Acid oceans leave fish at more risk from predators

BBC: Ocean acidification could cause fish to become "fatally attracted" to their predators, according to scientists. A team studying the effects of acidification - caused by dissolved CO2 - on ocean reefs found that it leaves fish unable to "smell danger".

The findings were published in the journal Ecology Letters. Danielle Dixson from James Cook University in Queensland, Australia, led the study. She and her colleagues tested orange clown fish larvae that were raised in water with the same slightly alkaline pH as their ocean reef habitat, and those raised in more acidic water. The team released the fish into a "flow chamber" with two water sources flowing in parallel.

One source was taken from tanks containing the clown fishes' natural predators and one was drawn from tanks in which non-predatory fish were swimming. "The flow rates are identical, so the water won't mix," Ms Dixson explained. "This allows the fish in the chamber to choose which water cue they prefer or dislike."

In the test, the fish reared in normal water avoided the stream of water that their predators had been swimming in. They detected the odour of a predator and swam away from it. But, Ms Dixson said, fish raised in the more acidic water were strongly attracted to both the predatory and the non-predatory flumes.

… Ms Dixson told BBC News: "Ocean acidification has the potential to become a widespread problem and it's unknown how many organisms and ecosystems will cope with the decrease [in] pH. "This study shows that ocean acidification could lead to an increase in the mortality of larvae."…

A clown fish, shot by Fir0002, Wikimedia Commons, under the terms of the GNU Free Documentation License, Version 1.2