This thesis is organized in “sandwich” format, as recommended by my supervisory committee. It consists of three main chapters. Chapter one is a general introduction and outlines the background information leading to the objectives and hypotheses of my thesis research. Chapter two is a manuscript prepared for submission to a peer-reviewed scientific journal. Chapter three is an overview of the major findings of this thesis, their implications in fish physiology and ecotoxicology, including suggestions of future directions of research. Appendix A contains data from an additional series of experiments that were conducted during my thesis but are not included as a full data chapter. It will be prepared for publication after my defence. / Hypoxia often occurs in aquatic ecosystems that receive effluent from municipal wastewater treatment plants (WWTP). WWTP effluent contains contaminants that could disrupt the complex physiological pathways fish use to cope with hypoxia (e.g., pharmaceuticals, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons), but the effects of WWTP effluent on the physiological responses of fish to chronic hypoxia is poorly understood. We exposed mummichog killifish (Fundulus heteroclitus) to hypoxia (5 and 2 kPa O2) and/or WWTP effluent for 21 days in a full factorial design. We then measured hypoxia tolerance, whole-animal metabolism, gill morphology, haematology, and tissue metabolites. In clean water, killifish responded to chronic hypoxia with improvements in hypoxia tolerance – increases in time to loss of equilibrium at 0.5 kPa (tLOE) and decreases in critical O2 tension (Pcrit) – in association with increased gill surface area as a result of regression of the interlamellar cell mass (ILCM). Concurrent exposure to wastewater attenuated the increases in tLOE and gill remodeling in chronic hypoxia, and nearly depleted brain glycogen stores. Therefore, exposure to WWTP effluent can disrupt the physiological mechanisms fish use to cope with chronic hypoxia and impair hypoxia tolerance. My research suggests that the combination of stressors near WWTPs can have interactive effects on the physiology and health of fish. / Thesis / Master of Science (MSc) / Low oxygen conditions, known as ‘hypoxia’, frequently occur in aquatic ecosystems that receive municipal wastewater treatment plant (WWTP) effluent. WWTP effluent is a continuous and complex source of pollution, including contaminants that can disrupt fish physiology, affecting their ability to cope with stressors, like hypoxia. The effects of WWTP effluent on the responses of fish to chronic hypoxia are poorly understood. To address this research gap, I examined the effects of hypoxia and WWTP effluent on chronically exposed mummichog killifish. I provide evidence that combined exposure to hypoxia and wastewater affected hypoxia tolerance, gill structure, and depleted energy stores in the brain. My thesis demonstrates that WWTP effluent can disrupt mechanisms that fish use to cope with chronic hypoxia and impair hypoxia tolerance. These findings contribute to the existing body of work that documents the interactive effects of combined stressors in effluent-dominated ecosystems on the physiology and health of fish.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25864 |
| Date | January 2020 |
| Creators | Lau, Samantha Chi-Lok |
| Contributors | Scott, Graham, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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