Exploring how climate change impacts the intersection of immunity and temperature in hypoxia-tolerant pacific fish and sharks

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Environmental hypoxia (i.e., limited oxygen) is a condition that can be lethal to animals. Many fish are exposed to aquatic hypoxia in the ocean or in intertidal pools. Alarmingly, climate change is increasing the frequency and severity of hypoxic events and the size of hypoxic regions in aquatic environments. In the past few decades, increases in aquatic temperatures exacerbated by global warming correlate with decreasing oxygen content in oceans, and particularly in coastal regions that support marine aquaculture. As a consequence, aquatic hypoxia due to global warming is expected to worsen with the acceleration of the climate crises and poses a significant challenge to coastal marine populations and aquaculture globally.For all animals, a properly functioning immune system is crucial for survival, and key to the ability of fish to resist infection by bacteria and viruses and to heal after injury. Immune responses are impaired by hypoxia and by high temperatures and thus aquatic animals may be immunocompromised by the progression of global warming and increasing incidence of aquatic hypoxia. Despite the environmental challenge posed by aquatic hypoxia, some species have adapted strategies to ensure their survival when oxygen is limited. Of particular interest are sharks that inhabit intertidal pools in tropical regions where they are exposed to periods of severe hypoxia in combination with high water temperatures. These hypoxia-tolerant fishes provide an excellent model to investigate interactions between adaptations that favour hypoxia-tolerance vs. immunity.Our OBJECTIVES are to determine 1) whether hypoxia activates an immune response in hypoxia-tolerant and -intolerant sharks, 2) whether immune system activation compromises adaptive physiological responses to hypoxia in hypoxia-tolerant sharks, and 3) whether hypoxia compromises immune competency. Our collaborators provide access to these key study species and this research would be impossible without them.