32P introduced into the surface water can be traced through the thermocline into the deeper water. The movement indicates that the sinking of plankton and particles carries nutrients downward from the surface waters, as in the open ocean. 32P has also been released from a bottle exploded in the deeper water to observe its spread there. In one experiment the 32P was found to move about 3 meters per day in the deeper water, but to show little movement through the thermocline into the surface water. From the deeper water the 32P can be traced into the mud by settling of particles and uptake by bacteria and other organisms in the mud. Some •S2P is released back from the mud into the water. The amount moving back in this way is less than that moving into the mud, however, so that there is progressive net accumulation of 32P in the mud. This 32P accumulation and turnover in the mud is affected by the oxygen content of the deeper water. When free oxygen is present, the phosphorus is more effectively removed from the water and held in the mud than when free oxygen is lacking.