epilimnion

…the upper water layer (the epilimnion) and the lower water layer (the hypolimnion) of lakes. The starting point is photosynthesis, represented by the following reaction:

…as the surface water (epilimnion) warms and ceases to mix with the lower, colder layer (hypolimnion). Water circulates within but not between the layers, more vigorously within the epilimnion. The boundary between these layers is the metalimnion, a zone of rapid temperature change. With the onset of autumn, the…

…the upper mixed layer (epilimnion) and the deep portion of the lake (hypolimnion). In shallow lakes or shallow portions of large lakes, the thermocline will eventually intercept the lake bottom so that no hypolimnion exists. Normally, as the heating season progresses, the thermocline intensifies and deepens. Secondary thermoclines may…