NWT RESEARCH DATABASE

Regions: South Slave Region

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

Objective(s): To determine the current status of nutrients and contaminants in Slave River Delta (SRD) wetland ecosystems; how trace elements (e.g., mercury) move through SRD wetland food webs; and, how water sources affect the availability of nutrients and trace metals in SRD wetlands.

Project Description: TThis licence has been issued for the scientific research application No.4841. The objective is to determine the current status of nutrients and contaminants in Slave River Delta (SRD) wetland ecosystems; how trace elements (e.g., mercury) move through SRD wetland food webs; and, how water sources affect the availability of nutrients and trace metals in SRD wetlands. The characterization of existing levels of trace metals in surface-runoff dominated SRD wetlands will provide insight into contaminant status of systems influenced by local runoff (supplied by local parent materials and long-range atmospheric deposition) versus flood-water dominated systems. Should trace metal enrichment be found in surface-runoff wetlands, this finding could inform future investigation of potential regional contaminant sources (e.g., Giant Mine). This study will focus on representative waterbodies from the wetlands of the SRD. 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). Years 1 and 2 of this program will focus on sampling and subsequent analysis of wetland media. 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). Year 1 will focus on field sites accessible by boat or foot, choosing among sites in the flood-prone, active region and sampling for runoff-dominated sites (accessible from the Jean River). Helicopter support will be sought from the Polar Continental Shelf Program in Year 2 to sample additional remote locations. This will bring the project total to at least five sites for each wetland type. Year 3 will focus on analyzing and integrating data from years 1 and 2 and completing project final outputs (peer-reviewed manuscripts, final report). If we receive air support in Year 2, a subset of Year 1 sites will also be sampled in Year 2 to assess inter-annual variability. If no air support is available in Year 2, two additional sites will be accessed by boat and foot for each wetland type with a subset of Year 1 sites repeated to assess inter-annual variability. Where possible, wetlands will be accessed and sampled by boat and along the shoreline. A small canoe or belly boat will be used for sampling deeper waters in those wetlands inaccessible by powerboat and too deep to safely wade. 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). All methods will be consistent with previous SWEEP protocols (Slave River and Delta research) and ENR protocols. 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. Additional funds will be applied for from the Northern Contaminants Program to analyse all archive materials from years 1 and 2 (sediment, periphyton, phytoplankton, zooplankton, benthic inverts and fish tissue). Water samples are the exception. These will be analysed for trace metals at the end of each field season. Measurements 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 P, soluble reactive P) and dissolved organic carbon. 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. Handling, transport and storage methods will be consistent with previous Slave River sediment investigations; Sediment will be analysed for total organic carbon content, particle size distribution, total phosphorus and P geochemistry, and 24 trace metals. Periphyton growing on the deployed samplers will be scraped from the glass plates into wide-mouthed sample bottles. Samples will be immediately put on ice for later freezing, transport, and freeze-drying. 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. 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. 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. All sample 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: 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, Sediment total phosphorus and phosphorus speciation will be performed using sequential extraction. 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. Due to Covid-19 restrictions, there will be no in-person report of project results to the community of Fort Resolution. Instead, video conferencing will occur with those groups wishing to do so. 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 followed by a financial report in June, 2020. 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 September 12, 2020 to October 31, 2020.