Bitter cold weather that has gripped Southern Oregon for the past two weeks appears to have knocked down a persistent blue-green algae bloom at Lost Creek Lake, where an advisory against water contact could be lifted as soon as today.
Vast mats of the cyanobacteria anabaena flos-aque seen as recently as two weeks ago near the Lost Creek dam spillway have all but dissipated from Jackson County's largest water body, according to the U.S. Army Corps of Engineers.
Water samples were taken Monday for analysis of algae levels and the presence of toxins associated with them. If the tests reveal levels below Oregon's public-health thresholds, the volunteer advisory against water contact, which has been in effect for 98 days, could be lifted.
"It seems like this bloom has been going on forever," said Justin Stegall, the Corps' natural resources manager at the reservoir. "It would be great to get it over and not get it back."
This is the sixth consecutive year that a fall bloom of blue-green algae has led to an advisory at the lake, with each one starting in September and most stretching well into January.
The longest lasted 134 days in 2008-09. The shortest was 25 days in 2009.
If the current advisory were to end today, it would be only the second fall bloom at Lost Creek to last fewer than 100 days, records show.
The only other lake in Oregon with a current blue-green algae bloom is Willow Creek Reservoir in Morrow County, which was issued Oct. 25.
An advisory at Fern Ridge Reservoir near Eugene was lifted Wednesday.
Twelve advisories have been issued this year in Oregon, with Lost Creek and Willow reservoirs this year's only repeat offenders.
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 about a decade ago.
During advisories, people and pets are warned to avoid all water contact, but compliance is voluntary. Anglers are encouraged to practice catch-and-release fishing during advisories.
Toxins cannot be filtered by standard camp filters or by boiling the water. In-home filtering systems cannot cleanse the water, though public treatment plants can reduce algae toxins through filtration and disinfection.
People who eat fish from algae-tainted waters should remove all fat, skin and organs before cooking, because toxins can collect there. People should not eat crayfish or freshwater shellfish taken from infested lakes during an advisory.
Not all blue-green algae strains produce toxins dangerous to people or pets, and not all blooms release toxins.
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.
Reach reporter Mark Freeman at 541-776-4470 or firstname.lastname@example.org.