PORT TOWNSEND — Although toxins are low, Anderson Lake will stay closed for the rest of the season.
Test results of samples taken the weeks of Aug. 27 and Sept. 4 showed that anatoxin-a, a fast-acting and potentially deadly nerve poison, was at a safe level in the lake on Anderson Lake State Park.
After two consecutive safe readings, county public health officials generally recommend lakes be reopened, said Greg Thomason, Jefferson County environmental health specialist.
That recommendation had been made for Anderson Lake after two consecutive tests showed the lake’s level of anatoxin-a to be below the safety threshold of 1 milligram per liter of water.
But Mike Zimmerman, the ranger in charge of the state park, doesn’t trust that the status won’t change for the worse at the popular trout-fishing lake.
The lake has been closed most of the summer because of elevated levels of the nerve toxin created by some species of blue-green algae.
Warm weather is forecast for the end of the week, and since higher temperatures seem to encourage algae growth, Zimmerman is loath to open the lake only to close it again a few days later.
“I’m just not going to do it,” Zimmerman said.
“I’m seeing warm weather coming again. I’m looking at the possibility of having to close again soon.
“This close to the end of the season, it doesn’t do any good for anybody.”
Catch-and-release-only rules came into effect at Anderson Lake on Sept. 1, and the state park west of Quilcene will close at the end of October.
For now, however, the 410-acre state park around the lake remains open for recreation. A Discover Pass is needed to park there.
Thomason also said warmer weather is expected, at least during daylight hours, with temperatures likely to be in the mid-70s.
But he said he feels that algae growth is fueled more by longer days than by warm temperatures.
“It’s supposed to stay pretty warm . . . The other side of that coin is we’re getting shorter days, less daylight,” Thomason said.
“The amount of daylight is the critical thing,” he said.
“We find blooms that start when it’s cold and none when it’s warmer, so it seems to be that the most critical period is the photo period,” which is the amount of daylight between sunrise and sunset.
“There’s less daylight for them to utilize photosynthesis, so that’s slowing them down a bit,” Thomason said.
Blue-green algae is a plant that grows naturally in lakes, especially shallow, older bodies of water.
At times, some species of blue-green algae produces toxins.
Although researchers know that algae growth spikes in the summer when sufficient nutrients such as phosphates are present, they don’t understand what sparks the production of toxins from some species.
Receipt of test results on anatoxin-a levels in East Jefferson County lakes are usually received each Friday, but they were delayed last week and came in early this week.
Anderson Lake was found to have 0.45 micrograms of anatoxin-a, which can cause paralysis and stop breathing, in the most recent test results.
Test results reported Aug. 30 found 0.61 micrograms of anatoxin-a per liter of water.
The lake had been closed Aug. 23 — after having been reopened for fishing and other recreation less than a week earlier — because of a level of 4.9 micrograms of anatoxin-a.
Microcystin, another toxin created by blue-green algae — which has traditionally been low in Anderson Lake — was found to be at a level of 0.34 micrograms per liter of water in the latest test results.
Testing of East Jefferson County lakes will continue through September, Thomason said.
No toxic blue-green algae has been reported in Clallam County, where health officers do not test for toxins; instead, they visually monitor lakes for signs of algae bloom.
Report algae blooms in Clallam County by phoning 360-417-2258.
Report algae blooms in Jefferson County by phoning 360-385-9444.
For more information about lake quality in Jefferson County, visit the environmental health website at http://tinyurl.com/6z64ofy.
Managing Editor/News Leah Leach can be reached at 360-417-3531 or at leah.leach@peninsuladailynews.com.
