The voluntary advisory against water contact at Lost Creek Lake was lifted Thursday, more than four months after a blue-green algae bloom triggered public health concerns at Jackson County's largest water body.
Thursday's announcement by Oregon's Harmful Algae Surveillance Program means Lost Creek Lake is the last Oregon water body to get its scarlet A for algae removed.
"Our bloom season is officially over," said Rebecca Hillwig, the program's coordinator in Salem.
Tests on water sampled Jan. 16 showed no cells of blue-green algae, which is a cyanobacteria, Hillwig said. Water sampled the following day showed no detectable levels of toxins that can be present during and after a bloom.
After the requisite week wait, the lake finally received its first clean bill of health since the bloom triggered the advisory Sept. 18.
The advisory lasted 128 days, making it the longest of the season in Oregon, statistics show. A similar advisory at Willow Creek Reservoir in Morrow County lasted 104 days and it was lifted Dec. 27.
Only nine such advisories were issued this year by Oregon public health officials. That's half of the number issued in 2011 and well under the four-year average of 19, according to the state's Harmful Algae Bloom Surveillance Program.
Public health advisories for cyanobacteria are issued based on criteria established by the World Health Organization.
The three most common forms here are anabaena flos-aquae, microcystis and aphanizomenon.
Lost Creek Lake has been plagued with outbreaks of anabaena flos-aquae in recent years, and they have not been traced to a known cause.
The algae may produce toxins that can be dangerous to people and pets, but not every bloom includes toxins. When they do, the toxins are released when the algae dies and dissipates naturally.
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.
No confirmed human illnesses have been tied directly to an algae outbreak in Oregon. However, at least four dogs have died from toxins in water near the Umpqua River near Elkton.
Reach reporter Mark Freeman at 541-776-4470, or email at firstname.lastname@example.org.