Biology Letters Study - Ocean Acidification Already Disrupting Shellfish Defensive Behaviors

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Simon Rundle and colleagues from the University of Plymouth in England conducted a different kind of study, looking for indirect effects on behavior. Their work, published in Biology Letters, shows that increasing acidity disrupts the defense mechanisms of the common periwinkle, Littorina littorea.

These sea snails, Dr. Rundle said, respond to the presence of crab predators by doing one of two things: thickening their shells (to better withstand the crush of a crab claw) or practicing “avoidance behavior,” crawling out of sight. Shell-thickening is believed to be initiated when the snails sense some chemical cues in the water emitted by the crabs.

Dr. Rundle and his colleagues found that more acidic seawater, on its own, had no effect on shell thickness. But when crab cues were introduced, snails in normal water increased shell thickness markedly. In more acidic water the process was disrupted, and little or no thickening occurred. “The important thing we found is that until you start looking at these defenses, you don’t see an effect of this ocean acidification,” Dr. Rundle said.

The researchers found that periwinkles in the more acidic environment increased their avoidance behavior. “There’s almost this idea of a tradeoff,” Dr. Rundle said. “Because the thickening wasn’t there, they were then ‘deciding’ to use avoidance.” That, in turn, may affect how the snails interact with other marine life. So a “simple” increase in acidity may have a not-so-simple impact on ecosystems.

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http://www.nytimes.com/2007/11/06/science/06obsnai.html?_r=1&ref=science&oref=slogin