Methane efflux and oxidation, and use of methane-derived carbon by larval Chironomini, in arctic lake sediments

We measured sediment methane (CH4) efflux and CH4 oxidation in intact sediment cores from 17 arctic Alaskan lakes which varied in lake area and depth. We evaluated the relationships between CH4 oxidation and lake area, depth, and hypolimnetic dissolved oxygen (DO). We also evaluated the relationship between delta C-13 of larval Chironomini and CH4 oxidation and estimated use of methane-derived carbon (MDC) by larval Chironomini. CH4 oxidation declined exponentially as hypolimnetic DO increased, and Chironomini C-13 declined exponentially as CH4 oxidation increased. Mixing model estimates indicated that Chironomini incorporated 0% to 40% MDC between study lakes, dependent on CH4 oxidation. These estimates overlap broadly with those reported for eutrophic lakes, illustrating that use of MDC is not strictly related to lake productivity, but instead is determined by factors controlling hypolimnetic DO and facilitating CH4 oxidation at the sediment-water interface. In the lakes studied here, hypolimnetic DO was determined by basin characteristics. Our results, viewed in the context of other studies elsewhere, illustrate that CH4 oxidation is a potentially important process supporting consumer production across the full spectrum of lake productivity.