Methane fueled lake pelagic food webs in a Cretaceous greenhouse world

What is it about?

Lakes are hotspots of microbial methane (CH4) cycling that has implications for both lake food webs and greenhouse gas emissions. Current CH4 dynamics in lakes have been well documented; however, in the geological record the processes remain poorly constrained, and linking CH4 to food webs is a challenge. Here we report the existence of CH4-fueled lake pelagic food webs during the Cretaceous Oceanic Anoxic Event 1a (~120 million years ago), showing a major expansion of both methanogens and CH4-oxidizing bacteria and an accelerated carbon and energy flow from CH4 to the higher trophic levels. Our findings point to an understudied pathway by which microbial CH4 dynamics can restructure food webs and impact carbon cycling in lake ecosystems under climate warming.

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Photo by John Bakator on Unsplash

Photo by John Bakator on Unsplash

Why is it important?

Carbon dioxide (CO2) and sunlight captured through photosynthesis effectively provide carbon and energy that flow upwards through food webs. Alternatively, methane (CH4) is an important but often neglected source of carbon and energy in lake ecosystems. In this study, we provide evidence for enhanced lacustrine CH4 cycling during the Cretaceous Oceanic Anoxic Event 1a (OAE 1a; ~120 million years ago), demonstrating that CH4-derived carbon was transferred to higher trophic levels and contributed to lake pelagic food webs.