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Mar 4, 2009 11:14 AMPublication: The Southampton Press

Mill Pond problems may have been caused by effort to prevent algae

Mar 4, 2009 11:14 AM

High levels of phosphorus suspended in the waters of Mill Pond in Water Mill is being blamed for a massive algae bloom that killed thousands of fish late last summer, and now the Southampton Town Trustees say water-agitating devices they approved for use there might have created the problem.

The Trustees stopped short of blaming the die-off on the devices, called SolarBees, but said at a meeting on Tuesday that water samples taken by scientists from the U.S. Geological Survey showed a spike in the levels of phosphorous in the pond last summer. They said they fear the SolarBees, installed at Mill Pond to agitate the water and prevent algae blooms, may have stirred up phosphorus that had settled at the bottom of the pond over many years, feeding the immense bloom that was observed there just before the die-off.

“We’re trying to determine where [the phosphorus] might have come from,” Board of Trustees President Jon Semlear said. “It’s possible that it may have been re-suspended.”

Mr. Semlear said the SolarBees were in the pond in 2007 but were not working properly at that time. They were sucking up weeds and plant material from the bottom of the pond. The SolarBees were installed again in the spring of 2008.

The Trustees, who manage all the town’s freshwater bodies, are due to vote later this month on whether the four SolarBees machines, which are rented by a group of residents who live on the pond, may be installed again in 2009.

“Our intention is to poll the board at the next meeting, but at this point it does not appear that there is support to reinstall them,” Mr. Semlear said.

Steve Abramson, a member of the Friends of Lake Nowedonah, the group of neighbors that has paid nearly $90,000 for the SolarBees project in hopes of improving the water quality in the lake, said that he hopes the machines will be given another chance.

“We would pull them if we thought they were causing harm,” he said, noting that there has been no actual evidence that the SolarBees were related to the heightened phosphorus levels or that last year’s algae blooms and fish die-off were anything but a natural anomaly. “This is not a fair and proper testing of what they can do. It would be premature to pull the plug on this investment in the health of the pond.”

An aquatic ecologist, hired by the SolarBees manufacturer, told the Trustees in December that the low oxygen levels that killed the fish could have been caused by a natural inversion of the water in the lake that pushed oxygen-starved water to the surface, rather than phosphorus stirred up by the agitators.

Chris Gobler, Ph.D, a professor at Stony Brook University’s School of Marine and Atmospheric Sciences who has done extensive work in the waters on the East End, has said that he thinks the algae bloom was actually sparked by high nitrogen levels in the pond, not phosphorus.

Nutrients like nitrogen and phosphorus, a byproduct of fertilizers and car exhaust, can spur algae blooms when flushed into ponds and bays by stormwater runoff from adjacent roads, lawns and farm fields. Mill Pond, which is surrounded by residential development and is downhill from several large farm fields, has long suffered from algae blooms that turn its waters green each summer.

In the week before the fish die-off, Dr. Gobler’s graduate students recorded a massive algae bloom in the pond, the largest they had ever observed there. At the same time, the USGS water sampling showed super-elevated levels of phosphorus in the pond water.

The night before the die-off, on September 20, the USGS data shows temperatures dropped significantly for the first time that fall, according to the Trustees. The falling temperatures may have killed the algae, and the decaying process of the massive amounts of algae would suck oxygen out of the water, asphyxiating the fish.

On the day of the die-off, however, Dr. Gobler, who discovered the dead fish, said that it didn’t appear the algae had died yet.

The Trustees said on Tuesday that they are embarking on a comprehensive monitoring of conditions at the pond this year. They said they are going to have water samples taken weekly throughout the spring, summer and fall.

“We hope to put together a scientific profile of what happened there,” Mr. Semlear said. “It’s a godsend to have Chris Gobler and a student body of experts. That’s a lot of experience right here at the college.”

The Trustees are also considering treating the pond waters with alum, a mineral that bonds with phosphorus suspended in the water column and sinks it to the bottom. The Trustees have applied to the state Department of Environmental Conservation for permission to spread alum in the pond and say they have been assured it is environmentally safe.

Mr. Abramson said that until the SolarBees are shown to have caused the fish die-off they are the most environmentally sensitive way to address the problems at the pond. He said that in his own research he has found evidence that the alum treatments likely won’t be effective at Mill Pond, and could even cause another fish die-off.

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houses are built,people move in, people poop, poop has nitrogen hello?
By local (106), north sea on Mar 9, 09 9:44 PM