Trophic structure and mercury transfer in the subarctic fish community of Great Slave Lake, Northwest Territories, Canada

• Main Authors: Chételat, John, Rohonczy, Jillian, Cott, Peter A., Benwell, Amanda, Forbes, Mark R., Robinson, Stacey A., Rosabal, Maikel R., Amyot, Marc
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2020
• Subjects: Mercury; Great lake; Burbot; Catostomus catostomus; Great Slave Lake; Longnose sucker; Lota lota; Northwest Territories; Subarctic; Yellowknife; lota
• Online Access: https://doi.org/10.5061/dryad.59zw3r23g

In recent decades, mercury concentrations have increased in fish of Great Slave Lake (GSL), a subarctic great lake in northern Canada with important recreational, subsistence, and commercial fisheries. This study characterized habitat use and trophic position of common fish species in GSL near the City of Yellowknife (Northwest Territories, Canada), measured mercury concentrations in water and in taxa from lower trophic levels of the food web, and examined trophic and biological influences on mercury concentrations within and among fish species. Northern pike ( Exos lucius ) and lake whitefish ( Coregonus clupeformis ) fed predominantly nearshore, cisco ( Coregonus artedi ) and longnose sucker ( Catostomus catostomus ) fed predominantly offshore, and burbot ( Lota lota ) fed roughly equally in both habitats. Habitat-specific feeding did not influence mercury bioaccumulation in fish, in contrast with published studies of smaller lakes. Water concentrations of total mercury and methylmercury were low and showed little spatial variation among sites or depths. Zooplankton (>200 µm) had similarly low methylmercury concentrations to littoral and profundal amphipods, suggesting little habitat-variation of mercury exposure near the base of the food web. Age, size, and trophic position were significant explanatory variables for muscle total mercury concentrations within populations of fish species. Among fish species, size and trophic position explained 80% of the variation in muscle total mercury concentrations. This study generated the most comprehensive dataset to date on mercury bioaccumulation in the food web of GSL, which will serve as a baseline for future studies of this great lake. Funding provided by: Environment Canada Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100000039 Funding provided by: Fisheries and Oceans Canada Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100000041 Funding provided by: Cumulative Impact Monitoring Program, Government of the Northwest Territories* ...