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Kelp Farming May Help Clean Polluted Waterways and Fight Climate Change

Though too toxic to eat, the seaweed in Newtown Creek, Gowanus Bay and the East River could suck up carbon and pollutants, bolstering marine ecosystems.

March 23, 2023 Samantha Maldonado, The City
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Paddling their boat in a creek inlet in Greenpoint, Shanjana Mahmud and Luke Eddins, volunteers with the Newtown Creek Alliance, headed to a series of yellow buoys.

Against a background of the piles of metal at a recycling facility and the Long Island Expressway on Friday, Mahmud reached into the water and lifted a rope tied to a buoy. The line emerged dripping with the shaggy spirals of a rubbery brown seaweed: sugar kelp.

Kelp can be tasty in salads, when dried into chips or used for seasoning, but what’s growing in Newtown Creek — a toxic Superfund site sandwiched between Brooklyn and Queens — is not for eating.

Instead, the kelp is an experiment.

“Will it grow in this place where it has low salinity because there’s more combined sewage overflows?” said Mahmud, who is leading the project. “Even in these conditions, we’re seeing growth everywhere.”

At Newtown Creek and elsewhere around the polluted waters of New York City, people are growing kelp and studying how it could offer local environmental benefits and even help fight climate change.

“Seaweed is a small part of a solution to a very big problem,” said Michael Doall, the associate director for shellfish restoration at Stony Brook University’s School of Marine and Atmospheric Sciences, who is growing kelp in the East River, in the shadow of the Throgs Neck Bridge.

Kelp hangs from a rope tethered to a buoy near the Throgs Neck Bridge.
Stony Brook University researcher Michael Doall has been growing kelp near the Throgs Neck Bridge in the northern reaches of the East River. | Courtesy of Michael Doall

“Can you actually do anything to improve water quality? Or is the scale that you would need to improve water quality even feasible? How much kelp do we need to grow to actually tip the balance in New York Harbor? That to me right now is a research question,” Doall said.

Having been used for commercial purposes since the 1800s, Newtown Creek became toxic thanks to the raw sewage, waste and chemicals dumped in the water from the nearby combined sewers, oil refineries, fertilizer factories, lumber yards and other heavy industrial uses. Over more than a century, oil companies spilled tens of millions of gallons of oil into the soils and aquifers in Greenpoint.

The state is working to remediate the site. The Environmental Protection Agency, which in 2010 included the creek on the Superfund National Priorities List, is expected to complete the development of its creek cleanup plan by 2028, and will begin the actual cleanup process as early as 2032.

‘Citizen Science’

Kelp could improve water quality and restore marine ecosystems by sucking up carbon, nitrogen and phosphorus from runoff and the raw sewage that flows into the water from the city’s sewer system when it rains. The nitrogen and phosphorus can cause “harmful algal blooms” (HABs) and stifle marine life. Kelp can also absorb heavy metals and other toxins in the marine environment.

That kelp grows large and fast — up to 12 feet long in five months — means it could be especially effective, as does its propensity to thrive in cold climates like New York’s, Doall said. Plus, there’s evidence that kelp can lower ocean acidity, and thus enhance shellfish growth.

In coastal New England, oyster farmers have incorporated kelp into their businesses as a winter crop. Commercial kelp farming is limited in New York, however.

Luke Eddins paddles through Newtown Creek while checking kelp ahead of harvest season, March 17, 2023.
Luke Eddins paddles through Newtown Creek while checking kelp ahead of harvest season, March 17, 2023. | Hiram Alejandro Durán/THE CITY

The state Department of Environmental Conservation issues permits to allow kelp cultivation in public waters, and the Department of Agriculture and Markets regulates the distribution and use of the harvest. Entities that want to sell seaweed as a food must apply for a license.

As a way to boost the fishing economy and promote marine restoration, Gov. Kathy Hochul in 2021 signed into law a bill for Suffolk County to lease underwater lands for commercial kelp farming. The following year, citing a need for the Suffolk “pilot program” to be assessed, Hochul vetoed a bill that would have expanded where kelp could be farmed.

Still, growing kelp for ecological purposes — akin to what THE CITY reported about oysters in December — instead of commercial ones is somewhat new territory.

“No one is growing a commercial species in a Superfund site — that’s nuts,” said Nick Russell, a researcher with the Newtown Creek Alliance and a student of environmental sciences at Queens College. “It’s really about using an organism that used to be native to this area in an impacted urban waterway for remediation. … The point is creating sort of a pilot for community involvement and citizen science.”

As part of his studies, Russell is working to identify and count the heavy metals absorbed by the kelp that Mahmud and Eddins are growing as a means to understand what’s in the water.

Justin Realmuto takes a look at the kelp growing in the water off Red Hook.
Justin Realmuto takes a look at the kelp growing in the water off Red Hook, March 19, 2023. | Samantha Maldonado/THE CITY

Elsewhere in Brooklyn, volunteers at the RETI Center are growing kelp in the Gowanus Bay, near the IKEA store in Red Hook. They’re testing how lines of kelp fare in varying depths of water, and in an area where the tides often knock the lines out of place.

Justin Realmuto, a volunteer, said when it’s time to harvest the kelp in May, the center will explore possibly using it for biofuel, as an additive to concrete, or to make bioplastic — all emerging technologies.

“It’s this amazing thing that almost grows by itself,” Realmuto said, “but it’s nowhere near edible, and also so toxic that there’s very little we can do with it.”

What’s in the kelp may determine how it can be used. Contamination may limit kelp’s potential as a fertilizer, for instance.

That’s something Doall is hoping to find out. In addition to measuring the water quality around the kelp he’s growing and the level of contaminants in the kelp, he plans to grow some spinach, carrots and tomatoes, fertilize them with kelp, and track whether the contaminants seep into the soil and vegetables themselves.

Connecting to Nature

In May, the volunteers at Newtown Creek plan to harvest only a portion of the kelp, leaving some in place on each line to see what happens to it, as the water warms through the summer. New York City is about the southernmost limit of where sugar kelp can thrive.

If the kelp withstands the climbing temperatures, Mahmud said she’s curious if the kelp will act as a reef for other organisms to make a home on or near it.

“If this tiny effort can, for a little bit, create an ecosystem for something, for some life, that’s great,” she said.

Kelp is hung up to dry in the greenhouse at the Southampton campus of Stony Brook University.
Sugar kelp is hung to dry in the greenhouse at the Southampton campus of Stony Brook University. | Courtesy of Michael Doall

Mahmud sees potential for kelp to connect New Yorkers to the water surrounding them and make them more aware of the living environment.

This was apparent to her last spring. When the team harvested the kelp and hung it to dry, Mahmud noticed speckles of barnacle larvae on the leaves and how the salty scent of the sea filled the air.

“It was kind of this immediate reminder that this neglected waterway is still part of the earth,” she said. “It’s a very sensory experience to be like, ‘Oh, that’s not just trash. It’s the ocean.’”

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