Genomic Science Program
U.S. Department of Energy | Office of Science | Biological and Environmental Research Program

Influence of Temperature on Arctic Lake Sediment Methane Production and Organic Matter Composition

Authors:

McKenzie Kuhn1,2* (mckenzie.kuhn@unh.edu), Cheristy Jones1,2, Clarice Perryman3, Nikki Castro-Morales1,2,4, K. De Leon4, C. Beezely4, Malak Tfaily5, Rachel Wilson6, Jeffrey Chanton6, F. Li7, Virginia Rich7, Ruth K. Varner1,2

Institutions:

1Department of Earth Sciences, University of New Hampshire; 2Institute for the Study of Earth, Oceans, and Space, University of New Hampshire; 3Department of Earth Systems Science, Stanford University–Palo Alto; 4EMERGE Research Experience for Undergraduates, University of New Hampshire; 5Department of Environmental Science, University of Arizona; 6Department of Environmental Chemistry and Ecology, Florida State University; 7Department of Microbiology, The Ohio State University

Abstract

Arctic lakes are important sources of methane (CH4) into the atmosphere. CH4 emissions from lakes are expected to increase as the Arctic warms due to increasing microbial activity and greater availability of more labile organic matter substrates. However, the effect of temperature on the sensitivity of different CH4 production pathways and on the chemical composition of lake sediments remains understudied. In this project, researchers used incubations to measure the temperature sensitivity of sediment CH4 production and sediment organic matter composition and diversity. CH4 production increased exponentially with temperature across sediments from the edge and center of two lakes. Stable carbon (C) isotopic signatures of CH4 and CO2 suggest evidence of greater contribution of acetoclastic methanogenesis as opposed to hydrogenotrophic methanogenesis with increasing temperature, but the influence of anaerobic CH4 oxidation on observed isotope signatures cannot be ruled out. CH4 production was positively correlated with organic compounds that contained C, hydrogen, oxygen, nitrogen, and sulfure elemental compounds (r2 = 0.32, P <0.01). Further, the functional diversity (Rao’s quadratic entropy) of elemental composition of sediment porewater was negatively correlated with activation energy derived from incubations, suggesting less elementally diverse sediments are more sensitive to temperature changes, despite the more elementally diverse sediments having higher production rates overall. The preliminary results highlight the complex interactions between organic matter diversity and CH4 cycling and pending microbial data (metaG and metaT analysis) will provide greater insights.