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August 1, 2008

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In the Field: Tracing sources of brown tide

Jennifer Smith = |=20 mailto:jennifer.smith@newsday.c= om&subject=3DIn%20the%20Field:%20Tracing%20sources%20of%20brown%20tid= e=20

July 6, 2008

The sun broke through the mist = and turned=20 an overcast summer morning on Quantuck Bay into something out of a = picture book:=20 blue skies over waterfront homes with private docks where herons=20 perched.

But something wasn't right. Instead of being clear, the = water=20 sloshing around the dock pilings was a murky olive, thanks to a type of = algae=20 known as brown tide that had bloomed across the bay.

Blooms like = this one=20 can kill juvenile hard clams and make life difficult for adult = shellfish.=20 Studies show hard clams stop feeding when brown tide cell counts reach = 35,000=20 cells per milliliter of water. "This is where we've seen cell counts of = brown=20 tide upwards of a million cells per liter," said Matthew Harke, a Stony=20 Brook University graduate student who came out on the research = vessel=20 Peconic to collect water samples from Quantuck Bay.

Brown tide is = not=20 known to be toxic to humans. But in high concentrations, algal blooms = shade out=20 the bay bottom. Without light, eelgrass that provides habitat for fish = and=20 shellfish will die, and fish that rely on visual cues to catch prey will = leave,=20 Harke said. "If it's dense enough," he said, "the clams will shut down, = and they=20 won't even feed."

Unwanted guest

Brown tide first hit Long=20 Island in 1985, decimating the scallop population in Peconic=20 Bay. More than two decades later, it keeps coming back, returning = every few=20 years as waters warm. This year, brown tide has clouded South Shore = waters from=20 South Oyster Bay to western Shinnecock=20 Bay, a distance of about 60 miles.

As health officials track = the=20 algae's progression, a research team led by Stony Brook University = professor=20 Christopher Gobler is conducting experiments to better understand how = brown tide=20 thrives and behaves. That morning, Harke and four other students were on = a=20 mission to fill nine 300-liter plastic containers with water from = Quantuck Bay.=20 The boat passed under Ponquogue Bridge and headed west past Tiana Bay. = It moved=20 at a stately 5 miles per hour through the Quogue Canal before dropping = anchor in=20 Quantuck Bay.

First, students recorded the water conditions. They = clocked=20 the temperature, then plunged a white device called a Secchi disk into = the bay=20 to measure visibility: 0.7 meters, or a little more than two feet. At = the back=20 of the boat, doctorate student Florian Koch held a hose steady, filling = the=20 barrels with greenish water that a pump sucked up from the bay through a = deck=20 hatch.

Back at the university's Southampton Marine Station, the = brown=20 tide water will be stored in floating containers in the bay to mimic = natural=20 conditions. Students will introduce various potential predators - clams, = slipper=20 shell snails, other types of plankton - to see which ones eat = Aureococcus=20 anophagefferens, the organism that causes brown tide.

Growth=20 experiment

On the bow, Harke and graduate student Theresa = Hattenrath=20 knelt to fill smaller jugs for the research. Koch plans to introduce = vitamins=20 into the water to see how substances such as nitrogen and phosphorus = affect the=20 growth rate of brown tide. Scientists think Aureococcus anophagefferens = may have=20 an advantage over other algae because it can use organic and inorganic = nitrogen=20 to grow, while most thrive only on inorganic nitrogen. "We're trying to=20 understand the organism and why it does what it does," Harke said of the = work.

It took a little over half an hour to gather all the = samples. Then=20 the boat headed back, moving even more slowly through the canal because = of the=20 extra weight. At the marina, some students pumped the brown tide water = into=20 floating dockside barrels. Harke hustled inside to the center's wet lab = to scrub=20 down slipper shell snails harvested on a previous run. If they're hungry = enough,=20 the snails just might hold the clues to controlling brown = tide.