Phosphorus Regulation of Methane Oxidation in Water From Ice‐Covered Lakes

Winter methane (CH 4 ) accumulation in seasonally ice‐covered lakes can contribute to large episodic emissions to the atmosphere during spring ice melt. Biological methane oxidation can significantly mitigate such CH 4 emissions, but despite favorable CH 4 and O 2 concentrations, CH 4 oxidation appears constrained in some lakes for unknown reasons. Here we experimentally test the hypothesis that phosphorus (P) availability is limiting CH 4 oxidation, resulting in differences in ice‐out emissions among lakes. We observed a positive relationship between potential CH 4 oxidation and P concentration across 12 studied lakes and found an increase in CH 4 oxidation in response to P amendment, without any parallel change in the methanotrophic community composition. Hence, while an increase in sedimentary CH 4 production and ebullitive emissions may happen with eutrophication, our study indicates that the increase in P associated with eutrophication may also enhance CH 4 oxidation. The increase in CH 4 oxidation may hence play an important role in nutrient‐rich ice‐covered lakes where bubbles trapped under the ice may to a greater extent be oxidized, reducing the ice‐out emissions of CH 4 . This may be an important factor regulating CH 4 emissions from high latitude lakes.