Stratified Condition of Lake Kaiike, a Small Coastal Lake on Kamikoshiki Island, Kagoshima Prefecture

Abstract

Vertical distributions of chlorinity, water temperature, dissolved oxygen and hydrogen sulfide have been obtained from Lake Kaiike, a small coastal lake on Kamikoshiki Island, Kagoshima Prefecture, during April, 1976 and October, 1977. Lake Kaiike (surface area : 0.15 km2; maximum depth : 11.6 m) is stratified between brackish water layer above (chlorinity, 6.6-12.2 ‰) and saline layer below (chlorinity, more than 17 ‰). During the spring and autumn, high temperature of up to 39°C were found in the boundary. In the lower water layer an anoxic condition prevailed throughout the year and a noticeable amount of hydrogen sulfide was contained. From autumn to winter the lake was exposed to wind-induced mixing process and the stratified condition was somewhat altered. With the gradual rise of sea level during spring to summer seawater intruded into the bottom by seepage through the gravel bar.