Ocean acidification leaves clownfish deaf

Ocean acidification could threaten the safety of baby clownfish say researchers in Bristol, who believe increasing amounts of carbon dioxide in the ocean is playing havoc with the fish’s senses.

Recent studies have  shown that ocean acidification is responsible for fish losing their sense of smell, but Dr Steve Simpson from the University of Bristol and Professor Philip Munday of James Cook University have shown that it may also compromise their ability to hear.

Clownfish use hearing to detect and avoid predator-rich coral reefs during the day, so Simpson and Munday reared clownfish larvae straight from hatching in differing CO2 environments – today’s conditions, and those predicted for 2050 and 2100.

“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 prediction from the Intergovernmental Panel on Climate Change,” said Simpson.

After 17-20 days, Simpson monitored the response of his juvenile clownfish to the sounds of the predator-rich coral reef – noise from crustaceans and fish. Those reared in today’s conditions swam away from the noise, but fish reared in future conditions showed no response.

The ears of fish are buried deep at the back of their heads, and this research suggest lower pH conditions may have a profound effect on the entire functioning of the sensory system. Researchers hope that future generations of fish will actually adapt to and tolerate the increasingly acidic ocean, although it is not known if they will.

“What we have done here is to put today’s fish in tomorrow’s environment, and the effects are potentially devastating,” said Simpson. “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.”