Seaweed Farms May Ease Ocean Acidity, Improve Water Quality
Research - News

Photo caption: Cultivated Gracilaria tikvahiae is suspended from a rope in Long Island Sound. Credit: Christopher Gobler, Stony Brook University

By Chris Gonzales, Freelance Science Writer, New York Sea Grant

Stony Brook, NY, September 14, 2022 - Scientists are growing multiple types of seaweed in Long Island Sound, in near-shore locations in Connecticut and New York. Their goal: improve water quality while expanding the industry for cultivated seaweed, oysters, and mussels in the region.

The species they’re growing include the cold-water Saccharina latissima and the warm-water Gracilaria tikvahiae and Ulva.

As they do so, they’re measuring nitrogen and carbon removal rates. In addition, they’re measuring and mapping changes in water quality, including dissolved oxygen, acidity levels, and harmful algae concentrations.

Christopher Gobler, an ecologist at the School of Marine and Atmospheric Sciences at Stony Brook University, is leading the research team, with funding from New York Sea Grant.

When the project is complete, they’ll share their results with other aquaculturists and the public—publishing a guidance document and hosting a workshop detailing best practices.

Unknown benefits

It’s become increasingly popular to farm kelp (Saccharina latissima) in Connecticut and New York. But the ability of this particular species of kelp to filter nitrogen is limited to the cold-weather months. Warm water seaweeds, though, Gracilaria and Ulva species, could compliment kelp in the warmer months. However, little is yet known about the ability of warm water seaweeds to benefit bivalves such as oysters and mussels.

Scientists are seeking to learn more about co-cultivating Gracilaria with bivalves. They expect it will improve water quality—specifically, sequestering nitrogen and carbon, increasing dissolved oxygen, pH, and alkalinity. But will mussels and oysters grown in this environment grow faster, be healthier by a range of standards, and have higher settlement and survival rates—key measures of reproductive ability?

Temporary nitrogen remover

During the past 15 years, multiple species of new harmful algal blooms (HABs) have emerged in coastal Long Island Sound waters. These have been shown to have been promoted by excessive nitrogen.

The largest source of nitrogen is residential septic systems. While significant efforts are underway to upgrade these septic systems (some 400,000 of them) interim measures are needed to remediate water quality.

Cultivated seaweed—specifically, Gracilaria—holds promise as a way to remove nitrogen from the water and generally improve water quality until broader efforts to reduce nitrogen loading into the Sound have their full effect.

Gracilaria can be harvested as a crop for food or fertilizer, thus removing the nitrogen from specific sites in the ecosystem.

There are many examples of Gracilaria grown experimentally in NY, including by GreenWave's Thimble Island Farm in LIS, the Gobler Laboratory, and the Stony Brook-Southampton Marine Lab.

Since this species of seaweed can be grown in the warmer months, when need is greatest, because HABs risk is high, they could potentially help the most.

A further benefit of the research: farmed seaweed could boost the crop of oysters and mussels, a profitable crop and food source.

The research project began in spring 2022 and is expected to be completed in early 2024.

More Info: New York Sea Grant

New York Sea Grant (NYSG), a cooperative program of Cornell University and the State University of New York (SUNY), is one of 34 university-based programs under the National Oceanic and Atmospheric Administration’s National Sea Grant College Program.

Since 1971, NYSG has represented a statewide network of integrated research, education and extension services promoting coastal community economic vitality, environmental sustainability and citizen awareness and understanding about the State’s marine and Great Lakes resources.

Through NYSG’s efforts, the combined talents of university scientists and extension specialists help develop and transfer science-based information to many coastal user groups—businesses and industries, federal, state and local government decision-makers and agency managers, educators, the media and the interested public.

The program maintains Great Lakes offices at Cornell University, SUNY Buffalo, SUNY Oswego and the Wayne County Cooperative Extension office in Newark. In the State's marine waters, NYSG has offices at Stony Brook University in Long Island, Brooklyn College and Cornell Cooperative Extension in NYC and Kingston in the Hudson Valley.

For updates on Sea Grant activities: has RSS, Facebook, Twitter, Instagram, and YouTube links. NYSG offers a free e-list sign up via for its flagship publication, NY Coastlines/Currents, which is published quarterly.

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