Ocean Acidification Effects Fish Behavior and Survival as a Consequence of Impaired Chemoreception

Anthropogenic induced changes to the environment threaten many natural processes and ecosystems.  Human activities such as land-use changes and the combustion of fossil fuels have caused an increase in the amount of CO₂ in the atmosphere.  Approximately 30% of the additional CO₂ produced by humans over the past 250 years has been absorbed by the oceans.  While ocean acidification is predicted to threaten marine biodiversity, the direct effect it will have on marine organisms remains speculative.  Here, I discuss laboratory and field-based experiments designed to test the effects of ocean acidification on larval coral reef fishes.  Dramatic changes were observed in the behavior of larvae when exposed to seawater treated with CO₂-enriched air (simulating scenarios predicted in the next 50-100 years).  Larval fish reared in control seawater discriminated between a range of chemical cues used for settlement site selection and predator avoidance, however discriminatory ability was impaired in larvae reared elevated CO₂conditions.  Larvae exposed to elevated CO₂ were more active, exhibiting riskier behavior in natural coral-reef habitats; resulting in markedly higher mortality from predation than current-day controls, with mortality increasing with CO₂ concentration.  The disruption of larval behavior could have profound effects on population replenishment and connectivity patterns of many marine species.