NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area

Tags: water quality, hydrology, carbon dioxide, methane, nutrient levels

Objective(s): To improve the understanding of methane cycling in Mackenzie Delta lakes and how it is affected by the changing water levels and to decipher the impact of water level changes on the ability of the Mackenzie Delta to affect riverine carbon and nutrient flow to the ocean.

Project Description: This licence has been issued for the scientific research application No.5554. The objectives of this project are to improve the understanding of methane cycling in Mackenzie Delta lakes and how it is affected by the changing water levels and to decipher the impact of water level changes on the ability of the Mackenzie Delta to affect riverine carbon and nutrient flow to the ocean. Improve understanding of methane cycling in Mackenzie Delta lakes: This work will help resolve what drives microbial communities in Mackenzie Delta lakes to either release the methane in these waters to the atmosphere or to convert the methane to a form consumed by fish and other organisms. Field work over the 5 years of the research licence (2022-2026) will be centered on an area of 40 lakes to the east of Inuvik where the research team have worked extensively in the past, but field work during 2022 will be limited to only a few of the lakes. Fieldwork quantified the importance of methane oxidation for limiting escape of methane from lakewaters to the atmosphere during open-water and that carbon-quality in the lakewaters is strongly related to methane production in under-ice lakewaters. Fieldwork documented the compositions of methane-producing versus methane-consuming microbes in lakewaters and surface sediments of the lakes. Fieldwork documented how methane oxidation rates limit escape of methane from lake sediments to overlying waters among Delta lakes. Results from each of the above have been published in several Maters of Science thesis and journal articles. During summer 2022, the team will follow up on key information gaps addressed by the following specific objective. Assessing how water-column mixing during under-ice and open-water conditions affects accumulation and evasion of water-column Methane (CH4) among Delta lakes: This will be done by high-frequency tracking of vertical profiles of water temperature, dissolved salts, dissolved oxygen, and under-water light through the period of winter ice cover, and through open-water paired with wind speed measurements. The team will learn about water-column mixing rates from the above measures, and learn how these results may account for water-column changes in methane tracked during our prior work. MSc student Lucy Burns may do some initial analyses of microbial community composition in the lakes to supplement Harrison's measurements. All fieldwork will be based from the Aurora Research Institute in Inuvik. The study lakes will be accessed from Inuvik by boat. During summer 2022, the fieldwork will be limited to a short (2 week) period during August, where a series of small under-water data loggers (recording temperature, salts, dissolved oxygen) will be deployed and left in place for the winter. These data loggers will simply be attached along a single under-water line (rope) and held with a small weight (25 lbs) on the lake bottom, and with the upper end of the line attached to a float positioned about 1 m below the lake surface. During summer 2023, methane emissions will be measured weekly during open-water (from June through August), and will be compared with results from the data loggers when they are retrieved at end of summer. To interpret the lake-water mixing and methane results, lake-water samples will also be collected for measurements of dissolved gases, dissolved organic-carbon content, and underwater light transparency. To understand how results from the selected lakes fits within the greater delta, samples of dissolved methane and lake-water also need to be collected from a larger set of 40 lake just prior to ice-out and once during open-water. These samples can be collected by helicopter and the flying can usually be completed in one day. Anticipated Changes in Methodology in Future Years: The research team expect the first three years of work (2022-2024) will focus on improving the understanding of methane cycling, with the locations being the same as during 2022, and the methods to assess the water-column mixing being very similar. During 2023 the team expect to quantify how methane producing microbes in the water-columns versus methane oxidizing microbes affect the methane content among the Delta lakes (MSc project of Lucy Burns). During 2025, the team expect to shift focus towards deciphering the impact water changes, which will involve doing less field work and more analysis of obtained results. The team do not expect the general methodological approach to change substantially in future years of this 5-year project. Potential changes will depend on results from prior years and whether new graduate students are brought into the project, but the team expect potential changes to be relatively minor. Most field work will still involve measuring dissolved gases and water quality of various forms. The team do not, for example, expect to switch from boating-based work on the waters of the Mackenzie Delta, to working directly on the land. The research team generally make an effort to publish the results of the work in top-ranked scholarly journals that are subscribed to by the library at the Aurora Research Institute. To make results more accessible to communities in the NWT, the PI have created and maintain websites on the long-term Mackenzie Delta research (http://www.sfu.ca/limnology) and the past International Polar Year research (IPY-SCARF) (http://www.sfu.ca/ipy). This promotes the research and highlights student opportunities for training in Arctic-based research. Students have given presentations at ARI Research Forums. The PI have given interviews via newspaper (Globe and Mail, Associated Press, Vancouver Sun, Edmonton Journal, News/North), radio (CBC North, Ends of the Earth), TV (CBC Northbeat), and Web-video (Rosenberg International Forum on Water Management in the Mackenzie River Basin). The PI is also happy to give a presentation or meet with anyone that might be interested in hearing about the work. The fieldwork for this study will be conducted from: May 8, 2023 to August 25, 2023.