DEPENDENCE OF LAKE OXYGEN DEPLETION RATES ON MAXIMUM OXYGEN STORAGE IN A PARTIALLY MEROMICTIC LAKE IN ALBERTA

Areal rates of hypolimnetic oxygen depletion (AHOD) and winter oxygen depletion (AWOD) varied considerably from year to year in a partially meromictic lake (Narrow Lake) in central Alberta. AHOD ranged from 0.222 to 0.522 g O2 .cntdot. m-2 .cntdot. d-1 over four summers and AWOD ranged from 0.354 to 0.614 g O2 .cntdot. m-2 .cntdot. d-1 over three winters. AHOD was positively correlated with maximum storage of dissolved oxygen (O2) at the onset of summer thermal stratification (P < 0.05). Similarly, AWOD was higher in years when mixing was more complete and maximum O2 storage at freeze-up was higher. These results suggest that the prediction of O2 depletion rates for lakes with year-to-year variation in maximum O2 storage can be improved if maximum O2 storage after lake mixing is considered in addition to other factors known to influence O2 depletion rates such as lake productivity and morphometry.