NWT RESEARCH DATABASE

Tags: physical sciences, contaminants, fish sampling, sediment, water chemistry, wetlands, nutrient levels

Objective(s): To provide insight into the sensitivity of Slave River Delta wetland habitat quality to changes in water source and contaminant status.

Project Description: Through this research the team will answer the following questions: 1. From the outer Slave River Delta (SRD) to the apex of the SRD, what is the current status of nutrients and contaminants in SRD wetland ecosystems? 2. How do trace elements (e.g., mercury) move through SRD wetland food webs? 3. How does water source affect the availability of nutrients and trace metals in SRD wetlands? Wetlands in the SRD are generally small and shallow (<4 m) and are recharged mainly by either river floodwater or snowmelt, depending upon the height of the levee separating them from the river. The research team will sample selected sites from flood-dominated (five sites total over two years) and surface-runoff dominated wetlands (five sites total over two years). Sampling will occur in the summer, with an initial reconnaissance and periphyton (algae and microbes growing on surfaces) sampler deployment, followed by retrieval of these samplers approximately four weeks later once mature biofilms have developed on each sampler. Each sampler will hold 3 frosted sheets of glass in an upright orientation. Periphyton sampler retrieval will be accompanied by sampling of water, sediment, phytoplankton, zooplankton, benthic invertebrates and small-bodied fish (where possible). Environmental compartments sampled from each waterbody will include materials from a minimum of three stations suitably spaced apart for independence of samples (e.g., minimum of 50 m). The scope of this work will be limited to tissue residue analysis for each environmental compartment. Given annual budget limitations, trace metals analysis will focus on mercury for the first year, with all samples archived for later trace metals analysis. Water samples will be analysed for trace metals at the end of each field season. Water measurements will be collected using a combination of field techniques and laboratory analyses on bottled samples. A minimum of three water samples will be collected for each analysis from each small waterbody. Additional samples will be collected from Ring Lake to characterize spatial trends within this lake. Variables measured will include temperature, turbidity, pH, hardness, alkalinity, conductivity, dissolved oxygen, trace metals content (dissolved), chlorophyll A, nutrients (nitrate, nitrite, ammonia, total phosphorus, soluble reactive phosphorus) and dissolved organic carbon. For sediment sampling the top 1-cm of surface sediment will be collected using a grab sampler or sediment corer. Three samples per station will be pooled and homogenised. Sediment will be analysed for total organic carbon content, particle size distribution, total phosphorus and geochemistry, and 24 trace metals. Periphyton growing on the deployed samplers will be scraped from the glass plates into wide-mouthed sample bottles. Benthic invertebrates (bottom-dwelling invertebrates) will be collected using a D-frame dip net. Samples for identification will be preserved onsite, while samples for tissue analysis will be bottled and immediately put on ice for later freezing, transport, and freeze-drying. Zooplankton and phytoplankton will be collected using vertical hauls of 64 µm and 200 µm mesh nets. Subsamples for taxonomic analyses (archived, additional funds required) will be preserved in formalin, and tissue samples will be immediately put on ice for later freezing, transport, and freeze-drying. Analysis will include 24 trace metals and stable isotopes of C, N and S. Where present, small-bodied fish (minnow species) will be collected using D-frame nets or a beach seine. Identification will be performed by the sampler. Tissue samples will be immediately put on ice for later freezing, transport, and freeze-drying. Tissue analysis will include 24 trace metals and stable isotopes of C, N and S. In addition to general water chemistry (including nutrients), the following analyses will be performed at the Toxicology Centre, University of Saskatchewan: a) Water, sediment and tissue samples (biofilm, algae, zooplankton, fish) will be digested and analysed for trace metals, total and methyl mercury. Samples for C, N and S stable isotope analysis will be sent to UC-Davis for analysis (fee-for-service); and, b) Sediment total phosphorus and phosphorus speciation will be performed using sequential extraction. This project will be conducted in partnership with Fort Resolution community members and will build upon capacities and relationships developed among participants since 2013. Specifically, the team is comprised of Dr. Lorne Doig (University of Saskatchewan), the Deninu Kue First Nation (represented by Kathleen Fordy, Aquatics Coordinator), the Fort Resolution Métis Council (represented by Shawn McKay, Environment Coordinator) and GNWT-ENR (represented by Chris Cunada, Coordinator, Aquatic Monitoring and Research). Field trip reports will be filed shortly after each outing with all participating organizations. These will be very visual to facilitate communication to community members and the layperson. Annual reports of all activities and findings will be provided to all participating organizations in January of each year, prior to organization of the next field season. In-person report (a co-presentation with named team members) of project results will be compiled and presented to the community of Fort Resolution. An annual report and budget will be submitted to Cumulative Impact Monitoring Program (CIMP) in February of each project year. A final report and budget will be submitted to CIMP in April, 2022. All metadata, project reports and peer-reviewed outputs will be made available to CIMP and the public by uploading the information to the NWT Discovery Portal and the Mackenzie Datastream. The fieldwork for this study will be conducted from July 8, 2019 to August 16, 2019.