Assessing the limnological effects of 20th-century silver mining, piscicide use, and recent climate warming in central Yukon, Canada

Jones EA, Would JA, Nesbitt LVR, Rear LA, Pisaric MFJ, Grooms C, Michelutti N, Smol JP. 2026. Assessing the limnological effects of 20th-century silver mining, piscicide use, and recent climate warming in central Yukon, Canada. Lake Reserv Manage. XXX–XXX.Paleolimnological techniques and modern water quality measurements were used to determine whether metal-laden dust generated by mining operations near Keno City (central Yukon) has been deposited into nearby lakes. These lakes are important freshwater resources located on the traditional territory of the First Nation of Na-Cho Nyäk Dun. Present-day water chemistry analyses from 8 of these lakes, situated 13.5 to ∼40 km from Keno City, do not suggest a clear pattern of metal enrichment caused by mining. Downcore metal analyses of sediment cores from 3 study sites (Hanson Lakes, McQuesten Lake, and Roop Lakes) showed no clear evidence of aerially transported dust following the onset of mining around the 1920s. Increases in sedimentary metal(loid)s recorded in the McQuesten and Roop sediment cores over the past ∼50 yr do not track the onset of large-scale mining near Keno City and are likely related to mining activities that occurred later within their respective catchments. A downcore assessment of biological indicators in Hanson Lakes, the site nearest Keno City (13.5 km), shows that cladocerans assemblages were likely restructured by the application of piscicides in 1963, whereas diatoms responded slightly later to climate-related changes in lake ice and mixing regimes after ca. 1960. Overall primary production also increased in response to both stressors. Collectively, our data suggest dust deposition from silver mining near Keno City minimally affected regional lakes and that climate and other stressors (piscicides, local placer mining) were larger drivers of aquatic ecological change.