Abstract
Quality of water and sediments (Eh, organic matter and hydrogen sulfide) were investigated every week in order to clarify the short-term variations in the inner western area of Ariake Bay. The physical replenishment (stratification) due to the freshwater input and high density water intrusion casused hypoxia, and meteorological effects, vertical mixing due to the wind including the typhoon, was made hypoxia vanish. Hydrogen sulfide of high concentration was generated in the situation of development of hypoxia, and the concentration was decreased due to the wind specially. The area of low Eh (-180mV) corresponded with that of high concentration of hydrogen sulfide. The increase of mortality of ark clam (Scapharca subcrenata) toward the end of July was caused by hypoxia and generation of hydrogen sulfide under low pH (about 7.2) in the sediments due to the decomposition of organic matter.
