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Thursday, September 2nd, 2010
By Nancy Allen
Aerator test results promising
GRAND LAKE - Toxic algae has been choking Grand Lake, but new technology might infuse the air supply needed to save it.
Early signs show giant aerators installed in Grand Lake may be helping heal the algae-plagued body of water, though hard data won't be available for at least two to three months.
This week scientists from two Columbus-area consulting firms gathered data from the lake at Southmoor Shores where an Airy Gator, and a second unit at Park Grand Resort have been operating since April 30. The Airy Gator is designed to infuse oxygen into the lake's sediment, allowing beneficial organisms to grow, eat the organic material and reduce the sediment layer.
"On Aug. 14, I sampled dissolved oxygen levels on the lake and this was the only bay on the whole east side that had levels above 2 parts per million (ppm)," said scientist Henry Pate of Battelle Research Institute.
Oxygen levels of 2 ppm would support creatures such as mussels and different types of worms, he said
And that's a good thing. In a healthy lake, worms and mussels all require adequate oxygen to survive.
"I don't expect to find anything except worms," Pate said. "I'm praying we find mussels."
Pate, and Jennie Morgan and David Strong, environmental scientists with MAD Scientist Associates, will analyze the data from the Southmoor Shores site. Their main goal is to assess how the units are performing and if the technology could be used to treat the entire lake, Morgan said.
The scientists will look at algae counts, flow levels, water clarity, benthos diversity (animals and plants that live at the lake's bottom), dissolved oxygen and ph levels and the sediment profile.
The three scientists rode in a small boat just off the shore to gather data at three sites marked by buoys.
Pate dipped a box core, a clear rectangular-shaped container attached to a pole, into about 3 feet of water to get a sediment sample. He noted there appeared to be an "oxic" layer in the water, a sign the Airy Gator is working. He also saw a large zooplankton, another good sign of organism diversity. The critters also eat blue-green algae in its early stages, he said.
Toxins resulting from the lake's massive blue-green algae blooms this summer caused the state to issue a no contact advisory for the lake. The advisory has since been downgraded to allow boating.
Pate said the Airy Gators could decrease blue-green algae blooms in three ways. First, by moving the water around, which disrupts the formation of floating algae mats. Blue-green algae needs, warm, calm water to grow. Second, by introducing oxygen into the area where sediment and water meet. This makes dissolved phosphorous less available to the algae for food. Third, turning the water over more could expose the algae to additional sunlight which may help break down the toxins.
Blue-green algae is fed by excess nutrients, especially phosphorous. In the 13,500-acre Grand Lake, most excess nutrients run off farmland, which comprises more than 80 percent of the acreage in the watershed.
The buoys will remain at the three sites so the scientist can sample at the same locations each time. They plan to make two more trips to the site within the next four to six weeks to gather data, Morgan said.
The Grand Lake Restoration Commission, a coalition of individuals and organizations from Auglaize and Mercer counties, has raised more than $550,000 in donations to buy the Airy Gators and pay the firms.
The commission also has purchased two Collectors designed to catch sediment in creeks before it enters the lake. One each has been installed in Big Chickasaw Creek and in Beaver Creek and a third should be installed in Barnes Creek later this summer or early fall, commission member Brian Miller said. The commission also plans to analyze the effectiveness of the Collectors, he said.
Pate said toxic blue-green algae is a worldwide problem.
"I know it's no comfort, but the people of Grand Lake shouldn't feel alone; this is happening worldwide," he said. "There's a blue-green algae slick in the Baltic sea the size of Germany as we speak."
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