How to spot dangerous blue-green algae

Published: Sep. 18, 2018 at 4:15 PM EDT
Email This Link
Share on Pinterest
Share on LinkedIn

July has already been several degrees above normal and that's great for warming up the water for swimming. But that also could lead to dangerous blue-green algae growth.

Several sites are now on "high alert" status for blue-green algae including in Franklin, Chittenden and Addison counties. And on the New York side, in Clinton and Essex counties. That means someone spotted dense scums or highly colored water that's not safe to go in.

So do you know how to tell the difference between dangerous blue-green algae and harmless algae? Our Cat Viglienzoni asked the experts.

It's been a hot month. And with the extra heat, the health department is concerned about toxic cyanobacteria or blue-green algae growing in Lake Champlain because the algae loves these hot temperatures.

"Given the heat wave, I don't think it's as bad as I may have been expecting," said Bridget O'Brien, a toxicological and radiological analyst with the Vt. Department of Health.

That's because the water is still a bit too cold for blue-green algae to flourish. The health department says the algae likes water temperatures in the mid-upper 70s and higher, whereas the lake water is still 71 degrees. That's why the health department says we usually see blooms later in the later summer, like August and early September.

"We're all sort of literally on pins and needles waiting for it to come," said Phelan Fretz, the executive director of the ECHO Leahy Center.

Fretz has an office overlooking the beginnings of a potential bloom behind ECHO.

"We're starting to see a significant increase in two things: the size of the blooms and, also, how early they come in the season," Fretz said.

To be clear, Fretz says blue-green algae is normal. The problem comes when, because of higher temperatures and nutrient load, it outcompetes the other algaes and forms a bloom. That bloom can then produce toxins that the health department says can make you or your pets sick.

"You could experience skin rashes or allergy-like symptoms. And then if you swallow water with high levels of toxins, you could experience stomach issues like cramping or vomiting or diarrhea," O'Brien said.

They say a lot of people incorrectly report blue-green algae.

Fretz explained the difference: "There's going to be algae growing off the rocks-- that's not blue-green algae. You might see some milfoil or other plants growing up from the bottom, sort of stalk-like with leaves-- they're not blue-green algae. This is literally an algae that is a micro-organism."

So if you can pick it up with a stick, it isn't blue-green algae. If it has leaves, it's likely duckweed or another plant. And if it's yellow and you also see it on the ground, it's probably just pollen.

Instead, look for bluish-green dots, a pea soup consistency and an oily sheen, which is part of the algae's toxic output.

Include where you saw it and a photo so they can verify that what you're seeing is, in fact, blue-green algae. If possible, include a detailed description of the bloom's location, or mark the bloom location using an image from an online mapping application such as Google, Bing or Yahoo Maps.