Methane emission via sediment and water interface in the Bohai Sea, China.

Sediment is recognized as the largest reservoir and source of methane (CH) in the ocean, especially in the shallow coastal areas. To date, few data of CH concentration in sediment have been reported in the China shelf seas. In this study, we measured CH concentration in sediment and overlying seawater columns, and conducted an incubation experiment in the Bohai Sea in May 2017. CH concentration was found to be ranged from 3.075 to 1.795 μmol/L in sediment, which was 2 to 3 orders of magnitude higher than that in overlying seawater columns. The surface sediment was an important source of CH, while bottom seawater acted as its sink. Furthermore, the net emission rate via sediment water interface (SWI) was calculated as 2.45 μmol/(m∙day) based on the incubation experiment at station 73, and the earthquake may enhance CH release from sediment to seawater column in the eastern Bohai Sea.