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Oysters Used to Restore US Coasts

US - long the U.S. coasts, scientists and conservations are increasingly looking to oysters to help filter water, bolster species diversity, and prevent erosion.

According to Audubonmagazine mall-scale restoration projects that incorporate oyster aquaculture are currently under way in 15 states, including New York, North Carolina, Louisiana, and Washington. Federal, state, and local governments, along with nonprofit conservation groups like The Nature Conservancy, the Chesapeake Bay Foundation, and Massachusetts Audubon, are funding the programs—and seeing some promising results.

Audubonmagazine says that a century ago oysters covered extensive sections of both the Atlantic and Pacific coasts. "The formed massive reefs, often protruding from the water at low tide; in one case, off Long Island, a lighthouse was built directly on top of one such reef", says the organisation. Oysters became increasingly desirable as food during the 1800s, and people plucked them from intertidal zones by the billions. Studies show that in Virginia and Maryland alone, oystermen harvested 20 million bushels a year in the 1870s. The practice proved to be unsustainable, and oyster numbers dropped drastically after a decade. Increased pollution, disease, and loss of habitat contributed to their decline. In Chesapeake Bay, populations today are only one percent of what they were at their peak.

The plummet in oyster populations, coupled with runoff into waterways of nutrients, such as phosphorus and nitrogen, from agricultural and development, have led to many unbalanced coastal ecosystems. Nutrient enrichment spurs the prolific growth of algae, which blankets the surface of the water and makes it look like pea soup. Those algal blooms subsequently block light from reaching the organisms below the surface and deprive the water of oxygen. In the most extreme circumstances, such conditions lead to dead zones, where no organisms can survive. The number of dead zones has doubled nearly every decade since the 1960s, according to a study published this summer in Science.

To reduce nutrient overload, some scientists are now reintroducing oysters to areas where they once thrived, an idea that conservationists put into action in the mid-’90s, says Robert Brumbaugh, the director for the restoration program at The Nature Conservancy. Oysters were a natural fit, considering how some species can filter up to 50 gallons of water a day and digest and absorb nitrogen in the process. “It’s like putting sheep out into an overgrown field,” says Bill Walton, a fisheries and aquaculture specialist at the Cape Cod Cooperative Extension and Woods Hole Sea Grant program.