Barnegat Bay hit by brown tide in south end

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Algae chokes native life

By KIRK MOORE • STAFF WRITER • September 13, 2010

This late summer's drought brought brown tide back to the southern reaches of Barnegat Bay, spreading a coffee-colored stain around the Route 72 causeway as billions of micro-organisms choked native life in the bay, scientists found in late August.

The outbreak was discovered only by chance, as the state Department of Environmental Protection stopped watching for brown tide in 2004 to save money.

"This is the kind of summer where brown tide has been a problem in the past," said Michael Kennish, a research professor who leads Rutgers University research on Barnegat Bay's problems.

Extreme dry conditions — with little rain, lower freshwater stream flows in bay tributary streams and higher salinity levels in the bay — typically set the stage for explosions of brown tide, Kennish said.
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When those algae crowd the bay, they shut down clams and bay scallops that feed on most kinds of tiny aquatic plants, said Monica Bricelj, a Rutgers research professor who studies harmful algae blooms.

"Essentially they starve," Bricelj said, because the brown tide organism interferes with shellfish organs that pump nutrients through their bodies. The smallest juvenile shellfish are most at risk because they cannot survive long without food, she said.

Newborn clams in their free-swimming larval state get hit by brown tide, too, because the blooms delay their growth, Bricelj said.

"Even if they don't die, they spend more time in the (floating) plankton and get eaten up by predators," she said.

DEP workers spotted the bloom during a routine aerial survey around Aug. 19, Kennish said. Those patrols use sensors to detect chlorophyll-A, a plant pigment that indicates algae blooms.

But brown tide does not give off a chlorophyll-A signature, Kennish said.

"That's why brown tide is so problematic," he said. After the aircrew reported seeing the bay stained near the Manahawkin section of Stafford, Rutgers workers and a student from the New Jersey Institute of Technology took samples to make a positive identification.

An analysis at the NJIT laboratory in Newark showed brown tide at concentrations up to 250,000 cells per milliliter of water — dense, but not so bad as 2 million-cell counts recorded during the drought of the early 2000s.

From 1995 to 2004 the DEP conducted regular brown tide monitoring, when frequent outbreaks plagued fishermen growing seed clams to market size on the bay bottom near Tuckerton.

Scientists think brown tides are just one factor in the demise of Barnegat Bay's native clam beds and underwater eelgrass, which suffers when densely discolored water blocks out the sunlight it needs to grow.

"In 2006 we had a terrible year for sea grasses. We saw a lot of discolored water then," Kennish recalled. "But the state stopped monitoring brown tide blooms in 2004 for lack of funding. They probably should be monitored every two weeks."

Clams may be suffering from changes in the bay's mix of algae, Bricelj said. That's been seen in the South Shore bays of Long Island, where smaller forms of green and blue-green algae supplanted other species and now provide less nutrition for shellfish, she said.

"So there's definitely something going on with the food supply," Bricelj said.

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