CREEPIES – Climate relevant effects of microbial predation in eroding soils

Soils host the largest reservoir of carbon and a quarter of biodiversity on Earth. Its microorganisms are invisible to us but are both impacting and impacted by the global climate. Particularly carbon stocks of warming Arctic permafrost, soils frozen even in summer, are thawing, becoming available to those microbes. Some of them, methanogens and methanotrophs, produce and metabolize methane, respectively. They impact how much carbon flows between permafrost and the atmosphere. Their carbon-cycling is impacted by the environment, but also by microbial interactions, such as symbiosis or predation. Especially protists, a diverse group of unicellular microscopic eukaryotes, prey on these soil bacteria. During my PhD research, I found protists abundantly in thawing permafrost, but little is known about them and their ecological role in Arctic soil. With my Villum postdoctoral scholarship, I will elucidate how these predators impact the vulnerable Arctic soil food web, and with that the carbon flow to the atmosphere. I will extract protists from intact permafrost soils, investigate if protist predation is selective for methanogens or methanotrophs, and finally quantify carbon emissions from protist-inoculated permafrost incubations during in vivo artificial thaw. Furthermore, sequencing will facilitate discovery new Arctic protist species and identify their preferred – and potentially carbon balance impacting - prey. These insights will improve predictions on carbon release from the warming Arctic.