Diverse methane concentrations in anoxic brines and underlying sediments, eastern Mediterranean Sea

Abstract

Elevated methane (CH sub(4)) concentrations (128-2692x10 sup(3) nM) occur in the hypersaline anoxic brine pools of Bannock and Urania Basins, eastern Mediterranean Sea, compared to low concentrations (17-80x10 sup(3) nM) in the sediments below the anoxic brines. The CH sub(4) enrichment in the brines might be due to the long residence time of the brine in the Basin. An attempt is made to determine the source for the enriched dissolved CH sub(4) by considering the influence of hydrothermal activity, the occurrence of sapropel alyers (biogenic) and dissolution of gas hydrates. Furthermore, it is suggested that the enriched CH sub(4) in Bannock and Urania Basins is diffused and mixed with the overlying waters by local upward transport mechanisms that selectively move CH sub(4) upward in these Basins