A proportion of carbon dioxide produced by burning fossil fuels gets absorbed by the ocean, which is gradually making it more acidic. Recent studies have shown that this can cause fish to lose their sense of smell but the new research shows that fish hearing is also compromised. Scientists at the University of Bristol reared clownfish larvae in different CO2 environments and then played them realistic noises corresponding to typical clownfish predators.
As lead author Dr Steve Simpson explains “We kept some of the baby clownfish in today’s conditions, bubbling in air, and then had three other treatments where we added extra CO2 based on the predictions from the Intergovernmental Panel on Climate Change for 2050 and 2100. Fish reared in today’s conditions swam away from the predator noise, but those reared in the CO2 conditions of 2050 and 2100 showed no response."
The ability of fish to adapt to changing conditions is not known. Dr Simpson said: “What we have done here is to put today’s fish in tomorrow’s environment, and the effects are potentially devastating. What we don’t know is whether, in the next few generations, fish can adapt and tolerate ocean acidification. This is a one-way experiment on a global scale, and predicting the outcomes and interactions is a major challenge for the scientific community."