Scientists are restoring the devastated clam population and water quality of Shinnecock Bay

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Scientists from Stony Brook University’s School of Marine and Atmospheric Sciences (SoMAS) announced the culmination of a decade of science in a paper published in Frontiers in Marine Science, which describes a new restoration approach used in Shinnecock Bay that has resulted in a 1,700% increase in landings and densities of hard clams in that estuary, along with the expansion of seagrass meadows and the end of harmful brown tides. This result returns Shinnecock Bay to its 20th century clam fishing glory and can serve as a shining example of a restoration process for other estuaries around the country and the world.

The Long Island clam was once the largest fishery in New York State history. In the 1970s, two out of three hard clams eaten in the United States came from Long Island. Since then, the fishery has collapsed by more than 99%, and despite more than four decades of recovery efforts, the fishery has never responded until now.

A decade ago, Shinnecock Bay was an estuary that seemed irreparable. By 2011, landings of the clam, historically the dominant filter-feeding bivalve in New York estuaries, had collapsed. As a key organism, this loss caused a trickle-down effect throughout the estuary as much of the seagrass in this system was lost and damaging and intense brown tides occurred each year. And while the situation was emblematic of estuaries on Long Island and around the world, the state of the system seemed particularly dire.

“99.5%. Sometimes the numbers are used as hyperbole, but that’s how much hard clam landings have declined from 1970 to 2011 in Shinnecock Bay,” said Stony Brook University President and Professor of Marine Science Dr. Chris Gobler. D., and lead author of the study. “These bivalves are known as ecosystem engineers because their ability to filter feed can remove algae, improve water clarity, and have downstream effects on habitats like seagrass meadows that need clean water to are flourishing. When an estuary suffers a loss of filter-feeding bivalves, the effects on the entire ecosystem can be enormous. We knew that the key to restoring this ecosystem would be restoring the hard clam population in Shinnecock Bay.”

The Stony Brook scientists also knew the task of restoring the hard clams would not be easy, as over 40 years of previous efforts had largely failed. A new approach was needed, based on science and tailored to the specific nature of Shinnecock Bay.

The road to recovery

Working with fellow marine science professor Brad Peterson, Gobler undertook a comprehensive study of the Shinnecock Bay ecosystem in 2004 to understand the factors limiting mussel and seagrass populations and the causes of poor water quality. What they found was a limited population of hard clams, with adults so rare that the chances of these radiating individuals successfully reproducing were extremely low. That discovery in part led to the basic approach to what became a central effort of the Shinnecock Bay Restoration Program: the creation of hard clam spawning refuges, regions where adult hard clams could maximize their reproductive output, with their spawn circulating throughout the bay.

To optimize the creation of spawning refuges, scientists needed three important components: financial support to implement the plan, cooperation from regional officials and beymen, and careful science to identify the ideal location for the refuges and to monitor progress. Fortunately, all of these components came together.

Nine years of support for the project was generously provided in large part by the Laurie Landeau Foundation with additional support from the New York Department of Environmental Protection. The Town of Southampton Trustees worked with scientists from Stony Brook University and the Town of Southampton Baymen’s Association to identify regions that would be no-take zones where harvesting of clams is prohibited so that planted adult hard clams can repopulate bay without being poached. Finally, the scientists identified regions that would maximize the ability of adult clams to reproduce and the retention of their hatchlings in the bay.

“The spawning grounds were tantamount to gold panning zones. They were far enough from ocean inlets that spawn or larvae would not be washed into the Atlantic, but not so far from clean ocean water that adult clams would die due to poor water quality,” said Professor Gobler. “The opportunity to use the science of identifying the perfect place to locate spawning dens was key to the success of this program.”

Turning the tide

Recovery success did not happen overnight. Over a five-year period (2012-2017), more than 3 million adult hard clams were stocked in Shinnecock Bay spawning reserves, and given that clams take several years to grow to size, harvestable, population recovery was taking time. But over time, the density of hard clams in Shinnecock Bay increased, as did the harvest, and in both cases these increases were mostly among small clams, the exact size of clams that would be expected from spawning refuges.

In addition, the scientists developed a new DNA-based method for tracking hard clam spawn and demonstrated that they are gradually transported from the western half of the bay to the eastern half of the bay, where densities increase disproportionately. The combined increase in both clam density and clam harvest was not fully predicted by the scientists.

“The results of this recovery are win-wins for the environment and the economy,” said Mike Doal, co-author and associate director of shellfish recovery and aquaculture at SoMAS. “Not only did ecosystem health recover, but it helped resurrect a once-thriving hard shell fishery, benefiting bay livelihoods and restoring an important aspect of Long Island’s maritime history.”

According to Professor Gobler and co-authors, brown tides in New York contributed to the collapse of bivalve populations and the decline of seagrass meadows, and occurred more frequently and intensely in Shinnecock Bay than anywhere else in the world. But as clams were planted and clam populations expanded, brown tides gradually declined and then disappeared from Shinnecock Bay, the system being scourge-free for six consecutive years, despite their annual appearance in neighboring Great South Bay. There has never been a six-year period without a brown tide in Shinnecock Bay dating back to their first appearance in 1985.

“The successful restoration of Shinnecock Bay has recently led to a global distinction for this estuary,” said Dr. Ellen Pikich, co-author and endowed professor of ocean conservation science at SoMAS.

In June, the bay was named a place of hope by the international organization Mission Blue.

“This honor signals that Shinnecock Bay is a beacon of hope – not just for Long Island – but for areas around the world,” adds Pikitch. “We have shown that sustained, science-led research, restoration and monitoring can reverse the damage, and this is cause for optimism that similar programs elsewhere will also produce positive results.”

The research team emphasizes that there is hope that Shinnecock Bay’s success is a model that can be replicated on Long Island and beyond. For example, in 2017, NYSDEC established the Long Island Mussel Recovery Program, which mimics the approach in Shinnecock Bay by creating sanctuaries for hard clams that spawn at four other locations on Long Island.


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More info:
Christopher J. Gobler et al, Rebuilding A Collapsed Bivalve Population, Restoring Seagrass Meadows, and Eradicating Harmful Algal Blooms in A Temperate Lagoon Using Spawner Sanctuaries, Frontiers in Marine Science (2022). DOI: 10.3389/fmars.2022.911731

Courtesy of Stony Brook University

Quote: Scientists recover collapsed mussel population and water quality in Shinnecock Bay (2022, August 30), retrieved August 30, 2022, from https://phys.org/news/2022-08-scientists-recover-collapsed -clam-population.html

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