Oysters aren’t just a tasty dish for a romantic evening. Scientists are turning to the creatures for a decidedly less sexy reason: to clean up polluted bays. Sponges, oysters, and mussels are excellent multitaskers. They feed by filtering water that rushes over them, pulling out the nutrients they need; in the process, the animals can remove pollutants and pump out cleaner water.

“In the US, we are mainly in the talking stage on the subject; there is not much in the water yet,” says Gary Wikfors, a microbiologist with the National Marine Fisheries Service. But that may change soon. In June, scientists from around the country will gather in Providence, Rhode Island, to discuss the future of shellfish aquaculture.

Researchers who support using the animals to remove pollutants from bays, lakes, and rivers do have a few concerns. One question being raised is whether shellfish that have been used to help clean a bay should be sold for human consumption. Another is whether the creatures will be able to survive in extremely polluted waterways. “It’s a mistake to think that just adding oysters or mussels is going to be enough anywhere,” says Jay Levine, a North Carolina State University College of Veterinary Medicine researcher responsible for leading the cleanup of North Carolina’s Wilson Bay. “But along with other approaches, bivalves can help restore waterways.” Here’s how these invertebrates are taking it all in.

Sponges:  Some 10,000 species of sponge inhabit fresh and salt waters, and a single sponge can filter hundreds of gallons of water per day. As aquatic restorers, the animals are perhaps best known for their ability to remove microorganisms, like those associated with fecal contamination. Researchers have found that a Mediterranean sponge, Spongia officinalis, can eliminate a wide variety of water pollutants, from bacteria to polychlorinated biphenyls (PCBs) to oil.

Oysters:  New York City’s Gowanus Canal, once a dumping ground for corpses and trash, is now home to 2,500 oysters. The shellfish, each of which can filter up to 50 gallons of water a day, are doing their small part to clean the murky waters. In North Carolina, a more extensive project is helping clean up Wilson Bay: Oysters are suspended near the water’s surface, where they pull out excess nutrients, preventing algal blooms that suck oxygen out of the water.

Freshwater Mussels:  The US Fish and Wildlife Service is identifying waterways nationwide that could be helped by freshwater mussels. The primary goal is to bolster dwindling populations (nearly 70 percent of freshwater mussels are endangered or threatened), but the creatures will also help pull nitrogen, heavy metals, PCBs, and other contaminants out of rivers and lakes. 

Story by Alisa Opar. This article originally appeared in Plenty in July 2008.

Copyright Environ Press 2008

Oyster cleanup brigade
Scientists are looking to sponges, mussels, and oysters to clean up polluted waterways