NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region

Tags: physical sciences, climate change, limnology, permafrost degradation, sedimentology, slumping

Objective(s): The objective of the Lake 5A mesocosm study is to better understand the impact of permafrost thaw shoreline slumping (an analogue for a warming climate) on the bottom components of the aquatic food-web in small Arctic tundra lakes in order to better predict the effects of a warming climate on food-web structure, function and productivity.

Project Description: The overall objective of the Lake 5A mesocosm study is to better understand the impact of permafrost thaw shoreline slumping (an analogue for a warming climate) on the bottom components of the aquatic food-web in small Arctic tundra lakes in order to better predict the effects of a warming climate on food-web structure, function and productivity. To assess the direct and indirect effects of permafrost thaw shoreline slumping on water column and lake bottom geochemistry, and related water column and lake bottom food-web responses, 12 small temporary mesocosm enclosures will be placed in Lake 5A near Inuvik. These enclosures are “box-like”, and are constructed using regular spruce 2x2s to make a frame (1.3 x 1.3 meters). Plastic sheeting is used to create walls around the enclosure leaving the top and bottom open. The enclosures are placed into the lake near the shore (in water about 1 meter deep) so that the bottom is open to the lake bed (to allow exchange between the sediments and the water in the enclosure), and with the plastic walls preventing the water inside the enclosure mixing with the lake water outside the enclosure. The installation of the small enclosures will occur in June (after the lake ice has totally disappeared) and a small (3-4 persons) temporary field camp (2-4 days) will be established during installation (June 8-11). Once the 12 enclosures are installed in the lake, 3 of them will be left as "control" enclosures (no slumped material added). The remaining 9 enclosures will be “treated” with three different levels of sediment (3 levels of sediment; 3 enclosures for each treatment level as replicates) from permafrost slumped material to investigate the effects of the slumped material on the bottom components of the food-web. This will allow us to compare the effects of the 3 levels of treatment on the food-web with the food-web unaffected by slumped material (in the control enclosures). Sediment for the purpose of the experiment will be retrieved from the permafrost thaw slump on nearby Lake 5B. The sediment from the Lake 5B permafrost slump will be placed into 5 gallon pails and transported by helicopter to Lake 5A. Each of the three treatment levels will consist of enough sediment to cover the bottom of enclosures to a thickness of 1, 2 and 4 cm – resulting in a volume of 17, 34 and 68 L of permafrost thaw slump sediment added, respectively. The enclosures will be treated once at the beginning of the experiment (June 14). All added, the experiment will only displace 350 L of sediment, which given the size of Lake 5A, is unlikely to have any effect on water quality after the enclosures are removed at the end of the field season. To quantify and qualify benthic macro-invertebrates (insect larvae living in lake bed sediments), three 10x10 cm cores to a depth of 5 cm will be removed from each enclosure at the beginning of the experiment, and another three at the end of the field season before the enclosures are removed. Cores will be brought back to the laboratory at Aurora Research Institute (ARI) and processed there. The experiment will last 12 weeks in total, with field visits every week or so (we plan to sample every Monday, but the actual day will depend on weather and environmental conditions), to sample water and sediment chemistry and associated pelagic (within water column) food-web (zooplankton/phytoplankton) dynamics. Water samples of 1-2 L will be taken from each enclosure on each sampling visit. To measure benthic (lake bottom) primary productivity, micro-cores (1cm in diameter; 1-2cm in length) will also be taken during each sampling visit. The samples obtained as part of this study will analysed in detail using specialized equipment in laboratories at Aurora Research Institute and/or University of Victoria. All enclosures will be totally removed from the lake at the end of the 2010 field season (September 13-14). Through consultations with HTCs, community members and community organizations, we will share our respective environmental knowledge - local traditional environmental knowledge gained will undoubtedly contribute to our planning of field activities. Aurora Research Institute (Inuvik) is a partner institution - ARI personnel provides us great assistance with logistics, field work, and laboratory analyses. Northern students and community members to assist in the field program will be identified through the Inuvialuit Joint Secretariat and the Aurora Research Institute. These individuals will be trained and hired to assist us with the field work and laboratory analyses. Wildlife Monitors will be utilized when necessary. To communicate results to individuals and communities in the North, we plan to hold community-based meetings and consultations in northern communities to inform local residents in the region of the nature and significance of the research, what we are trying to find out and why, and to provide updates on what we have learned (key findings) as the work progresses. We will also visit the schools to reach out to the youth. Information will also be made available through a project website, posters, brochures, fact sheets, etc. The fieldwork for this study will be conducted from June 8, 2010 to September 14, 2010.