Beneath the Surface: sub-lethal effects of parasites and pollutants on mammal energetics and implications for aquatic ecosystems.
Creators: Shanebeck, Kyle M
Publisher: name: University of Alberta Library
Year: 2023

<p>Sub-lethal infections by helminth parasites are generally considered unimportant for wildlife fitness. However, data on the sub-lethal effects of parasites, combined with the effects of anthropogenic stressors, are often lacking. To fill this gap in knowledge, I carried out a meta-analysis of the literature to determine if sub-lethal infections of helminth parasites significantly influence mammal energetic condition. In parallel, I surveyed the parasites and metal contaminants of the North American river otter (Lontra canadensis) and mink (Neogale vison) in Alberta and British Columbia, modeling their effects on host energetic condition. Parasite communities and metal contaminants were also compared against previous reports on otter and mink across North America collected via a systemic search of the literature.  Although river otter and mink are ecologically, economically, and charismatically important semi-aquatic mammals in Canada, little is known about their parasites and contaminants. As carnivores at the top of freshwater food chains, they are ideal sentinels of ecosystem health. Results of the meta-analysis showed strong negative effects of infection on mammal energetic condition across major taxa. Effect size was influenced by methodological bias, suggesting that research limitations may have driven assumptions of insignificance. Surveys of the parasite populations in sampled mink and otter showed a diversity of parasites, including multiple species of zoonotic concern, and was characterized by four main species (Alaria mustelae, Filaroides martis, Isthmiophora inermis, and Versteria rafei n. spp.). Most prevalent were infections by mesocercariae of A. mustelae (Trematoda:Diplostomidae), a zoonotic species, related to subacute to chronic inflammation, not previously reported in otter and mink in North America. Due to their economic importance as furbearing species, especially for First Nation and Metís peoples, otter and mink are a potential pathway for the spread of zoonotic pathogens. Concentrations of metal contaminants were generally high compared to historical reports in these species in North America; Silver, Cadmium, Copper, Iron, Gallium, Rubidium, and Strontium were present at particularly high concentrations. Gallium and Rubidium, which have historically received little attention, were seen at much higher levels than previously reported and may represent emergent contaminants of concern. Anthropogenic sources of contaminants are significant drivers of this trace metal contamination, especially industrial, mining, pulp and paper, and oil and gas activities, across both local and sub-watershed scales. Areas of concern where populations may be more at risk include coastal populations along the Salish Sea, including Vancouver Island and the Sunshine Coast, the Columbia and Thompson River valleys and other environments impacted by coal mining, transport, and processing, and watersheds within the Alberta oil sands. Energetic condition was significantly influenced by mesocercariae of A. mustelae and elevated levels of essential metal contaminants, especially Copper and Zinc, and by Gallium, a rarely studied non-essential metal contaminant. Overall, the findings of this study highlight serious gaps in knowledge concerning the importance of sub-lethal stressors such as parasites and metal contaminants in mammals. It synthesized the current state of the literature regarding sub-lethal effects of helminths on mammals and historical reports of metal contamination in otter in mink to create averages for easy comparison. As well as expanding our understanding of contaminant exposure and parasitic infection in aquatic mammals in Western Canada. This work suggests that parasites and contaminants are significant, interacting stressors on mink and otter populations. Future work on the potential effect of rising temperatures on parasite success, contaminant bioavailability, and their cumulative effects on mammal fitness is urgently needed.  </p>