Grazing Snails Mow Down Salt Marshes

Grazing snails like the periwinkle snail pictured above are killing off salt marshes in the Southern United States, according to a recent study.

Brian Silliman from the University of Florida, Gainsville and colleagues surveyed over 1200 kilometers of coastline in Georgia and Louisiana and found high densities of plant-grazing snails -- up to 1500 snails per square meter -- mowing down cordgrass (Spartina alterniflora) and other marsh plants at 11 of 12 marsh die-off sites.

While the die off is thought to have started as a result of drought stress, the snails are exacerbating the problem by spreading from the edges of the die-off zones to the remaining healthy areas and converting marshes into exposed mudflats. The researchers warn of further degradation and possible collapse of the environmentally and economically critical costal ecosystems if conservation steps are not taken soon.

The finding was detailed in the Dec. 15 issue of the journal Science.

--Ker Than

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Credit:  Brian Silliman