The Physiological and Behavioral Responses of Subtropical Nearshore Fishes to Climate Change

Global climate change is expected to increase the mean CO₂ concentrations in the oceans by ~250 µatm in the next 100 years, and increase the frequency and intensity of tropical storms that will result in larger pulses of rainwater and by extension CO₂ into the nearshore ecosystem.  Together, the mean and extreme CO₂ levels are expected to increase in the nearshore environment, yet very little research has been conducted on fish in this ecosystem.  To address this lack of information, the CO₂ tolerance limit across seasons, performance costs, and avoidance of elevated CO₂ concentrations in the presence and absence of a predator were evaluated for yellowfin mojarra, schoolmaster snapper, checkered puffer, and bonefish.  Checkered puffer experienced an increase standard metabolic rates when exposed to CO₂ concentrations that coincide with and exceed the worst case scenario.  Checkered puffer and yellowfin mojarra exhibited a higher CO₂ tolerance in the summer than in the winter.  Checkered puffer shuttled (i.e., moved to ambient seawater) at a higher CO₂ level in the presence of a predator.  Overall, a species-specific physiological and behavioral response to elevated CO₂ levels will result in a slow restructing of the nearshore fish community.