Comparison of Mercury Dynamics in High Arctic Lakes

• Main Author: Hudelson, Karista Elizabeth
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Windsor 2020
• Subjects: Arctic; Cornwallis Island; Lake; Mercury; Salvelinus alpinus; Warming; Arctic Lake; Cornwallis; Island Lake; Climate change
• Online Access: https://scholar.uwindsor.ca/etd/8301; https://scholar.uwindsor.ca/context/etd/article/9306/viewcontent/uc.pdf

Arctic lakes and their watersheds are being simultaneously subjected to the deposition of atmospheric pollutants such as mercury (Hg), and warming. Once Hg enters an ecosystem, it may become methylated, greatly increasing its toxicity and reducing organisms’ ability to eliminate it. Mercury is bioaccumulative and thus found at high concentrations in land-locked Arctic char (Salvelinus alpinus) and other top predators. In sediment, Hg methylation rate is temperature-dependent, and [Hg] in Arctic predatory fish has been correlated with trends in air temperature. Despite reductions in Hg emissions in North America and Europe, [Hg] continues to rise in some Arctic species. The purpose of this study was to better understand how climate change may influence Hg flow through Arctic lake food webs. The effect of temperature differences on Hg methylation and dynamics were examined in laboratory-based temperature manipulation experiments and by studying natural variation in temperature between shallow and deep lakes. Additionally, time-series of [Hg] in Arctic char were characterized and relationships between these time-series and climate trends were examined. The sediments of the shallow, warmer lakes demonstrate higher Hg methylation potentials than those of the cooler, deeper lakes, but differences between lakes were small, possibly due to the ultraoligotrophic nature of the sediments. Additionally, the midge larvae (Diptera: Chironomidae; which represent the bulk of the invertebrate biomass and the bulk of Arctic char diet) and Arctic Char) of the two shallow lakes exhibited lower methyl-Hg (MeHg) bioaccumulation factors than larvae and Arctic Char of the two deep lakes . The results of the analysis of time-series of [Hg] trends in Arctic char indicate that differences between the shallow and deep lakes Arctic char populations were sustained over time. Considered together, these findings indicate that while Hg methylation and MeHg demethylation influence concentrations of MeHg in sediment, differences in the MeHg ...