Centre Eau Terre Environnement
490, rue de la Couronne
The rapid climate warming in Arctic regions has induced extensive permafrost thawing and the consequent mobilization of a large reservoir of organic carbon that was frozen for millennia. Although the release of this old carbon into the atmosphere, either as carbon dioxide (CO2) or methane (CH4), may act as a positive feedback mechanism to global warming, the knowledge on patterns and rates of the biochemical processes involved as the different carbon pools are becoming available to aquatic ecosystems is rather scarce. As part of an interdisciplinary project investigating the influence of geomorphological and limnological factors on greenhouse gas (GHG) emissions from lakes and ponds on Bylot Island, Nunavut, my study aims to determine the lability (decomposability) and accessibility of the different carbon pools to microorganisms, and how this links to GHG emissions. The variability in carbon pool lability is one of the main gaps identified in recent studies on the vulnerability of permafrost carbon pools to climate warming.
The study was started in 2014 with incubation experiments on four sediment types found in organic-rich polygonal patterned ground landscape: upper-half portion of the active layer, lower-half portion of the active layer, permafrost, and thermokarst lake sediment. The different soil samples were incubated in-situ in shaded conditions, in one of the shallow tundra ponds. These incubations were repeated under controlled conditions in laboratory (stable temperature and in darkness). During the incubations, dissolved oxygen (O2) and headspace CH4 and CO2 concentrations were measured regularly over 10 days, allowing calculation of the rates of consumption or production of the gases as a proxy for carbon lability. These experiments will be repeated in 2015 with a larger coverage of the different carbon pools. Also a larger set of bioindicators will be used to further qualify carbon lability and better understand the trends obtained this year.
Bouchard, F., Laurion, I., Preskienis, V., Fortier, D., Xu, X., Whiticar, M.J., 2015. Modern to millennium-old greenhouse gases emitted from ponds and lakes of the Eastern Canadian Arctic (Bylot Island, Nunavut). Biogeosciences, 12(23): 7279–7298. DOI: 10.5194/bg-12-7279-2015.