Abstract
Lake Ogawara is a brackish lake, which is located in southeast side of Aomori prefecture. In past researches, it is known that the water depth of the halocline in the lake has become shallow. The volume of anoxic water has increased in the lake, and the boundary area has increased in proportion. Therefore, they have influenced the habitat of fish, shellfish and eutrophication of the lake. In this study, it was discussed that the relationship between halocline and water quality in the lake. Furthermore, it was tried to clarify the relationship between the water quality and the vertical position of halocline by the vertical distribution of water quality. According to the vertical distribution of salinity, the depth of halocline has become shallow. The vertical distribution of DO shows that the values in August begin to decrease from the depth of deeper than thermocline. In December, the values of DO begin to decrease from the depth of deeper than halocline. The values of COD increase gradually in the lower layer.
