Grant: Discovery Grants Program - Individual

Aquatic environments can vary considerably in abiotic conditions such as salinity, pH, dissolved oxygen, and temperature across spatial and temporal scales. Aquatic organisms inhabiting these environments must adjust physiological systems to match prevailing conditions if they hope to survive. Despite nearly a century of research in fish ecophysiology, several knowledge gaps remain in our understanding of developmental, mechanistic, and evolutionary physiology that limit our capacity to predict how wild populations will respond to forecasted environmental change. My research program will use two ecologically important fish species in Atlantic Canada, the mummichog (Fundulus heteroclitus) and banded killifish (Fundulus diaphanus), to address three questions that will deepen our understanding of the ecophysiology of wild fishes. How and why does salinity tolerance change over development? Adult mummichog are euryhaline and thus tolerate a wide range of salinities using mechanisms that have been well-characterized. However, embryos and larvae are less euryhaline, but the reason for reduced salinity tolerance is unclear. I will use an integrative approach applying physiological, molecular, and genetic techniques to understand why euryhalinity differs across life history. Moreover, because salinity tolerance may be a function of developmental differences in respiratory or cardiovascular capacity, I will explore how euryhalinity is influenced by exposure to relevant stressors (temperature, dissolved oxygen) that further challenge these systems. How do specific gene products contribute to physiological plasticity? Beneficial physiological plasticity can allow organisms to adjust homeostatic mechanisms to match changing conditions and is therefore a critical feature of organisms that inhabit variable environments. Euryhalinity, like other plastic traits, is a function of underlying gene products (i.e., proteins) that form mechanisms which can be fine-tuned to meet environmental demands. For example, acclimation to freshwater or seawater is often dependent upon the differential regulation of specific Na+/K+-ATPase isoforms in the gills. I will test whether these environmentally regulated gene products are critical to euryhalinity and other plastic traits using CRISPR/Cas9 gene knockout. How does local adaptation contribute to the invasion of harsh environments? Many naturally acidic water bodies in Atlantic Canada host fish populations even though the low pH conditions pose a significant physiological challenge. Using banded killifish as a study species, I will test the hypothesis that acid tolerance has evolved in acidic environments through the process of local adaptation. Protection of physiological diversity is a key goal of conservation biology, and this work will shed light on the evolution of physiological traits that lead to this diversity. My goal is that this research may help predict impacts of anthropogenic acidification.