60-Second Earth

Fish Smell Badly in More Acidic Oceans

Some fish living in waters with currently naturally high levels of CO2 lose their sense of smell, and with it their ability to perceive predators—a possible portent to a global situation in the near future. David Biello reports


Rising levels of carbon dioxide are already souring the world's oceans. Globally, seawater has become 26 percent more acidic since the 19th century because of additional CO2.
That's bad news for organisms like coral and plankton that need to form structures made of calcium carbonate and other minerals, because there’s less carbonate in a more acidic ocean.  But it's also bad news for fish.
Previous lab experiments had shown that fish living in high-CO2 waters lost their sense of smell. That deficit caused them to lose their natural avoidance reaction to predators—an obvious challenge for survival.
So scientists looked at fish that live on coral reefs near spots where CO2 naturally bubbles out of the seafloor near Papua New Guinea.
The researchers found the same impaired smell—and risky behavior—in the wild fish on reefs near the CO2 seeps. But the same species of fish in regions with more normal acidity maintain a healthy fear of being eaten. The study is in the journal Nature Climate Change. [Philip L. Munday et al, Behavioural impairment in reef fishes caused by ocean acidification at CO2 seeps]
The research team is now examining whether fish can adapt to more acidic waters. Otherwise, our crazy environmental impacts may make them increasingly reckless.
—David Biello
[The above text is a transcript of this podcast.]
[Scientific American is part of the Nature Publishing Group.]

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