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Changes to the Gowanus Canal, part of a major cleanup project in the notoriously polluted waterway, are resulting in loss of mussel habitat. But community intervention could increase the Atlantic ribbed mussel population, with promising implications for the Canal’s future.
Gary Francis had spent much of his life fishing, boating and diving in the vast blue waters of the Caribbean.
When he came to New York City, he was mystified. The city is surrounded by water, but access to it was incredibly limited. Largely closed off and isolated, the city’s water was unwelcoming, much of it bordered by barbed wire or “no trespassing” signs.
Eventually, he found a home paddleboarding in the most unlikely of places: the Gowanus Canal.
“Everybody loves to hate on the Gowanus Canal,” said Francis, who is now captain of the Gowanus Dredgers Canoe Club. “Even as abused as it is, it is still incredibly beautiful and full of life.”
One particularly important piece of life in the Canal: the Atlantic ribbed mussel, known for its ability to filter water. Francis has been crafting artificial habitats to encourage the growth of these mussels, whose previous spaces are being threatened by changes to the Canal’s structure.
The Gowanus Canal is a notoriously polluted body of water. In the 19th century, it boomed as a commercial hub and supported large numbers of factories and chemical plants. This industrialization, coupled with an ongoing sewage overflow issue, led to its designation as a federal Superfund site in 2010.
A Superfund site is an area that has been identified by the U.S. Environmental Protection Agency as especially contaminated and hazardous. The agency oversees the cleanup of these locations.
Before its industrialization, the Gowanus Canal was a thriving salt marsh ecosystem. Now, it has a more inhospitable reputation, known for the “black mayonnaise” tar-like sludge that sits 10 feet thick along the waterway’s bottom.
Despite massive amounts of pollution, resilient organisms such as the Atlantic ribbed mussel have learned to survive in the Canal, where a $1.6 billion cleanup effort that broke ground two years ago is underway.
The cleanup looks to dredge the Canal of its contaminated sediment layer, cap off the dredged areas to prevent recontamination and construct two new tanks to capture sewage and stormwater from overflowing into the waterway when it rains.
But structural changes from the Superfund project may put the mussel population at risk, local environmentalists say.
“I would almost argue we’ve seen less biodiversity because oddly, all those shorelines that were not safe and good for anything—those were the biodiversity hot spots,” said Jennifer Kepler, education manager of the Gowanus Canal Conservancy. “There were nooks and crannies and spaces for things to hide and sit and grow.”
Many of the Canal’s mussels lived on the wooden bulkheads that reinforced the banks before the Superfund cleanup began. But the EPA has started to replace those wooden bulkheads with stronger steel ones.
While steel bulkheads provide the Canal with greater reinforcement, the swap destroys the mussels’ previous habitats, as the smooth surface of steel is uninhabitable compared to the porous texture of wood.
Mussels are 103 times more likely to be found on wood than on steel, according to a report published in 2021 by the Gowanus Canal Conservancy.
Francis noticed this habitat decline as he was paddling on the Canal. An ornamental plasterer by trade, he decided to use his skills to design and create artificial mussel habitats to replace those lost during the cleanup work.
In partnership with the Gowanus Canal Conservancy, Francis and the Gowanus Dredgers Canoe Club welcome local high school students to come to the Canal, learn about its ecosystem and design mock mussel habitats out of clay, cardboard or tinfoil. Francis then takes the student-made designs and uses them as inspiration for the Canal-bound structures.
“I’ve made many samples and tests,”said Francis, who’s been workshopping these habitats for six years. “What matters most is placement—where it is in the tidal spectrum—texture, and moisture.”
Francis started installing test models in 2019 and has since been experimenting with a variety of materials and installation methods. The final habitat modules are mostly made of concrete, which offers ideal texture and longevity. The habitats sit on steel shelves hung from the bulkheads.
The Gowanus Dredgers Club estimates the Canal’s current mussel population to be 362,700. If Francis’ project is successful, it could have positive implications for the ecological health of the Canal. A strong mussel population has a number of benefits.
Mussels are powerful freshwater filters that convert raw materials—such as the sewage that overflows into the Canal—into fertilizer, according to Denise Mayer, curator of malacology at the New York State Museum. They also increase biodiversity, reinforce shorelines and are a keystone species of salt marsh environments.
“Salt marshes are one of the most productive ecosystems on the planet,” said Mayer. “They’re hugely impactful for combating things like climate change.”
Francis started installing his replacement habitats in March of this year. He has yet to see mussels set up shop—but biofilm, barnacles, worms and other signs of life have begun to accumulate in the structures.
He said mussels will take “a bit longer,” but he’s optimistic. The mussels spawn in late summer, and he believes this spawn will lead to mussel recruitment onto the habitats in the near future.
Kepler finds the mollusks a reason to feel hopeful.
“A lot of people think the Gowanus Canal is this broken place that’s the end of times,” she said. “Nature figures out how to heal and find its balance. If we could just help it along I think it would find its balance quite well.”
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