Award: PLR-1023444

The Arctic is warming dramatically, with potentially significant impacts on global climate through rapid mobilization of the labile carbon reservoirs that have been sequestered in sediment reservoirs - either permafrost or gas hydrate - for millenia. Dynamic methane cycling in the Arctic ocean drives feedbacks that contribute to climate change by increasing fluxes of the powerful greenhouse gas methane to the atmosphere. Sustained methane release to the atmosphere from thawing Arctic permafrost is a positive and likely significant contributor to the global methane cycle and to global climate change. Additinally, destabilization of methaen hydrate deposits underlying the Arctic seabed could support additional incresaes in methane fluxes. Due to large uncertainties in Arctic methane budgets and a poor understanding of the regulation of methane dynamics in the waters and sediments of the Arctic ocean, predictions of future CH4 emission trends, while critical, are unreliable. This research program evaluated and constrained sediment methane reservoirs and current methane production rates in sediments and water samples and quantified rates of biological methane consumption in sediments and in the water column. We documented low rates of sediment methane production, suggesting only modest present-day contributions to methane inventories in the seabed. Rates of sediment methane oxidation were also modest (~10 nmol/cc/day). Rates of water column aerobic methane oxidation were highest near the mouth of the Lena River and decreased with distance offshore. Pelagic methanotrophy appeared to be nutrient limited and the aerobic methane biofilter was a very inefficient, suggesting that methane released from the seabed could reach the atmosphere due to low rates of microbial consumption. This project supported the professional development and education of a PhD level graduate student, a post doctoral scholar, and a research professional at the University of Georgia. A web site was developed to describe the communicate the research questions and scientific approach of the project (http://www.joyeresearchgroup.uga.edu/research/climate-change/arctic-ecosystems/degrading-offshore-permafrost-source-methane). The project supported several research presentations at national and international conferences and four additional peer-reviewed publications are expected to come out before the summer of 2017. Last Modified: 07/12/2016 Submitted by: Samantha B Joye