Study of post-Sandy waters surprises researchers
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A series of offshore sand ridges hundreds of feet long cushioned parts of Fire Island and Long Beach from severe erosion during Sandy, researchers have found as they start to see results from studies undertaken after the storm.
Post-Sandy water samples show that retreating tides during Sandy swept pollutants into the ocean far off shore. And levels of zinc, copper and lead increased dramatically in the waters near the Bay Park Sewage Treatment Plant and in Reynolds Channel north of Long Beach, according to research from colleges working jointly to study Sandy's environmental impacts.
Those results surprised researchers and opened up new questions about the impact of the storm and what it may mean regionally for future storms.
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"What we found was quite different than we expected," said John Goff, a senior research scientist at University of Texas at Austin's Institute for Geophysics.
Scientists in January and February used radar and seafloor mapping technology to measure where and how deeply sand was deposited by the storm and how the ebb tide impacted ocean areas off Long Beach and in the west and east ends of Fire Island.
Researchers also drew sediment samples in offshore areas, bays and Reynolds Channel, into which the storm-crippled Bay Park treatment plant sent more than 2 billion gallons of raw or partially treated sewage.
The research with Adelphi University, Stony Brook University and the City College of New York was financed through a fund at the University of Texas and a grant from the National Science Foundation. The scientists are pursuing funding to continue their studies and said they hope to revisit the Long Island sites to compare results from this year with future samples.
In one component of the work, the group studied the shore face -- the ramp of sand that slopes away from the barrier islands and levels off as it approaches the continental shelf.
They expected to find heavy erosion like that seen along the coast of Texas when Hurricane Ike hit in 2008. Instead, the study found parts of Fire Island and Long Island were protected by ridges of sand about 1 kilometer -- roughly 0.6 miles -- offshore that ranged in height from about 61/2 feet to 13 feet, and hundreds of feet long in water 45 to 65 feet deep.
"These sand ridges, where they exist, kind of protect the shore face," Goff said. "They really seemed to cushion the blow."
Sand ridges were not found near the area where Sandy carved a new breach through the Fire Island National Seashore wilderness area.
That these ridges served as a buffer could have implications for sand replenishment projects, Goff said. "These sand ridges are often seen as an area to borrow to replenish," he said. "It might be better to borrow sand from further offshore."
Researchers also found mud offshore that had likely been moved out of rivers, creeks and bays into the ocean.
"We did not expect to see mud in a shallow offshore area, but we did," said Beth Christensen, director of the Environmental Studies Program at Adelphi University. "It looks like what happened is the storm stirred up mud and redeposited it farther offshore."
Sediment samples drawn off Fire Island and Long Beach were found to contain toxins likely carried out to sea by Sandy's strong receding, or ebb, tide.
"What we are seeing are elevated concentrations of copper, zinc and lead offshore, as well as other heavy metals," Christensen said. "These metals definitely came from the bays and were deposited offshore."
What is unclear is if the toxins move out to the ocean routinely or if only big storms are the cause -- and what that means for fisheries, she said.
The same metals were also found in sediments in the western bays and Reynolds Channel and are typically associated with sewage processing, said Cecilia McHugh, a professor in the School of Earth and Environmental Sciences at Queens College.
"It's getting trapped in the bays," she said.
Scientists would normally see levels of lead at 30 parts per million, but saw up to 200 parts per million. For copper, the background level is typically 20 parts per million, but it reached 280 parts per million. And for zinc, which would naturally be found at about 50 parts per million, the concentration was up to 300 parts per million.
"For a bay, it's not a good thing because the bay does not get the flushing that the inlets do," McHugh said. "The bays are much more enclosed."
Researchers plan to publish a peer-reviewed, verified report of their results next year.