Understanding and Predicting Mercury in Dehcho Lakes, Northwest Territories

Samples/data collected by joint University-community monitor team during on the land camps in 2018-2024. Data Collection: a. Fish (15-20 individuals/species, up to 4 food fish species/lake: captured with gill nets and dissected); Mercury concentration in fish flesh, stable isotopes of carbon and nitrogen in fish flesh, fish age. b. Benthic Invertebrates and sediments (min. 3 samples/taxa at 5 sites/lake); Profundal and littoral invertebrates collected with Ekman dredges and kick nets; Samples coarsely sorted in the field to Order, divided in half, and: i) preserved in ethanol for taxonomic identification; ii) frozen for stable isotope and total and methyl Hg analysis; Sediments collected with an Ekman dredge, frozen for analysis of Hg and MeHg. c. Zooplankton (min. 3 sample/size fraction at 3 sites/lake); Collected with vertical tows, size-fractioned in the field; Half of each size fraction preserved in ethanol for community composition analysis, other half frozen for stable isotope and total and methyl Hg analysis. d. Water (min. 3 sites/lake – top and bottom); Filtered and unfiltered water samples collected from each lake, and from influent streams and wetlands. Ultra-trace sampling methods used for mercury. e. Abiotic; Catchment size and slope, lake area and volume, % wetlands and hydrology in catchment, underlying geology determined using GIS. Laboratory Analysis: Standard water chemistry: University of Alberta (ions, nutrients, chlorophyll-a); Total and methyl mercury analyses: Western University (ISO-accredited); Stable isotope ratios of carbon and nitrogen: University of Waterloo; Fish age: AAE Tech (Manitoba).