Climate-driven shifts in sediment chemistry enhance methane production in northern lakes

Freshwater ecosystems are a major source of methane (CH(4)), contributing 0.65 Pg (in CO(2) equivalents) yr(−1) towards global carbon emissions and offsetting ~25% of the terrestrial carbon sink. Most freshwater CH(4) emissions come from littoral sediments, where large quantities of plant material are decomposed. Climate change is predicted to shift plant community composition, and thus change the quality of inputs into detrital food webs, with the potential to affect CH(4) production. Here we find that variation in phenol availability from decomposing organic matter underlies large differences in CH(4) production in lake sediments. Production is at least 400-times higher from sediments composed of macrophyte litter compared to terrestrial sources because of inhibition of methanogenesis by phenol leachates. Our results now suggest that earth system models and carbon budgets should consider the effects of plant communities on sediment chemistry and ultimately CH(4) emissions at a global scale.