Permafrost thaw slumps, sediment dynamics and ecosystem health of upland tundra lakes within the western Canadian Arctic

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area

Tags: greenhouse gases, sediment, methylmercury, permafrost thaw, ecosystem, erosion, thaw slump, tundra

Principal Investigator: Droppo, Ian (1)
Licence Number: 16739
Organization: Environment and Climate Change Canada
Licensed Year(s): 2020
Issued: Aug 13, 2020
Project Team: Ian Droppo, Peter di Cenzo, Erika Hille, Tom Reid, Renee McFadyen, Edwin Amos, Christopher Weisener

Objective(s): To assess the permafrost thaw slump erosion and transport of its sediment by rainfall/runoff to depositional zones within Arctic tundra lakes.

Project Description: This licence has been issued for the scientific research application No.4759.

The overall objective of this research is to assess the permafrost thaw slump erosion and transport of its sediment by rainfall/runoff to depositional zones within Arctic tundra lakes. To achieve this, we will link a rainfall simulator with an annular flume (to simulate lake currents) located in the Hydro-ecology Monitoring and Research Facility (HMReF) located at Environment and Climate Change Canada (ECCC), Burlington, ON, to investigate the sediment processes (erosion from the landscape, transport to the lake, deposition within the lake), and to assess the fate and possible effects of such long-term sediment movement on the ecological health of lakes.

The specific objectives are to: 1) quantify the sediment characteristics (sediment particle size, rates of erosion, transport, deposition) within runoff from slump scars on the landscape (runoff generated by rainfall simulation), 2) assess the sediment dynamics (transport and deposition) within a simulated aquatic environment (using an annular flume), 3) assess the implications of this on lake ecology relative to ongoing climate change, and 4) using novel DNA technologies, microbial (e.g. bacteria) communities will be assessed with regards to the production of greenhouse gasses (GHGs) and those responsible for the conversion of inorganic mercury into bioavailable methylmercury (MeHg).

Fieldwork will be conducted on two paired (affected/unaffected by thaw slumping) upland tundra lake systems (Lakes 5A/5B; Lakes 4A/4B) draining into Noell Lake, located about 20 km NNE of Inuvik, NT. Fieldwork will involve sediment and water collections from these study lakes, as well as non-intrusive core water quality monitoring using water quality instrumentation (e.g., YSI water quality sonde).

Bulk thaw slump sediment samples will be collected from each of the slumps on the two affected lakes (120L per slump x 2 slumps) using stainless steel shovels and specially prepared sample containers. Lake bed sediment samples will be collected using a Ponar type sampler and/or a gravity corer. A total of approximately six lake bed samples will be collected from each lake. Each lake bed core will contain up to about 4L sediment – which translates to about 24L of lake bed sediment per lake (4 lakes). Sediment samples from the landscape (about 1L of sediment) will be collected at each of the 4 study sites using stainless steel shovels and specially prepared sample bags. Small sediment samples (surface sediment from the lake beds, from the slumps, and from the landscape) for the microbial work (e.g. bacteria) will be collected in very small sample vials (5 mL), frozen, and shipped in specialized containers to keep the samples frozen. About 3-5 vials will be collected from each sampling location, with each lake having about 10-20 sampling locations, each thaw slump having about 5-10 sampling locations, and 2-5 locations from the landscape in each lake catchment. This equates up to 500 mL of sediment from each lake bed (4 lakes), up to about 250 mL for each thaw slump (2 slumps), and up to about 75 mL for each landscape location (2 landscape locations). Sediment suspended in the lake water will be sampled using a continuous flow centrifuge system (MAB 103B Alfa-Laval Separator) equipped with stainless steel centrifuge bowls. Lake water is pumped to the centrifuges at 4 L per min using a submersible pump. The centrifuges are powered by one gas operated Honda 3000 generator. The centrifuge system is run until approximately 150g of suspended sediment has been collected from each lake (4 lakes). From the 150g of sediment collected in the centrifuge bowl, 3-5 small vials (5 mL) will be subsampled for microbial work, as described above. All sediment samples collected will be shipped to the Hydroecology Monitoring and Research Facility located at ECCC, Burlington, for laboratory analyses and experiments.

Lake water quality samples will be collected using a Van Dorn type sampler. About 20-30 L of water will be collected from each study lake. Should there be water flowing from a thaw slump, or if there is ponded water within a slump scar, up to 2L of water from the slump will also be collected. The water grab samples will be shipped to ECCC laboratories in Burlington and Saskatoon for water quality analysis.Detailed lake water quality profiles will also be obtained using water quality instrumentation (YSI 6600V2 or EXO2 water quality sonde on a cable).

At the Hydroecology Monitoring and Research Facility (HMReF), rainfall simulation on thaw slump sediment will provide a time-series of physical, geochemical and biological washoff characteristics. Using collected washoff from the rainfall/runoff experiments, fish toxicology will be undertaken in the Aquatic Life Research Facility (ALRF) at ECCC, Burlington, and sediment toxicology (using insect larvae that live in the lake bed sediment) will take place in the Sediment Toxicity Laboratory, ECCC, Burlington.

Investigations on the microbial community and function will be undertaken at the University of Windsor using high-throughput sequencing platforms for both DNA and RNA isolates, followed by advanced and novel microbial analyses (metatranscriptomics). Following the rainfall/runoff simulation, collected washoff will be transferred immediately into a 2m annular flume to simulate its transport dynamics (erosion, transport and fate). The flume is instrumented for real-time measurement of biogeochemical change during transport, including the immediate change and assessment of inorganic mercury compounds and methylmercury (MeHg). The same chemical/nutrient concentration measurements and biological indicators used for the washoff experiments will also be used for the linked flume/transport experiments.

To communicate results to individuals and communities in the North, the researchers will hold annual community-based meetings and consultations in northern communities to inform local residents in the region of the nature and significance of the research, what the research team are trying to find out and why, and to provide updates on what the team have learned (key findings) as the work progresses. Information will also be made available through such things as posters, brochures, fact sheets, journal publications, etc.

The research team will also visit the schools to reach out to the youth - the team plan to hold outreach events with students which will involve instruction on the use of field equipment and instrumentation, both in the classroom and with hands-on experience using the equipment/instruments out in a field setting.

Through consultations with Hunters and Trappers Committees, community members and community organizations, the team will share the respective environmental knowledge - local traditional environmental knowledge gained contributes to the planning of field activities.

The fieldwork for this study will be conducted from August 13, 2020 to December 31, 2020.