Got Seaweed?  Could kelp help New England's declining seafood industry, climate change


For Granite State News Collaborative

Published: 07-17-2023 12:00 PM

RYE –Along the shores at Odiorne State Park, sparkling tide pools and gray boulders provide the perfect environment for Gabby Bradt, a marine biologist and fisheries specialist at the New Hampshire Sea Grant, to forage for yellow-green tendrils of Rockweed, a seaweed also known as Bladderwrack.

Since 2015 Bradt has led New Hampshire Sea Grant’s “Seaweed Mania” Spring workshops, teaching individuals how to harvest and prepare seaweed in her quest to open people’s minds to the plant’s potential.

Bradt is a key player in efforts by the New Hampshire Sea Grant to expand the public’s understanding of the roles seaweed can play in our lives, as seafood production declines due to climate change.

“Part of what I have been doing is trying to teach people that seafood and seaweed, it’s not scary,” Bradt said. “The other aspect of it is going out in the field and learning to identify the, you know, 10, edible seaweeds that you can find on the coast of New England or New Hampshire, and sort of teaching them how to forage sustainably and all the rules and regulations that go with it.”

New Hampshire law allows an individual to harvest up to three bushels of seaweed for personal use every day, according to New Hampshire Sea Grant. However, Bradt’s classes emphasize sustainability. Individuals are not recommended to harvest a whole three bushels (almost 28 gallons) unnecessarily, nor should they harvest from one site, which could disturb the environment.

Although the commercial seafood industry is a small portion of New Hampshire’s economy, it still brings in an estimated $700 million in yearly revenue which supports about 5,000 full and part-time jobs, according to 2020 data from the Department of Commerce.

For neighbors like Massachusetts and Maine, commercial fishing holds even greater importance. The industry supports almost 37,000 jobs in Maine, and over 127,000 jobs in Massachusetts.

However, the robust seafood industry’s future is threatened by rising sea temperatures as some species migrate north in search of cooler, less acidic waters.

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A 2023 report from the National Marine Fisheries Service indicates that 2022 was the warmest year on record for the North Atlantic. As water temperatures increase, oceans store more carbon dioxide which in turn increases their acidity. This process can spell disaster for sea life, causing a number of harmful health defects to shellfish and fin-fish.

In 2019 the U.S. Department of Commerce reported noticeable declines in New England seafood harvest. Commercial fishermen harvested over 516.7 million pounds of fish in 2019, a 15% decrease from 2010 and a 13% decrease from 2018.

Recently, the industry has seen the largest decreases in catches of Atlantic herring, Atlantic Mackerel and the American Lobster. Northern shrimp populations have plummeted so sharply that fishing them has been prohibited since 2014.

In the face of this threat, the scientific and marine community is looking to seaweed as a partial solution for the future because of its sustainability and unique role in ocean ecosystems.

“One of the great things about growing kelp, unlike almost every other crop that we have, is that they don’t require any (additional) water,” said Thew Suskiewicz seaweed supply and innovation manager at Atlantic Seafarms, Maine’s largest seaweed company.

“They don’t require added nutrients or fertilizers and we don’t use pesticides on them. So, from an input standpoint, and from an energy standpoint, they’re about as efficient as you can get.”

He also explained that seaweed farms can reduce the impacts of ocean acidification by creating a “zone” of low acidity in the places where the seaweed is growing. Through the process of photosynthesis, seaweed takes up carbon, lowering the acidity of the surrounding water. The macroalgae also take up nitrogen and phosphorus, which can contribute to excessive algae blooms and ocean acidification.

These properties of seaweed make their surrounding environment more hospitable for shellfish such as mussels, oysters, crabs and lobster.

Seaweed is easily mistaken for a plant, but it is actually a type of microalgae — a type of living organism that is classified separately from plants because of its lack of leaves, roots or stem. Kelp, often used interchangeably with seaweed, is the subspecies of seaweed most popularly grown in the Northeast.

“Kelp encompasses a bunch of different types of brown macroalgae, so the most common that’s being grown right now is sugar kelp,” Bradt said.

For New England fishermen slowly watching their annual catch decline due to the impacts of climate change, seaweed is a promising venture. Many of the farmers with Atlantic Sea farms grow seaweed to supplement their income from lobstering or fishing.

“They’re seeing this as something that they can do when they’re not lobstering in the offseason, that will continue to earn them money, continue to keep their crew…employed,” said Suskiewicz. “And allow them to use all of the skills and equipment they already have.”

No easy task

However, harvesting seaweed is a challenging enterprise, as Kittery-based kelp farmers Inga Potter and Krista Rosen can attest.

One sunny Friday morning in May, Potter and Rosen, owners of Cold Current Kelp, traveled to Pepperrell Cove for their second kelp harvest of the spring season. In a few weeks, they need their lines to be completely removed to make room for summer activities on the water. Geared up in rubber gloves and bright orange fishing overalls, the two remove kelp off the lines by hand, hauling rope up from the water and carefully using a machete to slice it off. Then, they pack it piece-by-piece in storage containers. Working against the wind and the beating sun, the process can take hours.

“[Harvesting] it’s very labor intensive if you’re doing it piece by piece. There really doesn’t exist yet in Maine a really fast and efficient way of drying kelp,” Rosen said.

Potter and Rosen manage all of their processing alone. They put out the seed line in the fall, which grows throughout the winter. Then the kelp is harvested in the Spring and brought to a rented greenhouse for drying, which takes a few days.

Rosen described the process as highly weather dependent, as the greenhouse must be dry or the kelp will absorb any moisture in the air.

Potter and Rosen will offer the harvest to Maine customers primarily for use in beauty and skincare. They cited seaweed’s sustainability and its potential for local impact as their main motivations for founding Cold Current Kelp.

“It feels good to be growing something that can impact the marine environment and potentially have effects on a global scale,” Rosen said.

Obstacles to growth

Commercial development of seaweed aquaculture in New England only began around 2010, and the industry is fairly young compared to the Asian market. As a result, regulatory infrastructure and processing facilities are not yet available in the capacity farmers need.

In Maine, a surge in aquaculture interest during the past decade quickly outpaced the state’s capacity to lease permits. It is now estimated there are more than 140 farms in the state. The rapid evolution of the industry also means regulations can quickly become out of date.

“The experimental and the standard leases, I think, typically take two or three years,” said Rosen. “And so that is an issue you hear in the aquaculture community, quite frequently, that the process could be a little faster.”

Another obstacle for potential growers is the up-front costs of seaweed farming, which can be steep for those without fishing or lobstering gear. Currently, Potter and Rosen borrow a boat to plant and harvest, as owning one would be too expensive.

Nonprofits expanding climate-friendly fishing practices, such as Greenwave, hold one piece of the puzzle. Their Kelp Climate Fund provides subsidies to ocean farmers committed to engaging in seaweed aquaculture, facilitating the transition process.

New Hampshire’s role

Against a backdrop of an expanding seaweed industry along New England’s coast, Bradt expects that New Hampshire’s main contributions will continue to be through research and consumer demand.

“I don’t think in New Hampshire, there is really any real potential…maybe very small scale,” she said. “But not a lot that would bring in a lot of jobs or anything like that.”

Key challenges include limited coastline and the lack of infrastructure. Lobstering and fishing leave less room for aquaculture on New Hampshire’s shorter coastline.

“We have such a short coastline,” said Bradt. “It’s pretty rocky access to where you would want to go… you wouldn’t be able to grow enough to meet any sort of demand.”

She suggested multi-trophic aquaculture (a farming system in which multiple organisms are grown together) might hold greater potential as a role for seaweed in New Hampshire. Oyster aquaculture has rapidly expanded in Great and Little Bay, and research is revealing the benefits of growing seaweed in combination with shellfish.

Suskiewicz said that at Atlantic Sea Farms, farmers are already doing this.

“Over the last couple of years, [shellfish growers have] actually come to us and said, ‘hey, when we put kelp lines around our mussel wraps, when we put kelp lines around our oyster cages, our oysters and mussels do better,’” said Suskiewicz.

No ‘magic bullet’

In terms of climate change solutions, Bradt cautioned that seaweed should not be lauded as a “magic bullet” just yet. While seaweed has positive impacts locally, just how beneficial it would be on a larger scale is unknown.

“It is really exciting… but we haven’t tested it enough. We haven’t scaled it up enough to be able to do that,” she said.

She also noted that once growers try to expand past the local level, sustainability starts to become complicated. For example, seaweed products from the coast become less sustainable once they’re shipped to the middle of the country.

“I think that’s where things start to sort of fall apart, is trying to grow, and of course, everybody wants to grow,” Bradt said.

Scientists hope that seaweed can help with the process of carbon sequestration, a method of reducing carbon dioxide in the atmosphere by capturing and containing it, either through living organisms or land formations. A common example of this effort is the planting of more trees to ‘save the planet’.

However, seaweed is only storing carbon through photosynthesis as long as it remains unharvested or alive.

“If you think about it, all right, fine, you have all these seaweed farms. And yes, they are sequestering carbon and so on and so forth,” she said. “But they’re not going to live forever.”

Once seaweed decomposes or is consumed by another organism, the carbon it was storing will find its way back into the environment. The lifespan of seaweeds varies, with some growing annually and others having lifespans as long as ten years.

Suskiewicz agreed that Kelp alone cannot “cure” our coastal environments of acidification but added that seaweed is still a preferable food source because of its minimal impact on the environment.

“For every calorie or pound of food that someone’s consuming kelp, it’s much less input than it is for almost anything else,” he said.

Is the Northeast “sold” on seaweed?

Whether it’s a kelp beer in Portsmouth or a seaweed salad while fine dining, many local businesses have embraced the macroalgae as they look toward a more sustainable future.

Evan Henessy, a Dover chef who runs fine dining restaurant Stages at One Washington, prides himself on using local and sustainably sourced seafood. He describes seaweed as a highly versatile source for a savory “umami” flavor, which can be used to create anything from dashi, a Japanese soup broth, to a paste for salad dressing.

“That’s only a few possibilities in the culinary world,” he added. “But these are a lot of systems, a lot of work and a lot of people that need to be involved in creating this change.”

Market outlets for seaweed

Currently, seaweed has several market applications.

Raw seaweed can be dried or frozen and served as a meal ingredient. It can also be added to commercial food products such as vegetarian burgers, condiments, and seasonings. On its own, it can be fermented or pickled for sale.

Seaweed is also used in many personal care products including face creams, face oils, face masks, shampoos, conditioners, soaps, and lotions.

In addition, seaweed can be found in health supplements and even fertilizer.

Henessy and Bradt emphasized marketing issues for a lack of significant demand in seaweed products. They also noted the lack of value-added products on the market.

While research has shown uses for seaweed in everything from animal feed and biomass fuels to compostable plastic, many of these products have yet to reach the commercial stage. A lack of variety in commercial seaweeds also limits potential consumer interest. If a consumer has a variety of options, they are more likely to find a seaweed product or food they enjoy.

“I think that does limit people’s interest in it,” Bradt said. “That’s one area of research that people are trying to grow… what else can we grow at a commercial scale or more easily?”

At the University of New Hampshire, Professor Chris Neefus has been researching the optimal methods for commercial Nori production, the seaweed mainly used for sushi.

To grow new varieties of seaweed, researchers must determine the most conducive environment for growth, or how to replicate their natural environment. Different varieties of seaweed also have different life cycles, and may grow differently. While kelp can be grown off of seeded rope lines, other seaweeds might fare better in a lab tank.

“So it’s not as straightforward as being like I’m just gonna plant carrots and peas and you know, radishes all on different rows on the same plot of land,” Bradt said. “It’s a lot more complicated.”

As a specialist in commercial fisheries, Bradt spends a lot of time thinking about how to sell sustainable products like seaweed.

“I do really want to figure out how to hit that right messaging for marketing seaweed,” she said. “Other industries have had, you know, the success of kale, ‘got milk’… what about that resonated so much that demand and market share increased?”

Bradt’s hope is that over time the relationship between growers and markets will balance.

“One of the things I’m working on with the Sea Grant seaweed hub is exactly trying to figure that out,” she said. “How do we expand those markets?”

She points to her daughter’s experiences with seaweed for a sense of what the future could be.

“She never knew that it was gross and slimy,” said Bradt. “I always taught her ‘look, Rockweed, over here, pop this bubble, and now you have smooth skin.’ But at the same time, ‘clip the top over here, and it tastes like nuts. If you’re hungry, there’s a snack.’ She’s been doing that her entire life.”

Bradt sees educational efforts, like her work at the NH Sea Grant, as key to mobilizing the younger generation of entrepreneurs and consumers to utilize seaweed to its full potential.

“Seaweed really, absolutely, has the potential to save the world,” Bradt said. “If we do it right.”

Amanda Pirani is a New Hampshire native and previously studied at the University of New Hampshire, where she reported on seaweed for an advanced reporting course on Climate Change. She plans to continue her degree in political science as a rising junior at the University of Michigan.These articles are being shared by partners in The Granite State News Collaborative. For more information visit]]>