What makes Anderson Lake so unusually toxic? Scientists to try to find answer
Map by Keith Thorpe/Peninsula Daily News
By Jeremy Schwartz
Peninsula Daily News
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The goal: to try to find out why one of the North Olympic Peninsula's most popular fishing spots has been plagued since 2006 by soaring levels of anatoxin-a, a potent nerve toxin produced by blue-green algae.
In June 2008, the 60 acres of lake within Anderson Lake State Park near Port Townsend contained the highest level of anatoxin-a ever recorded in the world: 172,640 micrograms per liter.
The safety threshold for the toxin, which can kill in four minutes after ingestion, is 1 microgram per liter.
With funding in part from the state Department of Ecology and water sampling help from Jefferson County Public Health, researchers at Oregon State University are scrutinizing types of blue-green algae that live in Anderson Lake.
It's a project that could produce results as soon as this December, said professor Theo Dreher, chairman of the Department of Microbiology at Oregon State University and lead researcher.
They are analyzing the DNA of a few specific types of blue-green algae, called cyanobacteria, taken from Anderson Lake to see if they are commonly found in similar freshwater lakes across northwest Washington.
If not, this would suggest Anderson Lake is home to a specific variety of toxin-producing cyanobacteria not found in other lakes, Dreher said.
That could account for the high toxin production, he added.
This information could help local health officials devise a plan to combat the specific type of cyanobacteria and potentially reduce Anderson's toxin levels, he said.
“If they determine that's true, there may be things we can do to treat that in Anderson Lake,” said Greg Thomason, Jefferson County environmental health specialist.
Blue-green algae occurs naturally and is usually benign, but at times, certain types will begin pumping out toxins.
Researchers don't know why.
They know only that warmer weather and longer days tend to fuel the growth of blue-green algae when the lake contains enough nutrients, such as phosphorus.
Anderson Lake has been tested for toxins since two dogs that lapped water from the lake died Memorial Day weekend in 2006.
Since then, the lake, a favorite for trout fishing, has been closed periodically to recreation and fishing during the warmest times of the year because of elevated levels of anatoxin-a and microcystin, a slower-acting poison that can cause skin irritation if touched and liver damage if swallowed.
In 2012, the lake was open only a few weeks of the year and surprised researchers by showing climbing levels of anatoxin-a in September and October, when cooler weather and shorter hours of daylight would be expected to quell algae production.
The statewide lowland lake fishing season begins Saturday. State Ranger Mike Zimmerman, who is in charge of Anderson Lake State Park, will decide this week if the lake will be reopened for recreation then.
In the meantime, Dreher said Thursday that his initial research has suggested a specific few varieties of Anabaena cyanobacteria may be responsible for producing anatoxin-a in high quantities, though he said these results are still preliminary.
“So what's making most of the anatoxin there will need some more work and confirmation,” Dreher said.
Blue-green algae relatively unique to Anderson Lake being responsible for the anatoxin-a is one of two hypotheses that Dreher is exploring to explain the lake's high toxin levels.
The second hypothesis says the conditions in Anderson Lake are somehow just right for the production of anatoxin-a, rather than an individual variety of cyanobacteria being the culprit.
If blue-green algae found in Anderson is common to similar lakes, this line of evidence would point toward the second hypothesis, Dreher explained, adding that this route would require additional study.
“We're not going to experimentally address [the second hypothesis] until we're forced to by the first one being ruled out,” Dreher said.
A county report released in February notes the high amount of phosphorus in Anderson Lake as opposed to other lakes in the county, such as Gibbs or Leland.
A dairy farm was operated near the lake for more than 50 years, said Thomason and Michael Dawson, water quality lead with the Jefferson County Public Health Department, in the report.
“Cow manure is very high in phosphorus and is probably the major source of the high phosphorus levels in this small lake,” the report says.
For the past few years, Dreher has been leading a team of undergraduate, graduate and post-doctoral students in sampling and studying blue-green algae in lakes across northwest Washington.
As part of this work, Dreher said, he and his students found “quite interesting situations” where similar lakes were found to have varying levels of specific algae-produced toxins, or none at all.
Anderson Lake stood out in these studies because consistently high levels of both anatoxin-a and microcystin have been seen there.
“Anderson Lake just looked very interesting very early,” Dreher said.
Other lakes tested in East Jefferson County — such as Leland, Gibbs and Crocker lakes — occasionally have been found to contain unsafe levels of anatoxin-a and microcystin, but not in the amounts historically seen in Anderson Lake.
Toxin-producing blue-green algae has not been spotted in Clallam County.
Reporter Jeremy Schwartz can be reached at 360-452-2345, ext. 5074, or at firstname.lastname@example.org.
Last modified: April 20. 2013 6:06PM