Couturier, Christine S., Stecyk, Jonathan A.W., Rummer, Jodie L., Munday, Philip L., and Nilsson, Göran E. (2013) Species-specific effects of near-future CO₂ on the respiratory performance of two tropical prey fish and their predator. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 166 (3). pp. 482-489.

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Abstract

Ocean surface CO₂ levels are increasing in line with rising atmospheric CO₂ and could exceed 900 μatm by year 2100, with extremes above 2000 μatm in some coastal habitats. The imminent increase in ocean pCO₂ is predicted to have negative consequences for marine fishes, including reduced aerobic performance, but variability among species could be expected. Understanding interspecific responses to ocean acidification is important for predicting the consequences of ocean acidification on communities and ecosystems. In the present study, the effects of exposure to near-future seawater CO₂ (860 μatm) on resting (M˙O₂rest) and maximum (M˙O₂max) oxygen consumption rates were determined for three tropical coral reef fish species interlinked through predator–prey relationships: juvenile Pomacentrus moluccensis and Pomacentrus amboinensis, and one of their predators: adult Pseudochromis fuscus. Contrary to predictions, one of the prey species, P. amboinensis, displayed a 28–39% increase in (M˙O₂max) after both an acute and four-day exposure to near-future CO₂ seawater, while maintaining (M˙O₂rest). By contrast, the same treatment had no significant effects on (M˙O₂rest) or (M˙O₂max) of the other two species. However, acute exposure of P. amboinensis to 1400 and 2400 μatm CO₂ resulted in (M˙O₂max) returning to control values. Overall, the findings suggest that: (1) the metabolic costs of living in a near-future CO₂ seawater environment were insignificant for the species examined at rest; (2) the (M˙O₂max) response of tropical reef species to near-future CO₂ seawater can be dependent on the severity of external hypercapnia; and (3) near-future ocean pCO₂ may not be detrimental to aerobic scope of all fish species and it may even augment aerobic scope of some species. The present results also highlight that close phylogenetic relatedness and living in the same environment, does not necessarily imply similar physiological responses to near-future CO₂.

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