Warmer weather is holding on longer this year, while water levels drop. That spells more prevalent blue-green algae blooms in larger lakes and reservoirs, prompting a warning from their management agencies — stay out of the water, at least, for now.
The National Park Service on Monday announced the waters of Blue Mesa Reservoir — so far only at Iola Basin — had higher levels of cyanotoxins than what the state deems safe. On Wednesday, Colorado Parks and Wildlife issued a similar caution for the Dome Lakes State Wildlife Area, Saguache County.
“It’s becoming more common in the late summer, with the water being lower and warmer, as is kind of a trend. We’re definitely starting to see a lot more of it in the Southwest,” said John Livingston, spokesman for Colorado Parks and Wildlife’s Southwest Region.
“Statewide, we are starting to see it is a little more prevalent.”
At Upper Dome Lake in the State Wildlife Area, the levels tested out at 7.5 microgram per liter, or ug/l, of microcystin (a primary algal toxin). Although that is just below the threshold of 8 ug/l, CPW decided to post warning signs and prohibit getting into the waters, Livingston said.
“This isn’t a full-blown closure. It’s a caution. We don’t want people recreating in the water.”
The exact levels at Iola were not available, but samples there exceeded state thresholds on Friday, Sept. 10, and NPS issued an advisory and posted warnings, said Dan Johnson, acting manager of Interpretation, Education and Technology for Black Canyon of the Gunnison National Park and Curecanti National Recreation Area.
“This year, we’ve got lower water levels,” said Johnson. “We’ve had a really warm summer, which is one of the things that causes the levels to go up. If there was regular volume of water in the reservoir, it would be a little better.
“There is always potential for it.”
The heat is lasting later into the year, Livingston noted, citing September temperatures in the 90s.
The NPS and CPW are continuing to monitor toxic algae levels and will reopen the areas to in-water recreation when it is deemed safe.
People can still recreate near the lakes, but swimming, wading, boating, paddle boards and the like are prohibited because of the toxins, which can cause serious illness in humans and can be lethal to pets.
At Blue Mesa, the restriction applies only to Iola Basin, on the eastern part of the reservoir.
“Other parts of Blue Mesa are fine,” Johnson said. The NPS cautions people to be on the lookout for the algae at other areas, just in case, and to avoid suspected algal mats.
Algae occur naturally and it is not possible to remove the blooms in waterways the size of Blue Mesa. Algae are not uncommon in open water, but when their toxicity exceeds what is safe, it is vital to stay out of the water, particularly for kids and animals.
“The key thing is avoiding contact with the water in that area, things like water recreation, like swimming, (water) skiing and paddle boarding,” Johnson said. “If someone were to get exposed, you want to shower in clean water as soon as you can.”
A pet that gets into contaminated water should also be promptly bathed in clean water and taken to a vet. People should monitor for adverse reactions, which range from mild rash and nausea, to seizures and breathing problems.
“Toxic algae can be really serious. Pets have died from swimming in it. It’s definitely not something to mess around with,” Johnson said.
The NPS manages Blue Mesa Reservoir, although CPW manages the fishery there. The agencies routinely keep in touch with each other when they detect cyanotoxins.
Although people need to stay out of the water, they can fish from safe locations on the shore. It is OK to eat fish caught at Upper Dome or Iola, provided they are cleaned and cooked properly, because the toxins accumulate in liver and guts.
Anyone who isn’t comfortable eating fishing caught in those waters should simply avoid doing so, Livingston said.
The toxicity levels can change rapidly.
“With these blooms, these can change hour to hour, even. They will be tested regularly,” he said. “Those signs might come down as early as (Thursday). It might be a week from now. It’s kind of an ever-changing process. We just want people to be aware of the toxin being higher than what would be safer for pets and humans.”
People can do their part to mitigate blue-green algae by making sure substances like lawn fertilizers, dog or other pet waste and urea-based de-icers are kept out of the waters.
“We haven’t found a way to get rid of it yet,” Livingston said.
“For right now, we have to let it run its natural course. What we’ve seen is that cooler temperatures, when they come in, they kind of help with that. We’ll continue to send away samples for testing. … As long as you see the signs (at Upper Dome Lake), it is best to take caution.”
Toxic algae may look like a thick pea soup or spilled paint on the water surface; they might also present as a thick mat or foam along the shore. Learn more about toxic algae at https://tinyurl.com/cdphealgae (link redirects to the Colorado Department of Public Health and Environment’s algae fact sheet.)
Katharhynn Heidelberg is the Montrose Daily Press assistant editor and senior writer. Follow her on Twitter, @kathMDP.