Base de données de recherche des TNO

étiquettes: physical sciences, water quality, aquatic ecosystems, climate change, permafrost degradation, slumping, environmental change, terrestrial ecosystem, tree growth

Objectif(s): To examine the impacts of climate and environmental change on freshwater ecosystems in the Inuvik region across a variety of spatial and temporal scales. Specifically, the researchers are examining the impacts of permafrost degradation and subsequent thaw slumping on freshwater ecosystems and the impact of climate change on tree growth in the Mackenzie Delta.

Description du projet: This licence is being issued for the scientific research application No.1005. Climate change and industrial contaminants are two principal concerns for Arctic residents. The objectives of this research are to examine the impacts of climate and environmental change on freshwater ecosystems in the Inuvik region across a variety of spatial and temporal scales. Specifically, the researchers are examining the impacts of permafrost degradation and subsequent thaw slumping on freshwater ecosystems and the impact of climate change on tree growth in the Mackenzie Delta. Lake sediment sampling The lake sediment sampling will occur during the late winter/early spring season and during mid-summer in 2009. The late winter/early spring field work will occur while the lakes are still ice covered. The researchers will target 4 lakes to recover long sediment records spanning most of the Holocene. Using the ice cover as the coring platform, the researchers will use a Livingstone piston corer to recover longer sediment profiles from these lakes. The piston coring system allows them to collect several metres of sediment from lakes with depths varying from a few metres to 10-15 metres. They will use a gas powered ice auger to cut through the ice cover and will carry a spill clean up kit with them at all times. Joshua Thienpont will examine these cores for their sub-fossil diatom assemblages while Joshua Wixom will examine the records for their sub-fossil charcoal and pollen content. Jesse Vermaire will also examine these cores for their sub-fossil chironomid assemblages. In the summer of 2009 another 40 lakes in the study region will be visited to obtain the surface sediment from the bottom of each lake. The researchers will use an inflatable raft to paddle out to the centre of each lake to recover the surface sediments. A Glew gravity coring system will be used to obtain undisturbed sediment profiles from the lake bottom. None of the coring systems used in this study will cause any significant disturbance to the lake bottom sediments. These sediments will be examined for their sub-fossil chironomid and diatom assemblages to compare the modern communities from lakes with permafrost slumping to those that contain no active (or recently active) slumps. Lakes near abandoned drilling mud-sumps will also be targeted. The drilling mud-sumps contain materials such as potassium chloride which was added during the drilling process to depress the freezing point of the mud when drilling through the permafrost. Some of these abandoned drill sumps have failed and their contents are now making their way into nearby freshwater lakes and ponds. The researcher will also collect surface sediment from these lakes to determine if sub-fossil diatom and chironomid assemblages from contaminated lakes differ from nearby pristine systems. At each lake, water samples will be collected to analyze for water chemistry, including chloride concentrations. Longer sediment cores (top 30-40 cm of sediment) will also be collected from a subset of the ponds described above. These will be analysed for changes in chemistry related to contaminants such as chlorides which should provide estimates of the timing of recent drilling mud-sump failure. These sediments will also be analysed for their sub-fossil diatom and chironomid assemblages to investigate the impact of sump-failure on these ecosystems. Sampling for contaminants: Water sampling for persistent organic pollutants (POPs) will be done by passive samplers, consisting of a semi-permeable membrane containing a resin that will extract contaminants from water. This sampler is suspended on a line in the water column between a float and a small weight anchored to the lake bottom. This device is placed in shallow water to slowly sample any hydrophobic organic contaminants in the water column for a period of about 3 months. This passive sampler is totally unobtrusive, and has no environmental impact whatsoever. This research will be undertaken by Sarah Cebulski in association with Jules Blais. The researcher will suspend these passive water samplers in the water columns of 22 lakes, 11 that have experienced permafrost slumps in their catchment, and 11 that have not. Additional samplers will be deployed in 5 lakes where drilling mud-sumps are present in their catchments. Water samples will also be collected for later analysis of total nutrients, major cations and anions, dissolved organic carbon, pH, and other basic water quality variables. Food web sampling: The researchers propose that permafrost degradation will lead to higher organic and metallic contaminants in lakes that may in turn bioconcentrate and biomagnify in these aquatic food webs. To test this hypothesis, the researcher will select 4 lakes (2 affected by thawing permafrost, and 2 unaffected) and sample sediments, phytoplankton, periphyton, benthos, zooplankton, invertebrates, fish and mammals from the case-control lake design to determine if food webs affected by permafrost degradation accumulate higher contaminants. They will employ established techniques to identify trophic structure and trophic position in these food webs by identifying stomach contents and stable isotopes of nitrogen and carbon in tissues of the aquatic food web and describe food web biomagnification patterns by relating contaminant concentrations with trophic positions. Todd will lead this research in association with Jules Blais. Tree sampling: The final aspect of the research activities will focus on the examination of tree growth at two sites in the Inuvik region. One of the sites, Blueberry, has been sampled previously by this research team and a second site (Gwich'in Jak Park) may be established (pending sufficient funding and approval) this summer. Both sites will be operated in association with northern partners at the forestry division of GNWT. Trees at the Blueberry site will again be instrumented with automatic point dendrometers. These trees were previously instrumented in the summers of 2006 and 2007. The dendrometers consist of two small screws inserted into the trunk of the tree, a mechanical balance that rests against the trunk, and a data transfer wire that runs from the tree to a central data logger. A small (approx. 2 m diameter tripod) portable meteorological station will be set up at the Blueberry site to measure temperature, relative humidity, incoming solar radiation, and soil moisture at 30 min. intervals. The fieldwork at the spruce forest sites will largely be carried out in early May and then again in early September when the dendrometers will be removed from the trees for the winter season. Tree cores will also be collected from approximately 30 trees/site from white spruce stands on the uplands between Noell Lake and Eskimo Lakes. A small core (~4.3 mm in diameter) is removed from each tree. If dead snags or old logs are present on the ground, the researchers will cut a 1-inch thick cookie from these samples. In the case of dead standing snags, they will not disturb trees that appear to be nesting sites for any birds. It is anticipated that the team will visit approximately 5-10 sites during the research. The researchers anticipate hiring at least one individual from Inuvik to help with the field work proposed in this application. The individual will serve as a field assistant and wildlife monitor. The results of all components of this project will be communicated in a number of media including, but not limited to, written reports, scientific publications, oral presentations, and poster presentations. Copies of these communications will be made available to the Aurora Research Institute upon completion. This research will also form a significant component of the thesis research of a number of students. These theses will be submitted to the ARI once they have been accepted by the respective School of Graduate Studies. The fieldwork for this study will be conducted around the central and western Mackenzie Delta, east of the Delta around Noell Lake and the Gwich’in Jak Park from May 8 to December 31, 2009.