Lakes in temperate regions of the world follow a seasonal cycle: winter ice cover and inverse stratification where the warmest water is near the bottom and the coolest is at the top, a period after the ice melts called spring turnover when the lake is mixing from top to bottom, summer stratification when the lake establishes a warm top layer and a cold deep layer, and fall turnover when the lake mixes and is uniform from top to bottom.
The August 19, 2010 temperature and dissolve oxygen readings shows the lake is in summer stratification. A strong thermocline has been established between the depths of 10 m. (32.5 ft) and 14 m (45.5 ft). The thermocline seperates the upper circulating warm layer of the lake’s epilimnion from the deep cold waters of the hypolimnion. The epilimnion exists from the lake’s surface to a depth of 9 m (29.3 ft). The hypolimnion exists from 15 m. (48.8 ft) to the measured bottom at 42 m. (136.5 ft.)
Surface temperature was at 26.2 o C (79.2 0 F) with the bottom of the epilimnion being at a temperature of 24.7o C (76.5o F). Temperature dropped rapidly in the thermocline with the top of the thermocline being at 21.10 C (70.00 F) and the bottom at 12.90 C (55.20 F). Within the thermocline depth of 5 meters (16 ft) the temperature of the water dropped 12.20 C (14.80 F) or about 30 F per meter.
The thermocline will continue to be eroded or compressed till fall when cooling surface waters reach the same temperature as the thermocline. This will cause the thermocline to disappear. The lake will then enter into fall turnover where temperature and dissolved oxygen are uniform from the top waters of the lake to the bottom waters. The lake then mixes from top to bottom.
At the lake’s surface dissolved oxygen concentration is 8.48 mg/l. It drops to 7.42 mg/l at the bottom of the epilimnion,10m (32.5 ft). Dissolved oxygen increases slightly within the hypolimnion for about four meters and then decreases all the way to the bottom.
At a depth of 28 m (91 ft) oxygen levels drop below 54.0 mg/l. At 30 m ( 97.5 ft) oxygen levels drop below 2.0 mg/l. Fish experience higher levels of stress when dissolved oxygen levels drops below 5 mg/L. Most fish species can not survive for any period of time where dissolved oxygen is less than 2 mg/L.