MicroRNA and multiple stressors: A mechanistic approach to understanding environmental stressor impacts in fish.

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Worldwide rivers, lakes, and oceans face extensive and complex threats to water quantity and quality both in the short and long term. The growth of urban centres and the increased use of our water resource means lost and changed habitats and accompanying changes in species composition, and increased levels of aquatic contaminants from wastewater and agricultural runoff. These numerous threats are not independent but work cumulatively to alter our ecosystems. Our aquatic environments and the water supplies that depend on them must remain healthy to ensure ecosystem sustainability. However, our ability to do so is limited by our capacity to understand and predict how the various stressors resulting from these threats interact to cause change. While each of these challenges poses documented problems for aquatic ecosystems and affects everyone using these bodies of water, the concern is that combinations of these effects will create even more significant challenges to these environments and, more specifically, aquatic organisms living in them. Many regulations, policies, monitoring and remediation programs are based on an understanding of only single factors (e.g., one specific pollutant) and are therefore inadequate. Based upon this, my research program is focused on expanding our fundamental understanding of the impact of multiple, mixed stressors, found within the environment upon epigenetic mechanisms in aquatic species, specifically teleost fishes. By taking an integrative approach spanning from DNA to whole animal function and fitness, my research program focuses on epigenetic modulators, like microRNA (miRNA), that drive the adaptive or maladaptive phenotypes presented by zebrafish that have been exposed to multiple stressors (emerging contaminants/climate stressors). My research will focus on abiotic factors associated with climate change (temperature) in combination with an emerging organic pollutant (venlafaxine, a major pharmaceutical pollutant of concern), which have been shown to impact numerous fish species. This novel approach will uncover the miRNA mechanisms associated with mitochondrial disruption that we have previously seen with mixed stressor exposures. Moreover, taking a sex-specific approach, we will identify the male and female contributions of miRNA and their influence on their progeny, which will provide some of the first evidence of how sex-specific (male vs female), adult life-history exposure to environmental stressors can influence offspring in future generations. The results generated through my program will aid in the identification of energetic and sex-specific miRNA biomarkers, which are translational to key sentinel and economically important species in Canada, such as salmonids, and identified biomarkers will be used by conservation managers to assess and predict the impact of mixed stressors in sensitive watersheds for the protection of Canada's freshwater species.