Hypolimnetic Aeration of A Naturally Eutrophic Lake: Physical and Chemical Effects

Abstract

To examine the effect of hypolimnetic aeration on key components (circulation, decomposition, major nutrients, major ions, and pH interactions) of a lake ecosystem, I used a small naturally eutrophic lake. I divided the lake in half with a plastic curtain, and installed and operated a hypolimnetic aerator in the experimental half for a year. Hypolimnetic aeration had no effect on thermal stratification during the ice-free season but circulated the entire experimental half under ice cover. Aeration increased hypolimnetic turbidity via reduced detrital sedimentation but did not affect epilimnetic transparency. Hypolimnetic oxygen concentrations were increased as was oxygen consumption as both sediment and water column oxidation of organic material was enhanced. Hypolimnetic ammonia concentrations were reduced and sufficient oxygen was added for nitrification to occur. Internal phosphorous loading and hypolimnetic orthophosphate concentrations were reduced but aerobic P regeneration increased. Aeration vented accumulated CO2 from the hypolimnion and decreased its calcium, magnesium, bicarbonate, and orthophosphate content via calcium carbonate phosphate coprecipitation. Management applications of hypolimnetic aeration include reduction of internal nutrient loading for eutrophication control, improvement of water quality for domestic use, and prevention of fish winterkill.