Ocean acidification

Abstract Ocean acidification describes the decline in pH of marine environments as they continue to absorb anthropogenically-derived carbon dioxide (CO2). Research over the past ~15 years has reported that levels of ocean acidification forecasted for the end of the century (CO2 ~800–1000 µatm; pH ~7.6–7.7) can severely impair behaviours of marine animals, including fishes and invertebrates. Impaired behaviours of most concern are those linked with neural and sensory systems, such as the capacity to respond appropriately to predators. However, after an initial proliferation of studies reporting dire behavioural disturbances, studies finding negligible effects of end-of-century ocean acidification began to accumulate. We have now reached a point where there is little consensus on whether, and how much, ocean acidification will impact animal behaviour. Here, we outline existing knowledge regarding the effects of ocean acidification on animal behaviour, discuss the chronology of discoveries and controversies in the field, and provide guidance for improving rigour and transparency in behavioural ecology more broadly.