Ocean acidification may make fish foolhardy

Rising carbon dioxide may rob fish larvae of their ability to sense predators and survive

Baby fish become confused and reckless in water with high levels of dissolved carbon dioxide, a new study shows. This leads to higher death rates and may mean that rising atmospheric carbon dioxide, which causes ocean acidification, will reduce the number of fish in the ocean.

“It shows we should be concerned with even minor changes in aquatic ecology, because it’s going to have dramatic effects on the survival of fish,” says Grant Brown, a freshwater behavioral ecologist at Concordia University in Montreal who was not involved in the study. “There are very fine-scale, yet extreme critical effects going on.”

Atmospheric carbon dioxide levels are projected to rise over the next century from fossil fuel burning. As carbon dioxide enters the Earth’s atmosphere, some of it is absorbed into oceans. The CO2 dissolves, as it does in carbonated beverages, and lowers the water’s pH. A lower pH is known to hinder the ability of oysters and other marine life to build calcium carbonate shells, but effects on fish are less well-known.

Marine ecologist Philip Munday of James Cook University in Townsville, Australia, and his colleagues showed previously that high levels of dissolved CO2 interfere with the sense of smell of clown fish. The larvae of clown fish and other coral reef fish rely on their sense of smell to stick close to home and avoid predators.

Gwyneth Dickey, ScienceNews, 6 July 2010. Full article.

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