Interdisciplinary study on the thermohaline front at the mouth of Tokyo Bay in winter

Abstract

An intensive field observation was carried out around the thermohaline front at the mouth of Tokyo Bay in order to reveal the physical, chemical and biological characteristics of a thermohaline front. The low water temperature, low salinity, nutrient-rich and high chlorophyll a coastal water and the high water temperature, high salinity, nutrient-poor and low chlorophyll a offshore water converge at the thermohaline front in the surface layer, mix there and sink downward. Some mixed water intrudes into the intermediate layer of offshore water and the other flows into the bottom layer of coastal water like a shirt. The density of fish larvae is higher in coastal water than in offshore water and the highest at the front. On the other hand, the density of copepods is higher in offshore water than in coastal water. The concentration of dissolved oxygen is low near the front due to the respiration of large biomass which are accumulated in the surface layer of the front.