How mussels could help clean polluted waters
Along the shores of New York Harbor, scientists are investigating whether mussels, a hardy bivalve, might be grown in urban areas as a way of cleaning coastal waters of sewage, fertilizers, and other pollutants.
Not long ago, a boatful of shellfish researchers and I cruised downstream toward a most unlikely structure bobbing at the mouth of one of the most urban bodies of water on the planet.Skip to next paragraph
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The 20-foot by 25-foot form ahead of us was an experimental raft that scientists from the US National Oceanic and Atmospheric Administration (NOAA) had placed at the mouth of New York City’s Bronx River last spring. Hanging beneath it were long, sock-like tendrils that had been seeded with Geukensia demissa, commonly known as ribbed mussels. The point of the two-year experiment was to see whether mussels would survive or even thrive given the industrial and organic effluent that flows from the Bronx into the greater New York Harbor. If the mussels did in fact prosper in this environment, it could have implications for how we might help clean up coastal waters in various parts of the world.
The idea of using bivalves like mussels, oysters, and clams to purify waterways has been on the minds of conservationists and scientists for decades. Perhaps because of a romantic nostalgia for the lost, billion-strong oyster colonies that once girded the coasts of the eastern US, millions of dollars have been put into oyster restoration projects, to mixed effect. But as mussel aquaculture grows in the US, Canada, and elsewhere, businessmen and scientists are increasingly considering the mussel, both as a way to produce a commercial product and to explore their potential as water filterers.
Uppermost on the minds of the researchers out on the Bronx River — a joint project of NOAA and the Long Island Sound Study — was whether certain types of mussels could be used to rid coastal waters of an onerous influx of nitrogen generated from sewage, fertilizers, and other pollutants. This “nutrient loading” can prompt algal blooms, which in turn deprive coastal waters of oxygen when the algae die and decompose.
“In areas where water quality is degraded... from nutrient over-enrichment, the ribbed mussel looks like a dependable partner to help us recycle lost nutrients back into useful products,” Gary Wikfors, an aquaculture expert and chief of the biotechnology branch at NOAA’s laboratory in Milford, Conn., said in an e-mail.
Other researchers also are investigating the beneficial effects of raising seaweed and kelp, in conjunction with bivalves, to clean coastal waters.
In macro-ecological terms, mussels and their bivalve kin are the intestines of coastal ecosystems. Their filters remove organic particulate matter from the water column, particularly phytoplankton. Oysters were long the bivalve of choice in the US, but the mussel has certain advantages that are being increasingly touted. Although an individual oyster can filter much more water — an estimated 20 to 30 gallons per day — mussels grow more densely than oysters.
Carter Newell, the founder of Pemaquid Mussel Farms in Damariscotta, Maine, and who had joined us on the Bronx River raft, explained that mussels do something that oysters in their present state of depletion don’t: They work in three dimensions. Oysters once built tremendous vertical reefs, many feet high, that accrued over centuries in places like the Chesapeake Bay and Long Island Sound. But those wild reefs are mostly gone, and the time needed to rebuild them to a useful height is formidable. Meanwhile, mussel rafts, with their long tendrils of bivalves, can be immediately established in 3D, working throughout the water column at incredible densities.