Paul Greenberg, author of the James Beard Award winning New York Times bestseller Four Fish: The Future of the Last Wild Food, details a time in which he and a boatful of shellfish researchers cruised downstream toward as most unlikely structure: ‘The 20-foot by 25-foot form ahead of us was an experimental raft that scientists from the U.S. 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.’ Sounds more like a Doctor Who monster than a sign of environmental wellness, but the point of this research was to see if the mussels did in fact prosper in this environment, as it could have implications for how to help clean up coastal waters in various parts of the world.
The project was a joint effort from NOAA and the Long Island Sound Study, who aimed to see whether certain types of mussels could help to rid coastal waters of the damage done by sewage, fertilizers, and other pollutants. These nasty things in coastal waters have generated what Greenberg calls ‘an onerous influx of nitrogen’ which can ‘deprive coastal waters of oxygen when the algae die and decompose.’ According to Gary Wikfors, an aquaculture expert and chief of the biotechnology branch at NOAA’s laboratory in Milford, Connecticut, ‘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.’
Mussels work in three dimensions, thanks to their long tendrils of bivalves. This means they can work throughout the water column at incredible densities. Carter Newell, the founder of Pemaquid Mussel Farms in Damariscotta, Maine, who was on the Bronx River raft with Greenberg, explains, ‘My mussel rafts are 40 feet by 40 feet. That means they can filter something like five million litres of water per hour.’ As well as providing some speedy, top-notch filtration, mussel rafts also provide habitat. Newell, who has a PhD in marine biology, notes, ‘I have counted 37 different species of invertebrates living among the mussels on their culture ropes.’
On top of this, as bivalves go, mussels are perhaps the easiest to grow, thanks to a tremendous amount of wild mussel seed – or spat – still swimming around in American waters. Bren Smith, owner of the Thimble Island Oyster Company in Connecticut, comments, ‘I first got the idea to grow mussels after Hurricane Irene. After Irene there was just this incredible abundance of mussel larvae in the water and they set everywhere. Lobstermen were complaining that their traps were full of mussels. I realised all I’d have to do was provide the structure and I could have a mussel farm.’ He adds, ‘Irene completely buried my oysters and killed them. [Hurricane] Sandy did, too. The mussels — they were just hanging there on the ropes. They did fine.’
It’s not just individual mussels that are in abundance; there’s also a great deal of mussel saltwater mussel species, which means that mussels are adaptable to a wide range of conditions. Eva Galimany, a marine biologist with the Institute of Sciences of the Sea in Barcelona and a member of the team working on the NOAA project in New York, says, ‘From my experiments, they are great survivors, barely get sick, and can cope with many types of weather issues and toxins.’ However, Thierry Chopin, a marine biologist at the University of New Brunswick, has found an even better source of natural water filtration; seaweeds.
Not only has he found seaweeds to absorb persistent inorganic nutrients in the water column much more effectively than mussels, but unlike bivalves – which use oxygen as they filter and respire – photosynthetic seaweeds generate oxygen, which creates a more oxygen-rich system. He points out, ‘The big problem is that if mussels filter phytoplankton and organic matter they also ingest all that comes with it, and that can be elements or chemicals that reach toxic levels. What do you do with these mussels? Dump them somewhere? Then you create a pile of toxic material somewhere else.’