The 74,000-acre Guana Tolomato Matanzas National Estuarine Research Reserve, a marine sanctuary in St. Johns County, is under threat from coastal erosion. Thankfully, resident biologists have come up with an ingenious solution: recycled oyster shells. Harvested from various sources, these shells are embedded in the shoreline to serve as a barrier between the reserve’s fragile banks and powerful, erosion-causing waves. The shells also promote the growth of new oysters, which filter seawater and increase biodiversity.
Seafood Restaurants Supplied Truckloads of Shells
The oyster shell recycling program began when the reserve’s researchers started collecting discarded oyster shells from nearby restaurants. They arrived by the truckload. The Tolomato River was the destination of these shells, which were piled along the shoreline. They were first stored in hole-filled plastic bags, but the non-degradable plastic component was deemed unsuitable for the project, so researchers turned to more eco-friendly storage methods.
The oyster shells are now joined together with water-safe concrete. The resulting structures resemble artificial reefs, which become less artificial when live oysters take up residence. The concrete method was preceded by one in which the shells were placed in metal cages called gabions. However, this too was scrapped after researchers realized that the metal would corrode and weaken the bars. In such an event, the gabions would have to be removed en masse. The best case scenario would be for the researchers to arrange a scrap metal pickup to recycle the corroded gabions. Either way, gabions would have required much more work than the concrete method, whose nickname “living shoreline” is a testament to its success.
Single Oyster Can Filter 50 Gallons of Water
“Living shoreline” refers to the live oysters who make their way into the concrete structures. Oyster shells are reusable; baby oysters will attach to shells that other oysters have vacated. Thus, in addition to protecting the coast from damaging waves, the recycled oyster shells provide homes for living oysters and attract other organisms, creating an ecosystem unto themselves. The living oysters provide one benefit that oyster shells do not: water filtration. One oyster can filter 50 gallons of water in a day, so imagine how much filtration an entire reef can achieve.
Recycled oyster shells are serving as artificial reefs in Florida’s Guana Tolomato Matanzas National Estuarine Research Reserve. Not only do they protect the shoreline from erosion; they filter the water and provide a habitat for plenty of species. Similar oyster shell recycling programs have been established in coastal states that include Texas, South Carolina and Delaware.