NWT RESEARCH DATABASE

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

Objective(s): To understand microbial carbon-processing 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 nutrient flow to the ocean.

Project Description: The objective of this research project are to: 1) improve the understanding of microbial carbon-processing in Mackenzie Delta lakes and how it is affected by the changing water levels; and, 2) to decipher the impact of water level changes on the ability of the Mackenzie Delta to affect riverine nutrient flow to the ocean. This work will help resolve what drives microbial communities in Mackenzie Delta lakes to release the carbon in these waters to the atmosphere or to convert the carbon to a form consumed by fish and other organisms. Field work will be based on four areas within the delta, plus delta channels by the water gauging stations of Water Survey Canada, where the research team have worked extensively in the past. Quantifying how methane oxidation rates limit escape of methane from lake sediments to overlying waters will be done by tracking methane oxidation rates within the surface sediments of lakes in the study network throughout open-water. A key measurement is the growth in thickness of the oxidized sediment layer by late summer and how this varies among the lakes. All fieldwork will be based from the Aurora Research Institute in Inuvik. Weakly measurements of methane oxidation during open-water (from June through August) will be compared in 2 thermokarst lakes versus 2 macrophyte-rich lakes versus 2 high flood-frequency lakes. These lakes will be accessed from Inuvik by boat. To interpret the 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 above 6 lakes fits within the greater delta, samples of dissolved methane and lake-water also need to be collected in a larger set of lakes at 3 differing times from just after ice-out (early June) until late summer (latter August) conditions. Based on past experience, these samples can be collected from the helicopter floats and the flying can be completed in one day. Quantifying how carbon quality of lake sediments affects methane production among Delta lakes will be done by taking lake sediment cores at end-of-winter prior to ice-out in the study network of 40 lakes and measuring vertical profiles of carbon-quality in the sediments and pore-waters. Sediment c-quality will be assessed against methane results from 2014 and 2016. To interpret the sediment quality results, lake-water samples will also be collected for measurements of dissolved gases, and dissolved organic-carbon content. This requires landing on the lakes and augering through the ice for sample collection. Based on past experience with ice augering, this work can be done in a relatively short period by accessing these lakes by helicopter during early to mid-May. This project will advance the general understanding of how the lakes in the Mackenzie Delta will respond to global change stresses such as, climatic warming, sea-level rise, changes in Mackenzie River flow, and Arctic regional changes in ultraviolet radiation. The research team will publish the results of the work in top-ranked scholarly journals that are subscribed to by the library at the Aurora Research Institute (ARI). To make results more accessible to communities in the NWT, the Principal Investigator has created and maintains websites on the long-term Mackenzie Delta research www.sfu.ca/limnology and the past International Polar Year research (IPY-SCARF) www.sfu.ca/ipy. This promotes the research and highlights student opportunities for training in Arctic-based research. The research team have given presentations at ARI Research Forums. The team have also 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 research team are also happy to give presentations or meet with anyone that might be interested in hearing about the work. The fieldwork for this study will be conducted from May 1, 2017 to August 29, 2017.