Blue-green algae? Rumors of poisonous blooms probably aren’t true

Salmon Lake is the unfortunate recipient of somewhat polluted water from Seeley Lake. The Seeley Lake sewer and numerous septic systems in the area have caused levels of nutrients, namely nitrogen and phosphorus, to rise downstream in Salmon Lake. (Martin Kidston/Missoula Current)

Montanans should heed reports of blue-green algae infesting lakes, but sometimes the rumors can be inaccurate.

A recent social media report of a woman’s dog dying from being poisoned by blue-green algae in Flathead Lake raised public concerns, but health officials and scientists have their doubts about its truth.

The large lake doesn’t foster some of the conditions that tend to encourage algae blooms, such as shallow depths that allow the water to become warm and stagnant. Still, scientists are checking it out.

“We’ve received some reports (of blue-green algae),” Flathead Lake Biological Station information specialist Ian Withrow told NBC Montana last week. “We’re going to look into the reports; we have someone out there that’s going to take some samples. But we can’t confirm anything yet.”

Confirmed reports of blue-green algae or cyanobacteria killing dogs in North Carolina, Georgia and Texas were shared widely this summer. Some pet owners started becoming more concerned and aware, which may have led to some inaccurate reports in other places.

According to the Montana Department of Public Health and Human Services, blooms usually occur in warm, still water that’s nutrient rich and exposed to sunlight.

“If you see it, I would avoid the water,” said Matthew Ferguson, Montana Department of Public Health and Human Services toxicologist. “When in doubt, stay out.”

Health experts encourage people to avoid swimming in water with blue-green algae simply to be safe. Blue-green algae are toxic only during the narrow window when they’re blooming; however, it’s difficult for people to tell when that’s happening.

Direct skin contact or inhalation of the toxic blue-green algae may cause irritation of the skin, eyes, nose or throat, and people may experience respiratory symptoms after exposure.

Recently, some claim to have seen blue-green algae in Salmon Lake, although that is also unconfirmed. Calls to the Clearwater Resource Council were not returned by press time.

Missoula County Water Quality District supervisor Travis Ross hadn’t heard about algae there, but it wouldn’t be the first time it’s affected Salmon Lake or even Placid Lake.

“That’s happened several times over the past 10 years. It’s pretty common,” Ross said. “It’s come up in discussions of the Seeley Lake sewer.”

Salmon Lake is the unfortunate recipient of somewhat polluted water from Seeley Lake. The Seeley Lake sewer and numerous septic systems in the area have caused levels of nutrients, namely nitrogen and phosphorus, to rise in Seeley and Salmon lakes. 

The lakes warm during the summer and a warm layer of water sits on top of a deep, cold layer. But as fall arrives, the upper layer begins to cool and eventually sinks. This forces the deep layer to the top in a process known as a “turn-over,” and it often brings nutrients up with it, creating prime conditions for algae.

Yes, Georgetown Lake had a fish kill. No, it wasn’t caused by blue-green algae. (Montana FWP)

Meanwhile, over on Georgetown Lake near Anaconda, locals were concerned to see thousands of fingerling trout dead in the shallows near the public boat launch. Some worried that blue-green algae had struck again.

But in this case, it was a fish-stocking problem. 

Montana Fish, Wildlife & Parks technicians had trucked in more than 200,000 rainbow trout to stock the lake last week. But one of the trucks had an equipment failure so not enough oxygen was vented into the water tank.

“The report I got was a good number didn’t make it,” said FWP fisheries manager Pat Saffel. “A few thousand were stressed, but about 30,000 were in good shape. They had a chance of surviving, and some didn’t but some did.”