The biogeochemistry and ecology of Arctic aquatic ecosystems

点击翻译按钮获取中文摘要

Permafrost, which covers about half of Canada's landmass, is thawing throughout the Arctic. One of the results of this change to our northern landscapes is that the carbon (C), and other constituents currently 'locked away' (sequestered) in frozen ground are becoming available for reaction within and liberation from soils, and transport to aquatic environments. We are proposing to work in the western Canadian Arctic to investigate changes in the delivery of dissolved inorganic and dissolved organic C (DIC, DOC) from land to the aquatic environment with permafrost thaw, and the implications of this change. Both DIC and DOC are central components of the overall C cycle, but with contrasting effect. On the one hand, DIC typically represents an atmospheric CO2 sink: bicarbonate (HCO3-), generally the largest component of the aquatic DIC pool, is mainly produced by chemical weathering, whereby CO2 dissolved in water (carbonic acid) drives chemical reactions with rock or mineral soils, and causes the original CO2 to become 'fixed' as HCO3-. In contrast, the DOC that is mobilized from permafrost soils by the dissolution of soil organic C in water represents a future CO2 source, following DOC degradation to CO2 by sunlight or bacteria. These processes are significant: while weathering is one of the two primary CO2 sequestration mechanisms on land, about twice as much organic C is sequestered by permafrost as currently exists in the atmosphere as CO2. This research will quantify changes in chemical weathering with permafrost thaw, the susceptibility of permafrost DOC to capture by mineral soils and degradation by sunlight and bacteria, and how the C balance of DIC creation and DOC liberation offset each other. As such, it will aid in our understanding of the future trajectory of the northern aquatic C cycle, focusing specifically on a region (the western Canadian Arctic) where warming is intense and permafrost thaw is causing massive thaw slumps. This work will result in the training of numerous highly qualified personnel. It will also specifically integrate northern training and northern knowledge into the research endeavour, and facilitate outreach to northern communities to enable northern input to, and feedback on, this work.