When a good salt marsh goes bad, voracious snails finish off the job, new research reveals.
Periwinkle snails ordinarily live in ecological harmony with salt marshes, eating only dead cordgrass and a fungus that grows on the plants.
But when salt marshes are stressed by drought, snails graze by the millions in a feeding frenzy that mows down the living plants.
During the past six years, salt marshes in the southeastern United States—in Georgia and Louisiana especially—have experienced unprecedented die-offs.
Wetlands help protect coastal areas from storm surges and flooding brought by tropical storms and hurricanes.
More than 250,000 acres (100,000 hectares) have been lost, mostly due to a severe drought that peaked between 1999 and 2001.
But periwinkle snails also played a role, says Brian Silliman, study author and University of Florida, Gainesville ecologist.
"The snails finish [the salt marsh] off," he said. "They graze it down and completely kill it, change the marsh from a green habitat to a brown habitat," he said.
Silliman and colleagues describe their study in today's issue of the journal Science.
Cheese and Crackers
Periwinkle snails feed on a diet of dead marsh grass and fungus that Silliman likens to "cheese and crackers."
"The plant provides the carbs, and the fungus is the protein and fat," he said. "If [the snails] don't get that 'cheese,' they don't grow."
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