We took a boat ride to Little St. Simons Island on Georgia’s coast the other day to learn how recycled oyster shells — discards from restaurants, seafood packers and oyster roasts — are being used to help keep our superb salt marshes healthy and intact.
It’s a new effort called “living shorelines,” in which oyster reefs and native marsh plants (such as Spartina) replace unsightly “armored structures” (such as seawalls and bulkheads) to prevent erosion along tidal creek and river banks.
The old shells are packed into mesh bags about the size of flour sacks and — after much pre-planning — are carefully placed along banks where erosion threatens to gnaw away the salt marsh and adjacent upland. The motivating idea is that the old shells will become the foundation of new oyster reefs, which, in effect, will serve as natural breakwaters.
Oyster reefs form naturally when free-swimming larval oysters called spats adhere firmly to old shells. As the spats mature into adults, they attract more spats and the process continues until a living reef forms.
The reefs are essential to salt marshes. In addition to erosion control, they filter and cleanse huge volumes of water and provide vital habitat for many fish species and other marine creatures.
Living shorelines also serve those functions. “They mimic nature,” said biologist Jan MacKinnon of Georgia’s Department of Natural Resources. In addition, they are pleasing to the eye because they blend into the environment.
Little St. Simons’ managers decided last year to replace 1,000 feet of a failing wooden bulkhead along scenic Mosquito Creek with a living shoreline. To do that, they put down 10,000 bags of oyster shells and planted native marsh plants, whose roots also stymie erosion.
Scott Coleman, the island’s ecological manager, said the shells already are attracting spats, and fish diversity in the creek is increasing.
In the sky: Winter officially begins at 6:03 p.m. Sunday — the shortest day of the year. The Ursid meteor shower, visible through Thursday, reaches a peak Sunday night of about 15 meteors per hour, said David Dundee, Tellus Science Museum astronomer. Look to the east from about midnight until dawn. The moon is new Saturday. Venus is low in the west just after dark. Mars is low in the southwest at sunset and sets about an hour later. Jupiter rises out of the east a few hours after dark. Saturn is very low the east just before dawn.
