The Hydrographic Conditions and the Fisheries Damages by the Red Water Occurred in Omura Bay in Summer 1965―III.The Oceanographic Conditions in the Offing Region of Omura Bay during the Term of the Red Water

摘要

There was observed a distinctive character in the oceanographic conditions of Omura Bay during the term of red water that the dissolved oxygen in the bottom water mass was remarkably lower in summer 1965 than in any past year. It is not clear how the occurrence of the red water was connected with the distribution of low dissolved oxygen, but the authors assume that the occurrence of low oxygen was caused, as follows. (1) The water mass lacking in dissolved oxygen occurred owing to the rising of water temperature, to the extension of thermocline by rainfall and to the stagnation of water mass by semiclosure, such being natural status of Omura Bay. (2) The degree of low dissolved oxygen was intensified by the decay and decomposition of the red water planktons which extraordinarily increased on the bottom layer.