Scientists Save Clams, End Brown Tide In Shinnecock Bay: Study

SOUTHAMPTON, NY — A new study indicates good news for the clam population in Shinnecock Bay: A 1,700 percent increase in hard clams, as well as the regrowth of more than 110 acres of seagrass — and the end of brown tides in the bay.

On Tuesday, scientists from Stony Brook University’s School of Marine and Atmospheric Sciences gathered to announce the culmination of a decade of science in a paper published in Frontiers in Marine Science, an international peer-reviewed journal

The study, scientists said, describes a novel restoration approach used in Shinnecock Bay that has led to a 1,700 percent increase in the landings and densities of hard clams in the estuary, along with the expansion of seagrass meadows and the end of harmful brown tides.

The result, organizers of the event said, "brings the Shinnecock Bay back to its 20th century glory for shellfishing — and the result may serve as a shining example of a process to restore other estuaries around the country and world."

The Long Island hard clam was once the greatest fishery in the history of New York State, Stony Brook scientists said. In the 1970s, two out of three hard clams eaten in the United States came from Long Island. Since that time, the fishery had collapsed by more than 99 percent and, despite more than four decades of recovery efforts, the fishery has never responded — until now.

A decade ago, experts explained, Shinnecock Bay was an estuary that was "seemingly irrecoverable. By 2011, the landings of the hard clam, historically the dominant filter feeding bivalve in New York estuaries, had collapsed."

As a keystone organism, the loss translated in a trickle-down effect across the entire estuary, as much of the seagrass across this system had been lost — and harmful and intense brown tides were occurring annually, scientists explained.

And while the situation was emblematic of estuaries across Long Island and across the world, the state of the system seemed particularly dire, scientists said.

“99.5 percent. Sometimes numbers are used as hyperbole, but that is how much the landings of hard clams had declined from the 1970s to 2011 in Shinnecock Bay,” said Stony Brook University Endowed Chair and Professor of Marine Science, Chris Gobler, PhD, and lead author of the study. “These bivalves are known as ecosystem engineers since their ability to filter feed can remove algae, improve water clarity, and have downstream effects on habitats like seagrass meadows that need clear water to thrive. When an estuary experiences a loss of filter-feeding bivalves, the ecosystem-wide effects can be enormous. We knew that a key to recovering this ecosystem would be to re-establish the hard clam population in Shinnecock Bay.”

The path forward came when Gobler, working with his colleague and fellow marine science professor Brad Peterson, kicked off an encompassing ecosystem study of Shinnecock Bay in 2004, aiming to understand the factors constraining clam and seagrass populations and drivers of poor water quality.

Both said that what they discovered was a recruitment-limited population of hard clams, with adults so rare that the odds of successful reproduction were exceedingly low.

The discovery, in part, led to the Shinnecock Bay Restoration Program: The creation of hard clam spawner sanctuaries, regions where adult hard clams would be able to maximize their reproductive output, with their spawn circulating across the entire bay, Gobler said.

To move forward, scientist needed financial support, cooperation from regional officials and baymen, and science, Gobler said, adding that thankfully, all came together.

“The spawner sanctuaries amounted to goldilocks zones. They were far away enough from ocean inlets so the spawn or larvae would not be flushed into the Atlantic Ocean, but not so far away from clean ocean water that the adult clams would perish due to poor water quality,” said Gobler. “Being able to use science to identify the ideal site for locating the spawner sanctuaries was a key to success for this program.”

However, he said, restoration success did not occur overnight. Over a five-year period from 2012 to 2017, more than 3 million adult hard clams were planted in the spawner sanctuaries in Shinnecock Bay, he said.

Given that it takes several years for clams to grow to harvestable size, the rebound of the population was going to take time, he said. But as time passed, the densities of hard clams across Shinnecock Bay did increase, as did the harvests, and in both cases, those increases were primarily among small clams, the precise size of clams what would be expected from the spawner sanctuaries, Gobler said.

In addition, scientists developed a new DNA-based method to track the spawn of the hard clams and demonstrated that they were transported from the western part of the bay to the eastern half of the bay, where densities increased disproportionately. The coupled increase in both clam densities and clam harvests were not fully anticipated by scientists, Gobler said.

“The results of this restoration amount to a win-win for the environment and the economy," said Mike Doall, co-author and associate director of shellfish restoration and aquaculture at SoMAS. “Not only has the health of the ecosystem recovered, but it has helped resurrect a once-thriving hard clam fishery, benefiting the livelihoods of baymen, and restoring an important aspect of Long Island’s maritime history.”

According to Professor Gobler and co-authors of the study, brown tides in New York have contributed to the collapse of bivalve populations and diminished seagrass meadows, and had occurred more frequently and intensely in Shinnecock Bay than anywhere in the world.

But as clams were planted and clam populations expanded, brown tides diminished and then disappeared from Shinnecock Bay, with the system being free of the scourge for six consecutive years, despite their yearly occurrence in neighboring Great South Bay, scientists said.

The turnaround was unprecedented: There had never been a six-year period without brown tide in Shinnecock Bay dating back to before their first appearance in 1985, experts said.

"The successful restoration of Shinnecock Bay has recently led to global distinction for this estuary,” says Ellen Pikitch, PhD, a co-author and endowed professor of ocean conservation science at SoMAS.

In June, the bay was named a Hope Spot by the international organization Mission Blue.

“This honor signals that Shinnecock Bay is a beacon of hope — not only for Long Island — but for areas around the world,” Pikitch said. “We have demonstrated that sustained, science-guided research, restoration and monitoring can undo the damage that has been done, and this is reason for optimism that similar programs elsewhere will also yield positive results."

The research added that there is hope that the success of the Shinnecock Bay is a model to be replicated across Long Island and beyond: In 2017, the New York State Department of Environmental Conservation established the Long Island Shellfish Restoration Program, which replicated the approach in Shinnecock Bay, establishing hard clam spawner sanctuaries in four other locations across Long Island.