Estimation of oxygen consumption rate using T-DO diagram in the benthic layer of Ohmura Bay, Kyushu, Japan

We have observed the temporal variation of oxygen deficient water with short time scale (less than a few days) in the central area of Ohmura Bay, Kyushu, Japan, in summer, 1995 and 1996. The vertical profiles of temperature were similar to those of dissolved oxygen. We noticed a linear relation between temperature and dissolved oxygen in the bottom layer, and applied the T-DO relation to estimate the net oxygen consumption rate, rather than direct evaluation of the advection and diffusion. Oxygen consumption rate just above the bottom was estimated to be about 0.21 g O₂ m^-3day^-1 in July 1995, and about 0.28 g O₂ m^-3day^-1 in August 1996. The net oxygen consumption rate estimated for the bottom layer below the second thermocline was about 0.61 g O₂ m^-2day^-1 with variability from 0.55 to 0.66 g O₂ m^-2day^-1 during July 25 to 29, 1995. This is was about 0.64 g O₂ m^-2day^-1 with variability from 0.18 to 1.4 g O₂ m^-2day^-1 during August 22 to 30, 1996. The nex oxygen consumption rates are about half of those measured with a closed system in the Seto Inland Sea.