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Vol. 24, No. 22 May 7, 1999

Researcher Finds Trains and Fish Breeding Grounds While Mapping the Hudson River Floor

BY HANNAH FAIRFIELD

Robin Bell's office at the Lamont-Doherty Earth Observatory overlooks the tree-lined expanse of the Hudson-but she tends to look most at the bottom of the river.

Bell, a marine geophysicist, leads a team of scientists that is mapping the floor of the Hudson River using sonar and other depth-measuring devices. The data they have collected is the first high-resolution imagery of the bottom of the Hudson, along with the first comprehensive readings of the depth of the river and its sediment composition and flow. The data creates a window into the Hudson never before seen.

The research was commissioned by the Department of Environmental Conservation (DEC) and the Hudson River Estuary Management Program to find out what was on the bottom of one of the nation's most traveled rivers.

"A collaboration like this is a first for us," said Bell. "The multi-beam bathymetry system we are using to measure depth is brand new, and we're using it to gather information about the ecology of the river."

Bell's team, along with scientists at SUNY-Stony Brook, mapped the first 20 miles last November, and last month added another 15.

John Ladd, a scientist from the DEC's Hudson River National Estuarine Research Reserve, said his department wants to characterize estuarine habitats and define nursery areas most in need of protection for fishes and blue crab.

"Ranchers, farmers and foresters make extensive use of aerial photography and satellite imagery in managing the land. The geophysical data acquired by Lamont and Stony Brook are analogous data for managing aquatic environments," Ladd said. "For example, some fish spawn by building gravel nests. If we know where there are gravel beds, we know better how to protect the spawning grounds of these fish."

Zebra mussels can be located in a similar fashion, said Suzanne Carbotte, another Lamont marine geophysicist who worked on the project. "Zebra mussels like exposed bedrock," she said, "so we can show the biologists where all the exposed bedrock is under the water."

Last year, when Carbotte and Bell learned that Ladd was looking for geophysicists to gather data on the Hudson, they jumped at the chance to work on a project so close to home.

"I had been working on Antarctic projects for years, and I knew the bottom of the Antarctic ice sheet better than I knew the Hudson," said Bell, a resident of West Nyack, located along the river. "I was eager to see what was down there."

They found buried electrical and telephone cables, construction debris, areas pockmarked with what may be illegally dumped material, boat wrecks and three train cars on their side, just yards from the railroad tracks next to the river.

"It's terrific to see what's under the water as you move over it," said Carbotte. "We called Conrail to see if they had records of any trains derailing and ending up in the water, and people there said that they knew of several incidents," Bell said. "They were almost surprised we hadn't seen more of them."

In November, the research team mapped two stretches of the river-one between Storm King State Park and Wappingers Falls and the other between Kingston and Clermont State Park. Aboard two ships, researchers surveyed 20 miles of the total 130 miles of river that extend from Manhattan's Battery Park to the Troy Locks. This month, they will do an additional two areas: one near Tappan Zee and the other of the Stockport Flats, near Coxsackie. They hope to have the entire project completed a year from now.

The scientists found areas of the river that were deep "holes," as much as 80 feet deep, which Bell said could be protected locations where some fish spend part of the winter. Scientists also mapped the movement of river sediment, the location of swift currents and found some previously unmapped broad, flat areas that are likely nurseries for some fish, such as shad. "With our maps, we can see what areas might need the most protection," Bell said.

Sediment samples, collected by either inserting a long tube into the river bottom or by scooping up material, will help other scientists track river contaminants, such as PCBs. Because contaminants adhere more readily to fine-grained sediments than coarse-grained material, the scientists can identify were pollutant "hot spots" may be. Bell and Carbotte hope the team may soon secure funding for the geochemical analysis on the sediment samples, which would more accurately reveal river bottom contamination.

"When people see the river, they usually just see the surface-they don't see that the bottom of the river is a dynamic system itself," Bell said. She has lived near the river for most of the last two decades, and remembers well her first time sailing on the river in 1980. "The sailboat was a 24-foot cat ketch-we sailed right by Lamont," she said. "The water was really dirty then. It was disgusting when you got close to the city."

Now the river system has cleaned much of itself, even to the point that the DEC is recommending to lift the ban on commercial fishing for striped bass south of Poughkeepsie.

"Now I let my kids swim in the river," Bell said. "We have our own boat and we sleep out on it at least once a week in the summer. It's one of the most beautiful places on earth."