Wednesday, June 30th, 2010
Algae's origin a mystery
By Nancy Allen
Aphanizomenon has become the dominant type of algae in the lake, taking over the already known planktothrix. But why this new species suddenly emerged seemingly overnight remains a mystery.
The species is producing a liver toxin (cylindrospermopsin) and a neorotoxin (saxitoxin). Planktothrix produces a toxin called microcystin.
Though both algaes are toxic, the aphanizomenon creates a foul-smelling, thick, mat of scum on the lake. Planktothrix is much less visual, giving the lake water a consistent cloudy green color.
There is no way to know what caused the lake to switch algae species, said Robert Hiskey, a biology professor at Wright State University-Lake Campus. Hiskey has studied the lake's algae for many years. Planktothrix had been the dominant algae for the last five.
"Last April the mix of algaes in the lake was wonderful and diverse," Hiskey said. "Different algae species go through cycles where some are more dominant than others. It's hard to know why it flipped."
Last fall and early this spring, the lake also experienced the best clarity it had in years. People reportedly could see into the water 4 feet.
Hiskey said the new algae likely was already present in the lake in small amounts, though he had never seen it. Since it is not a true algae, but rather a bacteria, it can multiply profusely in a short period of time, he said.
The blooms on Grand Lake started about three weeks ago and seem to appear overnight or even within hours. The blooms come and go and can arrive one day and be gone the next.
Though not a rare algae overall, Linda Merchant-Masonbrink, harmful algal coordinator for the Ohio EPA, said she hasn't seen aphanizomenon in Ohio since the late 1970s in Lake Erie.
"I'm sure it's in other places (in Ohio)," she said. "We just haven't looked."
The EPA only tests for algae species if a problem is reported, as was the case with Grand Lake.
There is no evidence that shows inhaling the algae stench is harmful and the lake's fish also are not affected.
There also is no way to predict how long this new particular species will continue fouling the lake.
"As long as there are nutrients there, there is going to be algae," Hiskey said. "It might flip (species) or it might not."