The distribution of methane in the Tōkyō-wan

Eleven stations were occupied in the Tōkyō-wan during a study on the distribution of methane in this autrophic coastal environment in August of 1993.The principal features of the observed methane included the following 6 points: (1) Excess methane in the surface layer from 1.5 times to greater than 25 times solubility equilibrium with the atmosphere. (2) The methane concentration in the upper water displayed a maximum wne around Station 5 and the second highest in bottom water at Stations 1 and 2, probably because there was the front resulting from the chemical processes. (3) Cotrelations between methane and other parameters exhibited correspondences and the methane distribution being mainly controlled by physical processes. (4) In some' stations, vertical profiles revealed associations between methane and Chl a and the relationships between methane with Chl a or nitrite have shown good linear cortelations.It is postulated that some methane is formed in situ. (5) The calculated flux of methane acrbss the air-sea interface was about 71 μmol/(m²·d). (6) Some methane might be produced along with the organic matter decomposition in bottom water.Others might be due to the methane fluxes into the bottom water from the anoxic sediment inside the bay, which are believed to be the main methane source.