An unstable density field is formed near the bottom of Kaita Bay. It is predicted that the unstable density field is kept by density increment from suspended organic mud. In order to understand the property and behavior of suspended organic mud, relationship among of settling time, diameter and composition was investigated. Furthermore, density increment from suspended organic mud is confirmed. As a result, it is cleared that property of slowly suspended organic mud is small diameter and low C/N ratio. Additionally, density increment of suspended organic mud is bigger than that of soil particle.
