Oxygen Depletion and Winterkill Risk in Small Prairie Lakes Under Extended Ice Cover

Mean rates of dissolved oxygen depletion in 10 shallow eutrophic prairie lakes (area 2.3–27.3 ha, mean depth 1.6–4.2 m), ranged from 0.22 to 0.34 g/m 2 ∙d −1 for nonstratified lakes and 0.32–0.42 g/m 2 ∙d −1 for stratified ones. An average rate for all lakes was 0.29 ± 0.06 g/m 2 ∙d −1 . The rates correlated with the lake depth. A method for estimating the winterkill risk on the basis of initial oxygen storage, rate of dissolved oxygen depletion and/or the mean or maximum lake depth is proposed. Key words: prairie lakes, oxygen depletion rates, winter fish kill, eutrophication, metabolism, oxygen storage