Abstract
Usinga numerical model,we reproduced an oxygen-depleted watermass that occurredduring
the summer in 1991, in Ise and Mikawa bay that comprise one of the most eutrophic estuaries in
Japan. The most severely oxygen-depleted water mass appeared in the middle-basin of Ise bay
and the inner-part of Atsumi bay, located in the east of Mikawa bay.
In these areas, particulate organic matter accumulated due to oceanographic features such as
horizontal circulation in the upper-layer and down-welling on the off-shore sides. The latter fea
ture ultimately obstructed the supply of dissolved oxygen to the inner-areas of the bays.
Carbon cycle and dissolved oxygen budgets for the bottom layer were calculated for these
oxygen depleted areas. We found that bottom mud consumed the most oxygen (45-66%), fol
lowed by the degradation of particulate organic matter from the upper-layer (21~35%).
Using this numericalmodel, we evaluated the feasibility of improvingtechnology to increase
the dissolved oxygen content of water mass for these two areas. The calculation was based on the
assumption that the upper water rich in dissolved oxygen was supplied to the bottom layer. The
calculations were conductedin these cases.A supplement at 100m^3/min, that was the most biggest
in realizablescale, slightly increasedthe dissolvedoxygenconcentration but was not sufficient to
a low recovery of the macrobenthos community.
