Just off the shore in Casco Bay, Maine, marine scientist Scott Lindell descends into an underwater kelp forest, his ears filling with frigid water as he swims down to the seafloor. Lindell’s mission: to find sugar kelp, a golden-brown, frilly-edged seaweed—and, more specifically, sugar kelp in its reproductive phase. Peering through his mask in the swirling, murky water, Lindell can only see a few feet, so it’s not an easy task.
What he’s looking for: kelp blades streaked with sorus tissue, a dark band teeming with millions of spores. A wiry man in his 60s, Lindell has developed relationships with homeowners and researchers across hundreds of miles of New England’s coast so he can access the kelp integral to his work—and, potentially, to the future of seaweed farming in the United States.
After several dives, Lindell has filled his mesh collection bag with cuttings and swims to shore. He stores the prized tissue in a cooler to keep it damp and cool for the five-hour drive, and then sets off for his laboratory at Woods Hole Oceanographic Institution in Massachusetts. Here, over the next 45 days, the spores will be carefully cultivated into seed for farmers and scientists to outplant in the ocean.
Every year, every ounce of any kelp variety farmed commercially in the U.S.—now approaching millions of tons—begins with this process. Many growers see it as a bottleneck: Propagation from wild-harvested seaweed is costly, lengthy, and ties rural coastal communities to laboratories that are often hours, if not days, away. It also shortens the seaweed growing season, as sorus tissue can only be harvested for a few months of the year. And, most frustrating to farmers, relying on wild stocks for farmed kelp means that growers have very little control over the final product. What could look underwater like a yummy blade may turn out to be a varietal better suited to feeding snails than pleasing the human palate.
Lindell’s eponymous lab at Woods Hole may look humble, with low ceilings and cement floors, but it’s meticulously organized, with hundreds of seaweed varietals catalogued and floating in refrigerated containers. As ferry horns punctuate the rushing sound of seawater piped into scores of tanks, a team of scientists toils away at an ambitious project: revolutionizing kelp propagation. They have just mapped a single sugar kelp genome for the first time, and the results are about to be publicized through the Joint Genome Institute in Berkeley, California. Next, they plan to map a genome for the entire species. The project is supported by a $5.9 million grant from the U.S. Department of Energy MARINER program, part of more than $66 million that the agency has invested in American seaweed production since 2018.
If successful, their work will put Americans at the front of seaweed science globally, making it possible for laboratories like theirs to select wild kelp with ideal traits and create new kelp “seeds” in two weeks. This breakthrough in selective breeding would be the biggest advance in mariculture in the past hundred years, akin to Punnett’s Square, which revolutionized plant breeding in the early 1900s.
A Keystone Species in Decline
The largest vegetative biome in the world, kelp supports the bottom of the marine food chain, nourishing species like snails and lobsters. Humpback whales play with floating kelp, while sea otters wrap themselves in its wide brown blades. Some kelp can stretch as tall as a 15-story building, with fronds that dance in the ocean’s currents, creating an underwater habitat for species as varied as otters, sharks, and octopus. These underwater forests cover a third of the world’s coastlines, providing a buffer for terrestrial species as well by protecting coastlines from the full impact of hurricanes and monsoons.
Different varieties of kelp have thrived in the world’s oceans for more than 100 million years, along the equator and up toward the poles. In 2023, scientists estimated that kelp forests suck up about a third of the world’s atmospheric carbon; kelp also supports fisheries and removes nitrogen pollution. Together, these benefits are valued at as much as $500 billion annually.
Now, this complex, ancient species is in jeopardy. Globally, kelp forests are receding at a rate of 1.8 percent a year, due in part to climate change and human impact. In 15 years, marine scientists say there may not be enough wild stock for farmers to rely on, especially in states like Maine, where kelp forests are rapidly declining. On the West Coast, kelp loss has been even more extreme, with 96 percent of forests from San Francisco to northern Oregon dying off over the past decade, according to The Nature Conservancy. Beginning in 2013, a series of cascading events wreaked havoc: First, a massive heat wave plunged the kelp into stressed conditions at the same time that purple sea urchins—which feed on kelp—lost their biggest predator, the sunflower sea star. Without sea stars to keep them in check, the urchins multiplied and, in a behavioral shift, left their customary nooks and crannies and began devouring the kelp forests.
Scientists believe Lindell’s work could help save the future of seaweed. By mapping sugar kelp, Lindell is creating a Rosetta Stone of kelp traits and corresponding DNA that can then be used by researchers globally to better understand, and protect, their wild kelp populations.
“We can’t go and remediate 350 kilometers of coastline, but we can certainly create oases along the way.”
For example, for a kelp forest stressed by increasingly warmer waters, conservationists could identify and plant strains of kelp that are more heat tolerant. Tristin Anoush McHugh, kelp project director at The Nature Conservancy, monitors California’s remaining forests regularly, and believes that Lindell’s advances in seaweed reproductive technology could bolster restoration efforts. Scientists could isolate kelp that survive mass die-off events, propagate them in the lab, and then plant them in the open ocean, creating kelp refuges. “We can’t go and remediate 350 kilometers of coastline, but we can certainly create oases along the way,” she says.
A Market Worth Millions
If kelp forests disappear, so would wild-harvested seed for farmed kelp. Investment in American-grown seaweed—roughly $380 million to date from the U.S. government, venture capital, and private investors—would have been for naught. Lindell’s work could benefit U.S. kelp farming by helping restore wild seaweeds—but also through reducing costs.
For decades, China has led the industry, valued at $643.4 million in 2022, a slice of the larger $5.6 billion global seaweed market. According to the U.N.’s Food and Agriculture Organization, China produces 89 percent of the world’s farmed kelp; the U.S. produces less than .01 percent—what one hatchery specialist in Maine calls a “rounding error.”
“I don’t know any other agricultural or aquaculture industry where the cost of seed can be as much as 50 percent of the farmer’s revenue.”
Many kelp companies in the U.S. cite America’s small appetite for seaweed as an impediment, especially compared to Asia, where seaweed is consumed regularly and in many forms. But minimal demand is only one reason for the low market share. The high cost of farming is another.