Impacts of the Changing Global Environment at Nunavut?s Northern Frontier
Influence of thawing permafrost on aquatic food webs
The boreal forest and the subarctic tundra hold one of the Earth?s largest pools of organic carbon. Climate warming and associated changes in permafrost thawing and forest dynamics have increased the risk that this carbon becomes a source of greenhouse gasses. This scenario has drawn attention to carbon cycling in tundra ecosystems, including higher organisms like zooplankton that may be able to convert allochthonous carbon to somatic growth before it enters the atmosphere. In this thesis, the focus is on the growth rate of zooplankton populations, as well as the assimilation of different carbon sources by zooplankton, in a series of ponds undergoing different levels of thawing permafrost. More precisely, the overall objectives are to (1) study the zooplankton vertical distribution in thaw ponds and how it relates to the vertical gradient resources; (2) determine the role of landscape type on zooplankton net growth and diet, via differences in allochthonous dissolved organic carbon (DOC) export. Field studies will be carried out along a DOC gradient of < 0.5 ? > 50 mg C L-1. This gradient will span from boreal forest to shrub tundra, with sampling in the vicinity of the CEN research station at Whapmagoostui-Kuujjuarapik. The research methods will include measurements of crustacean molting enzyme chitobiase, as an indicator of the zooplankton growth rate, and identification of fatty acid-specific d13C food markers. These researches will contribute to a better understanding of arctic freshwater ecosystems, and will allow to predict the responses of zooplankton communities to climate change and their potential impact on the food chain.