Tom Walker / Deschutes National Forest / Courtesy photoA blue-green algae bloom colors the water near the dam at Wickiup Reservoir last Thursday morning.

Nearly a month after the state issued a health advisory for Wickiup Reservoir south of Bend, blue-green algae remains thick in some places in the water.

“This is kind of unique for Wickiup to be this strong of a bloom this late in the year,” said Tom Walker, a fisheries biologist with the Deschutes National Forest.

The Oregon Health Authority issued a health advisory for Wickiup on Sept. 18, warning against swimming in the reservoir or drinking its water because of toxins from a bloom of blue-green algae. The advisory remained up Tuesday, 26 days after it began.

While summertime recreation, swimming and boating have subsided at the popular reservoir, duck hunters should be careful if they are hunting there with dogs, said David Farrer, a toxicologist with the health authority.

“We would recommend keeping the dog out of the water (until the algae clears up),” he said.

Ducks killed and collected from Wickiup are OK to eat, Farrer said, but he said people should avoid eating their livers. Livers absorb toxins from the algae.

In 2009, Wickiup had two blue-green algae blooms, according to health authority information.

The first lasted 19 days, from Aug. 12 to Aug. 31, and the second lasted 23 days, from Sept. 2 until Sept. 25.

Regularly found in waters around Central Oregon, blue-green algae will take over given the right mix of nutrients, sunlight and stagnant warm water.

The blooms increase the amount of toxins in the water, creating a risk for people and pets — particularly children and dogs. Children and dogs tend to play in water and swallow more water than adults.

Swallowing the toxins may cause numbness, dizziness and nausea within a day of exposure, according to the health authority. Breathing in water droplets may trigger breathing problems, sneezing and coughing. Skin contact with the toxins may result in a rash.

Health officials advise anyone eating fish caught in algae-filled waters to remove all fat, skin and organs before cooking the fish. The toxins tend to collect in this tissues. Wickiup is open for fishing until Oct. 31, according to state regulations.

The health advisory does not extend from Wickiup into the Deschutes River, which the reservoir feeds.

Farrer said tests in the river near the reservoir showed the water is safe.

The health authority issued an advisory for Odell Lake, off state Highway 58, for 18 days, from July 21 to Aug. 8, also due to a blue-green algae bloom. The longest blue-green algae health advisory this summer, for Walterville Pond in Lane County, began Aug. 5. It ended Oct. 2, after 58 days.

The U.S. Forest Service has also recently cautioned visitors to Suttle Lake near Santiam Pass about an algae bloom there, but it hasn’t reached the level to prompt a health advisory, Walker said.

Last week, Walker checked on the algae bloom at Wickiup and found parts of the reservoir still were bright green.

“It’s still going,” he said.

Walker plans to check the reservoir again today and won’t do another test for toxins until the algae has visibly diminished. The health authority won’t lift its advisory until tests show the level of toxins has dropped below a threshold.

“We just have to keep watching until the bloom is gone,” Farrer said.

Although colder weather typically stops an algae bloom, some have persisted through freezing temperatures and continued under ice, he said.

Wickiup doesn’t have a resort, but nearby South Twin Lake does.

The algae bloom at Wickiup hasn’t affected business there because South Twin Lake remains free of it, said Renee Moon, a worker at Twin Lakes Resort.

“It doesn’t really affect us,” she said.

— Reporter: 541-617-7812, ddarling@bendbulletin.com