Dissolved oxygen status of Lake Winnipeg: Spatio-temporal and isotopic (δ18O-O2) patterns

► Spatio-temporal patterns of dissolved oxygen and its δ18O were obtained between 2006-2010 at over 50 stations in Lake Winnipeg, Canada, to determine dissolved oxygen status and aquatic community metabolic balance under current eutrophic conditions. ► Spatial patterns of dissolved oxygen and δ18O modeling showed that Lake Winnipeg is largely net heterotrophic (R:P > 1.1) and under-saturated in oxygen despite high nutrient loading and recurring phytoplankton blooms. ► Surface water oxygen super-saturation and bottom water hypoxia were tempered due to the shallow, well-mixed, and highly turbid nature of the lake. Transient bottom water dissolved oxygen depressions occurred within a < 1 m thick hypolimnion in the North Basin in summer and winter. ► The use of spatio-temporal dissolved oxygen mapping and isotopic assays provided a snapshot of the current dissolved oxygen and metabolic conditions and a productivity benchmark by which to compare the outcome of future nutrient management developments in Lake Winnipeg's contributing watersheds.