Effects of ocean acidification on the Life-History and Behaviour of Tropical Marine Fishes

Chair: Martin Grosell

Philip Munday (1)

1 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4814 Australia

Background
Experimental studies with tropical species have been at the forefront of testing the effects of ocean acidification on marine fishes. In this talk I will review and synthesize the results to date and provide directions for future research.

Findings
With some exceptions, basic life-history traits such as growth and development appear to relatively unaffected by projected future CO2 levels, at least in the reef fishes tested to date. Reproductive output may even been enhanced in high CO2. However, near-future CO2 levels interfere with sensory functions and behaviours in tropical marine fishes. Changes include increased activity and boldness, impaired decision making, inability to learn, and altered auditory, visual and olfactory preferences. These sensory and behavioural changes affect a range of critical ecological processes, including predator-prey and competitive interactions, navigation and habitat selection. The underlying mechanism responsible for sensory and behavioural effects appears to be interference of elevated CO2 with brain neurotransmitter function, a previously unrecognized threat of ocean acidification. Furthermore, there appears to be limited capacity for within and between generation acclimation of behaviour to high CO2, which contrasts with findings for life history traits.

Conclusions
Behavioural effects of rising CO2 levels may be a more immediate threat to tropical marine fishes than physiological effects of high CO2 on individual life-histories. Determining the relationship between physiological and behavioural sensitivity to high CO2, and the potential for adaptation of behaviours to rising CO2 levels, will be key to predicting the effects of ocean acidification on marine fish populations.