Advisory warns of blue-green algae bloom at Lost Creek Lake
Blue-green algae has reared its potentially toxic head again at Lost Creek Lake, triggering a public-health advisory against water contact by people or pets at Jackson County's largest reservoir.
The Oregon Health Authority on Thursday issued the volunteer advisory — currently the only one in Oregon — after the discovery of a large bloom of the cyanobacteria at the reservoir that feeds the Rogue River.
U.S. Army Corps of Engineers field crews Monday abruptly discovered a large mat of bluish-green material near the spillway access area along the dam's southwest side, says Justin Stegall, the Corps' natural-resource specialist at the project.
"It was pretty dense," Stegall says. "I was pretty surprised it came on like it did."
Tests on water sampled Tuesday showed the presence of two forms of cyanobacteria commonly referred to as blue-green algae that bloom regularly at this Rogue River reservoir 30 miles north of Medford, according to the Corps.
Tests showed 197,629 cells of Anabaena flos-aquae per milliliter of water, according to the Oregon Health Authority. The unhealthy threshold of that strain is 100,000 cells per milliliter.
That strain of cyanobacteria can produce potentially dangerous toxins, particularly when the bloom dies off. But not all blooms are toxic.
The most prevalent of the species discovered this week in the reservoir was aphanizomenon, which showed 2.3 million cells per milliliter of water, according to the OHA.
But aphanizomenon was taken off the harmful algae list in 2011 after it was determined that the strain in Oregon does not produce harmful toxins, said Rebecca Hillwig, an OHA environmental health specialist.
The advisory was enacted solely for the presence of anabaena flos-aquae, whose outbreaks in Oregon tend to be shorter than other strains of cyanobacteria, records show.
Similar blooms occur regularly at Lost Creek in the fall, most often starting in late September, records show.
"It was a little later than normal," Stegall says. "Hopefully, it won't stick around very long."
History, however, suggests otherwise.
Algae blooms have been a fall and winter bane at Lost Creek Lake and sometimes the blooms can stretch over several months. The longest lasted 134 days in 2008-09.
During advisories, people and pets are warned to avoid water contact, but compliance is voluntary. Anglers are encouraged to practice catch-and-release fishing during advisories.
Exposure to toxins can produce numbness, tingling and dizziness that can lead to difficulty breathing or heart problems that require immediate medical attention. Symptoms of skin irritation, weakness, diarrhea, nausea, cramps and fainting also should receive medical attention if they persist or worsen.
Children and pets are at increased risk for exposure because of their size and level of activity.
No confirmed human illnesses have been tied directly to an algae outbreak in Oregon. However, at least four dogs have died in recent years from toxins in water near the Umpqua River near Elkton.
The cause of the Lost Creek Lake blooms is unknown, but they have been part of the landscape at the reservoir since Oregon health officials began charting such blooms more than a decade ago.
Reach reporter Mark Freeman at 541-776-4470 or firstname.lastname@example.org. Follow him at www.twitter.com/MTwriterFreeman.