Trapped river otters (Lontra canadensis) from central Saskatchewan exhibit differences in total and organic mercury concentrations with sex and geographic location

• Main Author: Wilkie, Steven Charles
• Other Authors: Hall, Britt, Somers, Christopher, Espie, Richard
• Format: Thesis
• Language: English
• Published: Faculty of Graduate Studies and Research, University of Regina 2016
• Subjects: Canada; Regina; Churchill River; Lontra
• Online Access: http://hdl.handle.net/10294/7714; http://ourspace.uregina.ca/bitstream/handle/10294/7714/Wilkie_Steven_200228813_MSC_BIOL_Spring2017.pdf

A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Science in Biology, University of Regina. ix, 71 p. Human activities have resulted in increasing amounts of mercury Hg(II) in the atmosphere, oceans, and terrestrial systems. Biological processes convert inorganic forms of mercury released into the atmosphere into the neurotoxic and bioaccumulating methylmercury (MeHg) species resulting in increased concern for Hg emissions entering the biosphere. Once deposited from the atmosphere, in-situ methylation of inorganic Hg in sediments is believed to be the largest source of MeHg to freshwater aquatic systems compared to input from the terrestrial environment (i.e. run-off) or atmospheric deposition. Methylation of Hg is predominantly a microbial mediated process that is facilitated by some sulfate and iron reducing bacteria, as well as methanogens. Biological activity, nutrient availability, pH, temperature, redox potential, and the presence of inorganic and organic complexing agents have significant effects on rates of methylation. Degradation of MeHg can occur as well, so that the amount of MeHg available to organisms is a result of two opposing processes. Mink (Mustela vison) and otter (Lontra canadensis) are the most studied mammalian wildlife species with regard to Hg exposure and toxicity. Data indicate that consumption of diets that contained Hg (as MeHg) >1 mg kg-1 wet weight can cause neurotoxicity and death in adult mink and otter. Neurological signs in MeHg-intoxicated mammals typically include lethargy, ataxia, limb paralysis, tremors, convulsions, and ultimately death. Here, I measured Hg concentrations in fur, liver and kidney tissues removed from river otters (Lontra canadensis) collected from trappers in central Saskatchewan (n = 203) over two trapping seasons. Total Hg (THg) concentrations measured in otter tissues were consistent with tissues measured in other non-impacted sites in Canada. Fur THg was positively correlated with total and organic Hg measured in liver and kidney tissue, highlighting the potential for using fur as a rapid and less expensive method of monitoring Hg in mammals. Livers from males had significantly higher mean organic Hg concentrations than livers of females (p = 0.015), however, no sex related differences were observed in kidney organic Hg concentrations. Total Hg concentrations in the fur of otters collected in the Churchill River Upland (Boreal Shield ecozone) was significantly higher (p < 0.001) than otters collected from all other ecoregions located in the Boreal Plain ecozone. Otters trapped in close proximity to the now decommissioned smelter located in Flin Flon, MB contained the highest concentrations of total Hg measured in my study. Student yes