Ecology: Reassessing impacts of ocean acidification on fish behaviour

Ocean acidification due to rising CO₂ levels may have a negligible impact on critical behaviours of coral reef fishes, reports a paper published in Nature. The findings, which challenge previous research, are the results of a multi-year, multi-species project aimed at assessing the impact of ocean acidification on coral reef fishes.

By the end of the century, the acidification of the oceans is expected to exceed what the planet has experienced in the past 30 million years, which has sparked concerns for the stability of marine ecosystems.

Previous research has suggested that ocean acidification will affect the behavioural and sensory capacity of coral reef fishes; however, there are disparities in results between studies, even when species and methods are similar. Timothy Clark, Josefin Sundin and colleagues tested the reproducibility of previous reports in a three-year study of over 900 individuals of six different fish species in both wild and tank settings. They examined predator avoidance, activity levels and behavioural lateralization (favouring one side of the brain during activities) and found that increased acidification does not impact these critical behaviours of coral reef fishes.

The scale and scope of this study, compared with previous reports, may explain the differing conclusions. The authors encourage future replication of investigations into the effects of rising CO₂ levels on fish behaviours. They also stress that the increasing atmospheric CO₂ is linked to ocean warming, which is having a profound effect on marine fishes.

doi: 10.1038/s41586-019-1903-y

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