B41C-0447
Examining the Role of Aquatic Vegetation in Methane Production: Examples From a Shallow High Latitude Lake in Abisko, Sweden.
Thursday, 17 December 2015
Poster Hall (Moscone South)
Christopher Daniel Horruitiner1, Ruth K Varner2, Michael W Palace2, Joel E Johnson3, Martin Wik4, Dylan J Lundgren3, Samantha Noelle Sinclair3, Adam Jacob Donnally Nicastro5 and Maurice Crawford6, (1)University of Florida, Ft Walton Beach, FL, United States, (2)University of New Hampshire Main Campus, Durham, NH, United States, (3)University of New Hampshire Main Campus, Earth Sciences, Durham, NH, United States, (4)Stockholm University, Dept. of Geological Sciences, Stockholm, Sweden, (5)Miami University Oxford, Oxford, OH, United States, (6)University of Maryland Eastern Shore, Department of Natural Sciences, Princess Anne, MD, United States
Abstract:
High latitude lakes and ponds are a large source of atmospheric methane. Emissions from lakes are thought to be controlled primarily by temperature and secondarily by the availability of labile organic carbon. Aquatic plants provide insitu carbon sources to lake bottoms and therefore can potentially impact rates of methane production. We studied vegetation and lake sediment characteristics across shallow depths in Inre Harrsjön, a lake located within the Stordalen Mire in the discontinuous permafrost zone in subarctic Sweden. Vegetation surveys using a submerged quadrat with camera were performed in transects across IH to characterize bottom vegetation. Carbon and nitrogen elemental analysis was performed on vegetation samples from both the lake and surrounding mire ecosystem. Sediment cores representing each vegetation type were analyzed for CH4, δ13CH4, and elemental CHNS. In all cores but one, total organic carbon (TOC) is greatest near the surface and decreases downcore. Methane concentrations correlated with TOC indicating insitu methane production. C:N ratios in sediment cores are more reflective of aquatic than terrestrial mire vegetation indicating that organic carbon in the lake sediments is dominated by aquatic sources. δ13CH4 is relatively constant downcore, which indicates little to no methane oxidation. The methane produced in sediments is consistently within the range of hydrogenotrophic methanogenesis via CO2 reduction. We suggest the role of aquatic vegetation in the production of methane in high latitude shallow lakes may be important and will likely have a positive feedback in a warming climate with longer ice-free seasons.
