“You’ve got to have a backup plan, especially now with climate change,” he said. “During the off-season, a lot of the guys work for other people, they do odd jobs, but I really want to stay on the water. Throughout the years, I’ve been urchining, I’ve been shrimping. But now that’s all done. So I figure I’ll try kelping.”

[Seaweed pods, anyone? Marathons are getting creative to limit their climate impact.]

In Stonington, Conn., Suzie Flores is farming three acres of kelp near the bait-and-tackle shop she owns with her husband. She sells it directly to chefs, and also at the local farmers’ market for $8 per half-pound bag. At home, she cooks with it regularly, chopping it into vegetarian tartare and adding it to pizza for her children.

“I even mix it into my dog’s food,” she said. “Everyone in the house is eating kelp.”

So far, the profits have been on the low side. But as she beats the learning curve, Ms. Flores feels confident that they will rise. And even if they didn’t, the feel-good aspects of kelp farming make up for the lack.

“Every time we go to harvest, I think about all of the carbon we sequestered, and how much cleaner the water is,” she said. “For me, the farm doesn’t need to make money. Knowing that I’m helping the environment is enough.”

Fresh-frozen kelp is available through Atlantic Sea Farms, atlanticseafarms.com; Mermaid’s Garden, Brooklyn, N.Y.; Harbor Fish Market, Portland, Me.; Lois’ Natural Marketplace, Portland and Scarborough, Me.; Cambridge Naturals, Cambridge, Mass.; Common Crow, Gloucester, Mass.; and Buffalo Mountain Food Coop and Cafe, Hardwick, Vt. It is also available unfrozen at the Stonington, Conn., farmers’ market.

Recipes: Roast Chicken With Crunchy Seaweed and Potatoes | Lemony Pasta With Kelp, Chile and Anchovies | Creamy White Bean and Seaweed Stew With Parmesan