, east of the Changjiang estuary, and Subei Shoal given the acceleration in nutrient inputs. In addition, a phenology change in the F DMS was found in the Changjiang estuary and east of the Changjiang estuary. Furthermore, the increase in the F DMS in the Changjiang estuary and Subei Shoal was ascribed primarily to the elevated surface phytoplankton biomass, while the changes in the surface phytoplankton community contributed considerably to the changes in the F DMS in the Zhejiang coastal area and east of the Changjiang estuary. And the sensitivity experiments demonstrated that mainly the elevated Changjiang dissolved inorganic phosphorus inputs led to the increase of the DMS release off these coastal waters. The ratio between the surface concentrations of dissolved inorganic nitrogen ([DIN]) and dissolved silicate ([DSi]) might be a crucial indicator for predicating the surface DMS concentration ([DMS]) under the intensified human activities; a significant positive correlation was found between the change in the surface [DMS] and [DIN]:[DSi] ratio off the coastal area in the East China Sea.