The Meromixis of Sunfish Lake, Southern Ontario

In the meromictic Sunfish Lake the large populations of phytoplankton that are observed periodically were associated with circulation of the mixolimnion. Perhaps some organic dissimilation took place in the lower mixolimnion, recycling nutrients during spring and fall circulation. Phytoplankton was practically absent from the epilimnion during the summer but a population of Oscillatoria agardhii remained in the metalimnion, where it was responsible for a pronounced and persistent metalimnetic oxygen maximum. The monimolimnion contained about 5100 mg/liter of dissolved solids and the upper mixolimnion about 2200 mg/liter. Ventilation of the monimolimnion did not always coincide with circulation and subsurface springs may have been responsible. Circulation to the lake bottom was observed only once in 18 months.