Carbon dioxide and methane are the two most concerning greenhouse gases in terms of their effects on warming our planet. Freshwaters are an important source of these gases, especially methane. Fortunately, most of the methane that is produced in freshwaters is converted to the less potent carbon dioxide by microbes before it is released to the atmosphere, a process defined as methanotrophy. Unfortunately, methanotrophy is oxygen costly which can be in short supply in some of the deeper regions of lakes. Most lakes are dimictic, with seasonal lake turnover replenishing oxygen throughout the water column. However, some lakes are meromictic and don’t completely mix, with the deepest waters remaining stratified. One of the manifestations of climate change is stronger and longer lake stratification which limits the exchange of oxygen with the atmosphere facilitating increased methane production in lakes and possibly less conversion to carbon dioxide. Methane is one of the most labile organic carbon substrates to microbes in lakes and it also has the lowest respiratory quotient (RQ) of any organic compound further depleting oxygen. Here, we 1) quantify microbial RQs and 2) evaluate the significance of methanotrophy as a sink for dissolved oxygen in lakes and ponds in Minnesota with varying mixing patterns. Over the course of a 30-day incubation, dissolved oxygen decreased rapidly as highly labile carbon was consumed, shifting the carbon pool towards more recalcitrant composition signatures over time. Preliminary results suggest that in lakes with higher methane concentrations, especially meromictic lakes, the RQs are consistent with anaerobic processing of reduced carbon, indicating the importance of methanotrophy in these systems.