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

Sediment is recognized as the largest reservoir and source of methane (CH₄) in the ocean, especially in the shallow coastal areas. To date, few data of CH₄ concentration in sediment have been reported in the China shelf seas. In this study, we measured CH₄ concentration in sediment and overlying seawater columns, and conducted an incubation experiment in the Bohai Sea in May 2017. CH₄ 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 CH₄, while bottom seawater acted as its sink. Furthermore, the net emission rate via sediment water interface (SWI) was calculated as 2.45 μmol/(m²∙day) based on the incubation experiment at station 73, and the earthquake may enhance CH₄ release from sediment to seawater column in the eastern Bohai Sea.