NWT RESEARCH DATABASE

Regions: North Slave Region

Tags: physical sciences, water chemistry, permafrost thaw, carbon cycling

Objective(s): To determine the influence of permafrost thaw on the mobilization of carbon to stream ecosystems, and its subsequent effects on in-stream microbial communities and carbon cycling.

Project Description: This licence has been issued for the scientific research application No.4929. The objectives of this study are to determine the influence of permafrost thaw on the mobilization of carbon to stream ecosystems, and its subsequent effects on in-stream microbial communities and carbon cycling. The research team will measure stream water chemistry and collect water samples for microbial analysis at a series of sites where icings tend to form every year, and the lakes that source them. Icings accumulate during winter and can be sourced by water flowing from lakes, springs, or groundwater sources. Taliks are bodies of perennially unfrozen ground that reflect the thawing of near-surface permafrost; groundwater may flow through taliks during icing formation. Comparing icing and source water chemistry allows us to detect a “talik-signature” if permafrost thaw is occurring. Analyzing microbial community structure and biological processing in these samples will determine if thaw is influencing in-stream carbon cycling. Within the bounding mapped boundaries the research team will choose 1-2 icings for the focus of the study. Because icings do not occur at the same sites every year (or reliably each year within sites), specific sites within our focal area will be chosen after an initial scoping effort. The team will focus on sites where icings occur in association with stream water flow, so to allow sampling of icings (where frozen water is derived from talik flow) during the winter, and associated stream-water flow in the spring, summer and fall. For all chosen sites, the team will collect stream water samples using 1-2 litre bottles that will be submerged just below the water surface and filled. During winter, the team will collect samples from icings at 3-5 spots at each site using an auger. Water samples will be filtered at private accommodations using a simple vacuum pump. Further analyses will be conducted at the Taiga Lab in Yellowknife, and at the University of Alberta. For the stream water sampling, the team will not be collecting any biological specimens other than bacteria that occur naturally in filtered water samples. Most sampling sites can be accessed via roadside access, snowmobile or canoe except Moss Creek, which may have to be accessed via helicopter during the ice breakup period. At each site, the team may also collect soil samples at discrete locations. These samples will be collected using a narrow (< 10 cm diameter) soil corer. To measure pH, conductivity, dissolved oxygen and temperature, we will deploy a probe into the stream channel that will be removed after measurements are recorded. Sampling frequency will be weekly from mid-April to mid-May, and switch to biweekly for the rest of May. Summer sampling (June-August) will be monthly, and late winter sampling will consist of 1-2 sampling dates in late November to early December. The research team have specified a more general time frame in to allow for seasonal flexibility. Scientists from the Aurora Research Institute (Yellowknife) and NWT Geosciences Office have been central to the development of the proposed research plan. The research team will work with these scientists to ensure that the research plans and findings are disseminated to interested parties in the Yellowknife area. The research team are also more than happy to give school or public presentations while in Yellowknife. The fieldwork for this study will be conducted from April 10, 2021 to December 31, 2021.