Microbial and Geophysical Insights into the Vulnerability of Permafrost Carbon

Colloquium | November 6 | 3:30-5 p.m. | 575 McCone Hall

 Mark Waldrop, United States Geological Survey (USGS)

 Department of Geography

Northern latitude soils play a critical role in regulating the Earth’s climate through the production and consumption of greenhouse gases. Climate change is predicted to cause widespread permafrost thaw, with a potential release of greenhouse gases that results in a large positive feedback to the climate system. Because these systems are below zero for most of the year, the functioning of microbial communities at or below zero is of paramount importance in order to understand the timing and pathways of greenhouse gas losses from thawing soils. Here we focus on two primary topics: overwinter microbial activities and their importance to net carbon balance of arctic ecosystems, and active microbial communities within intact permafrost near the freezing point when significant liquid water can be present in ice. To elucidate the functioning of microbial communities in permafrost and thawed soils, we utilize geophysical techniques to map variation in the permafrost environment, metagenomics and stable isotope probing to understand the diverse functions of permafrost organisms, and isotope modeling to estimate rates of microbial processes in situ. Results show that microbial activity in winter months is critical to the net carbon balance of arctic ecosystems. We show that microbial communities are active within and below frozen soils, that there are multiple physical and biogeochemical pathways for carbon to be released. These data highlight the fact that microbial communities play a central role in the loss of carbon from thawing permafrost environments, and that multiple unique aspects of permafrost soils allow for novel examination of microbial function.