Can You Hear Me Now? How Fish Are Losing their Way in a Warming Ocean
Image courtesy of cadmanof50s via flickr
While many new studies investigating the links between global warming and the oceans continue to (understandably) focus on acidification and its harmful effects on corals, few so far have examined its direct impact on fish and other larger marine organisms. An interesting new article published in the journal Proceedings of the Royal Society attempts to do just that, suggesting that warming, more acidic oceans could be inhibiting the development of ear bones in juvenile reef fish - resulting in their getting lost at sea during a pivotal developmental stage.
A team of international researchers, led by AIMS' Monica Gagliano and Martial Depczynski, discovered that damselfish with asymmetrical ear bones, or otoliths, structures that allow them to find their way back to the reef by homing in on reef-specific sounds, had trouble finding their homes. They believe the otolith asymmetry is closely related to the double whammy of rising sea surface temperatures and higher acidity. Given that the juvenile fish depend on these hearing structures to locate a place on the reef to settle and breed, they are concerned that many will get stranded in the open ocean during their earlier developmental stage and likely die.
The scientists compare the fish's hearing system to a sophisticated navigation system - one that allows them to discriminate between a range of sound frequencies to home in on a particular signal. The development of otoliths, which, like fish skeletons, are made entirely from calcium carbonate (the main component of reef-building corals), is constrained by acidic waters; not only is there less calcium carbonate to go around, what is left is dissolving.
This latest bit of depressing news comes as a growing consensus of reef scientists is predicting that most of the world's coral reefs, including the majestic Great Barrier Reef, could be gone by 2050; a decline in fish biodiversity will likely only help accelerate the reefs' collapse.