Sound Facts

Sugar Kelp

Winter is Sugar Kelp Season!

Dr. Yarish, with a student, holding a kelp plant over 20 feet long at the UCONN Stamford campus. Photo (from 2016) courtesy of Charles Yarish/UConn.

Sugar Kelp, Saccharina latissima, is a brown-colored seaweed that thrives in cold waters in Long Island Sound and other areas of the northeast. Aquaculture farmers seed juvenile kelp on long lines attached to buoys or docks in November and December, and then wait until spring to harvest the fast growing kelp crop. Dr. Charles Yarish, an emeritus professor at the University of Connecticut, said that farm-cultured kelp he has harvested for research in Long Island Sound has grown to as long as 8 meters (26.2 feet). Wild kelp also grows naturally to as long as seven meters (23 feet) in Long Island Sound.

Dr. Yarish noted that in the 1980s he had harvested kelp that grew to as much as 12 meters (39.4 feet), but over the past couple of decades the growing season has shortened as Long Island Sound waters have gotten warmer.

Back in 2012: Jang K. Kim (right) , formerly an Assistant Research Professor at UConn, and Jen Savicky (left), a former undergraduate student at UConn, harvest kelp at the Thimble Island Oyster Farm off Branford in early spring. Kim and Savicky were part of a research project led by Dr. Yarish to test whether nutrient-rich seaweed such as kelp can be grown and harvested in the Sound to improve water quality by extracting nitrogen, while also providing food, biofuel, and other commercial products. Oyster farmer Bren Smith was a partner in the research project. At the time of outplanting in November 2012, the plants were about 1mm in size, and grew to lengths of 6 meters.

Nine years ago, a UCONN research team funded by LISS and led by Dr. Yarish investigated whether kelp can be used in the Sound to help improve water quality by reducing nutrient pollution. Kelp needs nutrients such as nitrogen to grow, but nitrogen also fuels the growth of microscopic algae, which in excess can lead to a severe drop in oxygen levels in coastal waters. In turn, severely depleted oxygen levels can harm wildlife, including inducing massive fish kills. At three farm sites in the nearshore waters off the Thimble Islands (Branford, CT), Bridgeport and Fairfield, CT, and at the mouth of the Bronx River, Yarish’s research team demonstrated that a significant amount of nitrogen is removed from the Sound when aquacultured kelp is harvested.

In recent years, LISS has continued to support these and other pilot projects—known as nutrient bioextraction—on Long Island, in the Bronx, and in the Greenwich/Stamford areas of Connecticut. You can learn about these projects in the nutrient bioextraction section of the LISS website.

Dr. Aaren Freeman, a marine scientist at Adelphi University (right), and Adelphi students Amanda Hornung and Thierno Diallo pose for a picture after a day of seeding long lines with juvenile kelp seed. Photo courtesy of Dave Gugerty.
Dr. Aaren Freeman, a marine scientist at Adelphi University (right), and Adelphi students Amanda Hornung and Thierno Diallo pose for a picture after a day of seeding long lines with juvenile kelp seed in winter 2019. Photo courtesy of Dave Gugerty.

Besides the ecological benefits, kelp has many potential economic benefits as well, although it remains a challenge to develop markets for the kelp as a crop. Kelp is an excellent dietary source of fiber, vitamin C, vitamin K, iron, calcium, magnesium, iodine, and other trace minerals; it can be used dried, powdered, fresh, cooked, and fresh frozen (source: CT Department of Aquaculture). In New York, where kelp is not yet permitted to be harvested for food, pilot projects are looking at alternative uses, including extracting kelp for fertilizer. Dr. Yarish is also part of national research projects with the US Department of Energy developing a selective breeding program and scalable aquaculture of sugar kelp as well as looking into the viability of using kelp biomass as a biofuel and in other applications for food and feeds. With another one of his former post-doctoral students, Dr. Schery Umanzor, Dr. Yarish is looking at the capacity of nutrient bioextraction by kelp farms at farms in the Northeast and the Pacific Northwest of the US.

Learn More:
Bren Smith and other kelp growers were recently interviewed in a New York Times article on the challenges of growing sugar kelp for the American marketplace.

Shellfish can also be used for nutrient bioextraction as this graphic shows. Learn more in the nutrient bioextraction section of the Long Island Sound Study website.

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