Kelp may help shellfish growth in acidified waters, SBU study says

Long Island’s burgeoning aquaculture industry may have more reasons than the prospect of increased revenue to add kelp to their oyster farms: A recent study by Stony Brook University found it can dramatically increase shellfish growth rates in waters impacted by ocean acidification.

The study by researchers from Stony Brook's School of Marine and Atmospheric Sciences and published in the journal Frontiers in Marine Science, found a “halo” effect of kelp grown in proximity to developing oysters that sharply increased the oysters’ growth by reducing acidification. Without it, the study found, shellfish growth was stunted by acidification, which is caused by increased levels of carbon dioxide dissolving into the oceans. 

Kelp's helpful effect was initially demonstrated in a laboratory, where the team leader, Professor Christopher Gobler, was able to show that kelp could offset the impacts of ocean acidification on shell growth of species such as oysters, hard-shelled clams and blue mussels.

At a conference Wednesday, Gobler said the lab results were “crystal clear.” Oysters exposed to more ocean acidification saw their growth rates “slowed to almost nothing.”

“But by simply co-growing the oysters with the kelp in the lab we could rescue that growth rate and bring it up to the same exact conditions as the same oysters which were exposed to normal pH conditions,” he said.

The next step was proving it in local waters. Stony Brook researchers have been working with a dozen local oyster farmers to pilot kelp cultivation since 2018. Gobler’s team, including Mike Doall, associate director of the university's shellfish restoration and aquaculture program, was able to show the same halo effect of kelp in real-world conditions at the Great Gun Shellfish farm in waters off East Moriches. Newsday has previously reported that Stony Brook, working with Great Gun, showed kelp could grow surprisingly well in shallow waters, a revelation given that kelp generally grows in deeper waters.

Doall said the findings could be significant for oyster farmers, who are on the precipice of their first year of commercially allowable kelp cultivation after passage of a state law allowing cultivation on Suffolk aquaculture leases earlier this year. This week the State Legislature passed a bill that would expand the waters covered for kelp and other seaweed aquaculture to all the waters surrounding Long Island.

Doall said co-locating kelp with oysters “gives these oyster farmers one more reason to add kelp as a second crop.”

Work still needs to be done to make kelp more widely available. It's already used in products from skin care to fertilizers, and some restaurants feature it on the menu, but processing can be complex because kelp has a relatively short shelf life outside of water and is grown from December to May.

At present there are no commercially available seed-stock producers for kelp in New York State. And a program launched by Gobler a year ago to incentivize kelp growing by providing nitrogen credits has gotten off to a slow start, he said.

But Doall said 2022 was a banner year for kelp production, and commercially available licenses and product could help spur the market in 2023.

By Mark Harrington

mark.harrington@newsday.comMHarringtonNews

Mark Harrington, a Newsday reporter since 1999, covers energy, wineries, Indian affairs and fisheries.