Freshwaters live at the interface of terrestrial and aquatic ecosystems and therefore are some of the most productive places on Earth. One of the consequences of being highly productive and receiving large quantities of organic matter from surrounding landscapes is that freshwaters can be among the largest atmospheric sources of two terminal gases from microbial metabolism, carbon dioxide and methane (CH4). Methane is produced primarily in anoxic or hypoxic environments but in stratified systems with atmospheric exposure, most of the CH4 is oxidized before it reaches the atmosphere, leading to a significant dissolved oxygen (DO) demand in ponds and lakes. DO loss from lakes is a global phenomenon and is particularly problematic in deep Minnesota lakes with coldwater fisheries. We examined methane-induced DO demand in a variety of Minnesota lakes with varying stratification patterns from holomictic lakes that were polymictic to dimictic as well as several meromictic lakes. We estimated DO-demand from profiles of DO and CH4 assuming only diffusive losses of CH4. These estimates indicated that from 15-100% of DO demand could be due to CH4 oxidation with the highest values typically observed in the most strongly stratified systems with the highest CH4 concentrations. Climate change is leading to stronger and longer stratification in lakes globally which means that ecosystem managers need to focus on CH4 both as a driver of climate change but also as an important water quality parameter.