PROVIDENCE, R.I. [Brown University] A marathon summer of field work by Mark Bertness, professor of ecology and evolutionary biology, and a squadron of students may finally help settle the heated debate about what's killing the coastal saltmarshes of southern New England and Long Island. The group's work has yielded two new papers that offer clear evidence of the cause.
In one paper, published March 20 in the journal PLoS ONE, they provide the results of numerous measurements at 14 sites around Rhode Island's Narragansett Bay. They sought correlations between the exent of marsh death and evidence of any of several popular hypotheses. The winner by far was runaway herbivory of cordgrass by the Sesarma crab. In the other study, published April 28 in the journal Ecology Letters, they directly tested that hypothesis with experiments on Cape Cod. The results were that wherever they protected Sesarma from the pressure of predators, the crabs ruthlessly mowed the grasses down.
Both papers back up the explanation that Sesarma are ravaging the marshes because overfishing has reduced the predators that would naturally keep the crabs in check. Long-held beliefs that physical forces, rather than disrupted food webs, are killing the marshes just aren't true, Bertness said.
"These are very deeply embedded paradigms and dogma," Bertness said. "But the conservation implications of this are enormous, so at some point in time people have to set that aside and look at this objectively."
(Also last month, the team published another paper in PLoS ONE estimating the carbon that may have been freed from sequestration because of the marsh loss)
A summer of salt, crabs, and mud
Bertness' team included lab manager Caitlin Brisson, seniors Matt Bevil and Sinead Crotty, and junior Elena Suglia. They divided their time between Rhode Island and Cape Cod from May to August, often worki
|Contact: David Orenstein|