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.
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“My mussel rafts are 40 feet by 40 feet,” Newell told me. “That means they can filter something like 5 million liters [1.3 million gallons] of water per hour.” Mussel rafts also provide habitat, something oyster reefs once did when they were bigger and more substantial. “I have counted 37 different species of invertebrates living among the mussels on their culture ropes,” said Newell, who has a Ph.D. in marine biology.
Mussels are also perhaps the easiest bivalve to grow. This is due to the tremendous amount of wild mussel seed, or “spat,” that still swims in American waters. Back when wild oysters were abundant, waterways were dense with oyster spat. But following the oyster’s collapse, oyster spat is increasingly rare.
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“I first got the idea to grow mussels after Hurricane Irene,” Bren Smith, owner of the Thimble Island Oyster Company in Connecticut, told me recently. “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 realized all I’d have to do was provide the structure and I could have a mussel farm.”
The effects of Irene and other storms also highlight the mussel’s inherent hardiness. “Irene completely buried my oysters and killed them,” Smith told me.
“[Hurricane] Sandy did, too. The mussels — they were just hanging there on the ropes. They did fine.”
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, noted the sheer abundance of saltwater mussel species (many more than oysters and distributed in intertidal zones throughout much of the world) means that mussels are adaptable to a wide range of conditions.
“From my experiments, they are great survivors, barely get sick, and can cope with many types of weather issues and toxins,” she said in an interview.
And since they can cope with difficult conditions it’s hoped that mussels could make it in places like the Bronx and theoretically be harvested and ground up for fish food, assuming they did not contain large quantities of toxics.
But some scientists believe there is only so much that mussels can do. A more diverse set of organisms, they maintain, will be needed to filter out the range of pollutants found in places like New York Harbor. For more than a decade, Thierry Chopin, a marine biologist at the University of New Brunswick, has been conducting research into the related field of “integrated multi-trophic aquaculture,” or IMTA, where salmon, mussels, sea cucumbers, sea urchins, and seaweeds are all cultured together. His research in the Bay of Fundy shows that blue mussels and kelp can be cultivated and thrive thanks, in part, to the wastes produced by nearby pens of farmed Atlantic salmon.
His research has also revealed that seaweeds absorb persistent inorganic nutrients in the water column much more effectively than mussels. And unlike bivalves, which use oxygen as they filter and respire, photosynthetic seaweeds generate oxygen, making for a more oxygen-rich system — provided they are harvested before they die and decompose.
Moreover, Chopin believes seaweeds can safely remove toxic substances.