Base de données de recherche des TNO

étiquettes: physical sciences, contaminants, 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; and to examine 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: 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 will occur during the late winter/early spring season and during mid-summer in 2011. The late winter/early spring field work (late April - early May) will occur while the lakes are still ice covered. Four lakes will be targeted to recover long sediment records spanning most of the Holocene. Using the ice cover as a coring platform a Livingstone piston corer will be used to recover longer sediment profiles from these lakes. The piston coring system allows for the collection of several metres of sediment from lakes with depths varying from a few metres to 10-15 metres. A gas powered ice auger will be used to cut through the ice and will carry a spill kit at all times. Sediment cores will be examined by a number of different students for a variety of fossils preserved within them. In the summer of 2011 another 15-20 lakes in the study region will be visited to obtain the surface sediment from the bottom of each lake. An inflatable raft will be used 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. Surface sediment samples will be collected 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 biological communities that may reflect contaminant inputs such as chlorides into the lakes. This could 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. In 2011, a number of lakes in the outer delta will be revisited which are referred to as the Dead Zone. This area is located to the southwest of the Kendall Island Bird Sanctuary and Richards Island. Using the same methods described above, a number of small lakes in the area will be visited to collect sediment from the bottom of the lakes. A Livingstone piston corer will be used to recover the sediment and a gravity corer to obtain the top, less cohesive sediment. 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 1 month. This passive sampler is totally unobtrusive, and has no environmental impact whatsoever. These passive water samplers will be suspended 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. Samplers will be deployed in early-June and will be retrieved in early July. 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. 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, four lakes will be selected (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. Established techniques will be employed 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. The final aspect of research activities will focus on the examination of tree growth at a site located on the Mackenzie Delta East Channel. This research is carried out in conjunction with northern partners at the forestry division of GNWT. Trees at the site will again be instrumented with automatic point dendrometers. These trees were previously instrumented in the summers of 2006, 2007 and 2010. 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 site to measure temperature, relative humidity, incoming solar radiation, and soil moisture at 30 min. intervals. 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 sites from white spruce stands on the uplands between Noel 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, a 1-inch thick cookie will be cut from these samples. In the case of dead standing snags that appear to be nesting sites for any birds, these stands will not be disturbed. The researchers anticipate visiting approximately 5-10 sites during the tenure of this research project. The researchers anticipate that there will be educational and economic benefits for the northern resident(s) hired as assistant(s). The assistant(s) will be trained in methodologies used in dendrochronological and paleoecological techniques. They will also gain experience in sampling biotic and abiotic components of the environment for contaminants that are potentially accumulating in the ecosystem. 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 from April 13, 2011 to December 31, 2011.