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Reef fish act drunk in carbon dioxide–rich ocean waters

In first test in the wild, fish lose fear of predators’ scent

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4:17pm, April 14, 2014

SMELL NO EVIL  Young damselfishes (shown) living in carbon dioxide-rich waters have trouble detecting predator odors, compared to fish in areas with less CO2 dissolved in the water.  

Carbon dioxide can really mess with fishes’ heads. Dissolved in ocean water, the acidic chemical turns timid young reef fish into tipsy little daredevils, researchers report April 13 in Nature Climate Change.

The findings are the first to show that carbon dioxide makes fish in the wild act just as crazy as fish dosed with the greenhouse gas in the lab, says marine biologist Astrid Wittmann of the Alfred Wegener Institute in Bremerhaven, Germany, who was not involved with the new work.

“These are pretty major behavioral changes,” she says. “They’re absolutely surprising.”

As carbon dioxide pours into the atmosphere, the gas filters down into oceans, slowly but steadily dialing up the waters’ acidity. In laboratory tests, fish exposed to carbon dioxide–infused waters have hearing and learning problems and odd behavior issues: They seek out predators’ odors.

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