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étiquettes: physical sciences, water quality, zooplankton, hydrology, aquatic food web, paleohydrology, biogeochemical processes, ice jams, environmental sensitivity index, thermokarst, delta floodplain, wildlife habitat

Description du projet: The long-term goal of this project is to develop a biogeochemical model for lakes in the Mackenzie Delta, and ultimately, a more general ecosystem model for floodplains and deltas of major world rivers that will help assess the effects of multiple stresses on rivers resulting from global change. Numerous major river deltas in the Arctic circumpolar region are lake-rich because of thermokarst effects. These complex systems may collectively represent several hundred thousand lakes that function as critical aquatic habitat for fish, birds, and mammals. They are sensitive to global change because thermokarst and jamming of river ice are highly temperature-dependent, and because deltas are affected by processes occurring throughout the drainage basin. Fieldwork will include collecting samples of water, algae, aquatic plants and zooplankton periodically over the summer from a set of six lakes located to the west of Inuvik and the East Channel. Additional water samples will be taken by helicopter from a set of forty lakes located to the west of Inuvik and the East Channel, and from a set of eight lakes located to the north of Inuvik along the East Channel. Laboratory analysis of these samples will be conducted at the Aurora Research Institute to determine organic matter composition and water optical properties, and to calibrate water colour against satellite images of the Mackenzie Delta. This technique will enable the tracking of how DOC in delta lakes may have historically changed over the past decades, and also allow for the prediction of future change based on the observation that spring break-up occurs earlier nowadays than in the past. With climatic warming, water levels in the Mackenzie River are expected to decrease because of reduced ice jamming in the river channels during break-up. Such a change in flooding regime will significantly alter DOC in delta lakes and the fuel available for aquatic bacteria. To observe bacteria growth in such circumstances, small experimental enclosures of lake water will be set up in one lake well-connected to the river and in one lake well-isolated from the river. Both sets of enclosures will allow the growth of aquatic bacteria communities to be tracked for short periods (approximately two weeks) in the presence and absence of grazing zooplankton. The two lakes for this experiment will be selected from the six lakes regularly monitored as part of this project. This information is necessary in understanding the relative role of bacteria (fuelled by DOC) versus photosynthetic organisms and their importance in ultimately supporting fish and aquatic birds. The study will be conducted from June 2 to September 15, 2006 within two clusters of lakes lying to the west of Inuvik and the East Channel, and to the north of Inuvik along the East Channel.