Fish as indicators of ecosystem health: Assessing the impact of contaminants of emerging concern

Abstract

Water is arguably the most essential natural resource in the world, yet the use of industrial, healthcare, and household products threaten freshwater ecosystems. Contaminants of emerging concern (CECs) are a diverse group of chemicals - often defined as chemicals that were previously unknown, unrecognized, or unregulated - that comprise pharmaceuticals, personal care products, and hormones. CECs now have a ubiquitous distribution worldwide and their presence is only increasing as quantitative detection limits continue to be lowered and new chemicals make their way onto the global market. Concern over their biological effects at the molecular, organism, and population level in aquatic ecosystems is also increasing. CECs are identified throughout the Great Lakes Basin and may have a variety of adverse effects on aquatic life. However, data describing the specific risks these contaminants pose to human, wildlife, and environmental health are scarce. The goal of this thesis was to characterize CECs in freshwater ecosystems of northeastern Minnesota and evaluate their potential impact on the health of subsistence fish species. We investigated CECs and fish health within the Grand Portage Indian Reservation (GPIR) and 1854 Ceded Territory, where the Grand Portage Band of Lake Superior Chippewa rely on subsistence hunting, fishing and gather as the foundation for their culture and way of life. Thus, to establish a baseline understanding of CECs on these Tribal lands and their potential impact on fish health, we assessed important subsistence fish species in waterbodies that have value as fish harvesting locations for Band members. Further, due to a gap in knowledge regarding the distribution of CECs in rural and Tribal areas, we targeted waterbodies along a spectrum of anthropogenic pressures: waterbodies with no human development along their shorelines, those with development, and those directly impacted by wastewater effluent. Chapter 1 provides background for why it is essential that we better understand the potential impact CECs might be having on aquatic ecosystems, and thus Ojibwe culture. Chapter 2 characterizes the occurrence of CECs in water, sediment, and subsistence fish species in 28 locations. We detected 117 different chemicals in water, sediment, and/or fish in wastewater effluent-impacted, developed, and undeveloped sites. Chapter 3 prioritizes the chemical hazards of the detected chemicals through a rapid assessment of chemical-specific information - including detection frequency, persistence, endocrine disruption, toxicity, and bioaccumulation - to evaluate the potential for these contaminants to cause adverse effects on aquatic life. We identified 50 contaminants in water, 21 in sediment, seven in fish as high priority, including antimicrobials, antihistamines, antidepressants, cardiovascular modulating agents, and insect repellant. Chapter 4 evaluates the health of wild fish exposed to CECs across varying anthropogenic pressures. We compared the utility of three different approaches that could be used to evaluate the health of fish exposed to CECs: a refined fish health assessment index (rFHI), a histopathological index, and high-throughput (ToxCast) in vitro assays. We mapped adverse outcome pathways (AOPs) associated with identified ToxCast assays to determine potential impacts across levels of biological organization within the aquatic system. The health of fish in undeveloped sites was as poor, or sometimes poorer, than fish in developed and wastewater effluent-impacted sites. Chapter 5 is a general discussion to conclude the relevance of this work and explore important future directions. Collectively, this thesis provides evidence of the potential hazards of CECs and their impact on fish health in a region that is important for sustaining Indigenous culture through subsistence fishing.