Ocean Dumping that Restored Marine Life

Dumping half a million tons of shells into the Gulf of Mexico sounds like the opposite of environmental restoration. But along Florida’s Gulf Coast, discarded oyster and clam shells have been put back into the water as part of efforts to rebuild oyster reefs. The basic idea was surprisingly simple: instead of sending mountains of shells from restaurants and seafood processors to landfills, they could be used as the hard surface that young oysters need to settle on. Oyster larvae can’t establish themselves on shifting sand or mud, but they can readily attach to hard shells and begin building a new reef.

That’s exactly what happened. The shells were placed in parts of the Gulf where oyster reefs had been severely damaged or had disappeared because of overharvesting, pollution or environmental disasters. Once the shells accumulated on the seabed, they became the foundation for new oyster colonies. Young oysters began attaching themselves to the recycled shells. As generation after generation attached to the growing reef, the pile of discarded shells became a living structure.

Oysters do much more than provide seafood for humans: an adult oyster can filter as much as 50 gallons of water a day, removing suspended particles and helping improve water clarity. Reefs also create hiding places and feeding grounds for hundreds of other marine species. This restoration effort led to a notable rebound in fish, sea turtle and dolphin populations. The new reefs also strengthened coastal defenses against storms by reducing wave energy before it reaches the shoreline.

In Florida’s Suwannee Sound, the Lone Cabbage restoration project rebuilt more than three miles of oyster reef. After several years, commercial harvesters were finding legal-size oysters on and around portions of the restored reef. Researchers concluded that the problem had not been a shortage of oyster larvae—it was a shortage of suitable places for those larvae to attach and grow. All they needed was the right foundation and the oysters could rebuild the reef themselves.