Mechanism of the Oxygen-Depleted Water Formation near the Head of the Ariake Bay and its Numerical Modeling

Abstract

A mechanism of the oxygen-depleted water formation near the head of the Ariake Bay is presented based on the field observation data taken by Seikai National Fisheries Research Institute (2009). The first formation of oxygen-depleted water occurred just after big discharges from rivers due to strong salinity stratification and massive Skeletonema sp. growth. The second formation was occurred in August when thermal stratification was developed and Chattonella sp. grew rapidly by taking nutrients in the bottom with vertically migration. A numerical model to simulate these processes was constructed using DELFT3D. The model reproduced the field data very well and revealed that degradation of detritus derived from phytoplankton in the water column and sediment was the most important for the oxygen consumption process.