01 September 2011

Clownfish risk going deaf

The charming little clownfish - known by many from the film Finding Nemo - is at risk of becoming deaf if the pH-level in the oceans continues to fall.

Since the Industrial Revolution, over half of all the CO2 produced by burning fossil fuels has been absorbed by the ocean, making the pH-level drop faster than ever and resulting in ocean acidification.

An international study shows, that ocean acidification within the next few decades could threaten the clownfish's ability to hear. For baby clownfish, the ability to hear is crucial, as it makes them able to detect and avoid predator-rich coral reefs during the daytime.

The study

The research team made their findings after analysing larvae reared straight from hatching in different CO2 environments.

Lead author Dr Steve Simpson from the University of Bristol 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.” Dr. Steve continues: “We designed a totally new kind of experimental choice chamber that allowed us to play reef noise through an underwater speaker to fish in the lab, and watch how they responded.”
After 17-20 days rearing, the researchers monitored the response of the juvenile clownfish to the sounds of a predator-rich coral reef, consisting of noises produced by crustaceans and fish. “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,” Dr. Steve says.

However, it remains to be seen whether fish species will adapt to the new conditions or not. The new generations of fish might adapt to the ocean acidification.

What about human hearing?

It is not just water that changes as the globe's CO2-content rises. The composition of the air is also affected by the rising CO2-emissions. Whether this can have consequences for human hearing can only be guessed.

Source: http://cordis.europa.eu & www.bristol.ac.uk

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