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On LI’s southern coastline, Sandy’s impact is still in evidence

Great South Bay’s ecosystem is altered by breach that superstorm ripped out of Fire Island five years ago.

The breach on Fire Island, just south of

The breach on Fire Island, just south of Bellport Harbor, and seen here on Oct. 10, 2017, was created during superstorm Sandy in 2012. Photo Credit: AllIslandAerial / Kevin P. Coughlin

When superstorm Sandy roared ashore five years ago it flooded streets, damaged thousands of homes and knocked out power for weeks across Long Island.

It also altered the coastline, cutting three holes in Fire Island.

Two of those breaches on the barrier island were filled in by the U.S. Army Corps of Engineers shortly after the 2012 storm. But one remains open to the sea, and it’s changing the environment even today.

Salinity levels in the Great South Bay have risen and scientists have documented an increase in salt-loving and migratory species there.

They have also found evidence of fish moving from ocean to bay more often than in the past, when the only openings to the bay were from the Fire Island and Moriches inlets on either end of the 32-mile-long island.

“The ecosystem is really still adjusting to the breach and the salinity changes in the bay,” said Janet Nye, an assistant professor at Stony Brook University’s School of Marine and Atmospheric Sciences.

Chief among the changes: More lady crabs, fewer blue crabs.

Traditionally found only near Fire Island Inlet, lady crabs — known for their reddish purple spots — were plentiful during the post-Sandy surveys.

“With the breach, they spread out across the entire bay,” said Bob Cerrato, also an associate professor at SoMAS.

Every spring, summer and fall from 2013 to 2015, Nye, Cerrato and their SoMAS colleagues went out on trawlers and dropped nets randomly in 30 to 45 locations of Great South Bay, counting the catch and then releasing it back into the water.

As part of the study — funded by state Department of Environmental Conservation, New York Sea Grant and National Park Service — they compared the data with a similar survey done of Great South Bay in 2007.

Numbers of predators like summer and windowpane flounder, striped bass, sea robins, bluefish and mantis shrimp also increased compared to 2007.

“There’s basically more of these large predatory fish,” Nye said.

Horseshoe crabs also increased.

The findings indicate that the opening — in a remote, protected section of the Otis Pike wilderness area, across from Bellport Bay — is fostering a more connected and mature ecosystem than found a decade ago. Mature ecosystems have more organisms, or diversity.

“It means that the system is larger than just the bay is and will tend to be more resilient,” Cerrato said.

Diversity and abundance of species also means a more complex food web, with more things upon which to feed. If one species succumbs to disease or is overfished, the results are not so drastic.

“The more connectivity there is ... the more stable the system will tend to be, just because if you break one link, there are still other linkages happening,” Cerrato said about the diversity of species.

The researchers also measured salinity levels, which before Sandy typically hovered at 24 to 25 parts per thousand. But in the eastern part of Great South Bay, levels were between 31 and 32 parts per thousand during the 2013-2015 surveys. Ocean water is generally at 32 parts per thousand, Cerrato said.

While the breach has shifted, narrowed and widened as storms and waves come and go, sand stopped being deposited by the sea into the bay after about 18 months, said Cheryl Hapke, a research coastal geologist with the U.S. Geological Survey’s Coastal and Marine Science Center in St. Petersburg, Florida.

“There’s no longer any increase to the volume of the sand in to the bay,” Hapke said.

Still, the future of the breach is an unknown. Waves, wind and tidal flows lead to an ever-changing system that forms spits and sandbars, but then erode again before the process starts over.

A USGS report published in September and authored by Hapke said the breach is a “quasi-stable” system but it’s unclear how long it will remain open. USGS is currently working with a Dutch modeling firm to try to predict conditions that would lead the breach to close or one to open. The data are under review and not yet public.

When hurricane-turned-tropical-storm Jose neared Long Island in September, the waves removed a lot of the sandbars that had formed in the mouth of the breach on the bay side, said Charles Flagg, an adjunct professor and principal investigator at SoMAS.

“The exchange with the ocean appears to be a little bit more,” Flagg said. “It’s not an overwhelming change, but it’s a change.”

Researchers say the breach is likely still evolving and it’s unclear when or if the ecosystem will stabilize or continue to change.

“We don’t know when or how long it will take to settle into things or if it ever will,” Cerrato said.

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