These two figures help explain what stratification and turnover are. In the summer and winter, lakes tend to be stratified, where the surface water is a different temperature than the bottom water. Because of that, the lake does not mix completely. In fall and spring, the surface waters either cool off or warm up until they are about the same temperature as the bottom waters. This allows for turnover or mixing of the entire water column. . Turnover is indicated by a straight temperature graph because temperature is fairly uniform. A curved temperature graph, like we found (point) indicates stratification Throughout the summer, Long Pond North was stratified. This lack of mixing kept bottom dissolved oxygen concentrations low and bottom phosphorus levels high. The high bottom phosphorus levels resulted from the anoxia-driven phosphorus release from the sediments.