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

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Abstract
The effect of hypolimnetic aeration on key components (circulation, decomposition, major nutrients, major ions, and pH interactions) of a lake ecosystem was examined in a small, naturally eutrophic lake. The lake was divided in half with a plastic curtain, and a hypolimnetic aerator was installed and operated 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 O2 concentrations were increased as was O2 consumption since both sediment and water column oxidation of organic material was enhanced. Hypolimnetic NH4+ concentrations were reduced and sufficient O2 was added for nitrification to occur. Internal P loading and hypolimnetic PO43- concentrations were reduced but aerobic P regeneration increased. Aeration vented accumulated CO2 from the hypolimnion and decreased its Ca, Mg, HCO3- and PO43- 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.