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What to know about blue-green algae blooms in Lake Wylie near Charlotte

 Cyanobacteria, commonly called blue-green algae, is seen in a stillwater pond.
Cyanobacteria, commonly called blue-green algae, is seen in a stillwater pond.

Over the past few months, Mecklenburg County officials have issued warnings about cyanobacteria, commonly called blue-green algae, in Lake Wylie south of Charlotte. The cyanobacteria can produce toxins that are harmful to humans and animals.

Such harmful encounters are rare, though, and have never been reported in the county, said Rusty Rozzelle, the water quality program manager for Charlotte-Mecklenburg Stormwater Services. Still, the county has advised people not to swim in areas where the algae have been spotted.

Here are a few things to know about blue-green algae.

What are blue-green algae?

Cyanobacteria are naturally occurring bacteria found in freshwater, according to the North Carolina Division of Water Resources. They’ve been found in bodies of water throughout the state and use the sun for energy, like plants. When they reproduce rapidly, usually when it’s bright, sunny and warm, they can produce toxins.

“Under most circumstances, the majority of the time, the algae is benign,” Rozzelle said. “It’s just there. And it takes on an almost fluorescent green look. It’s a very bizarre, almost alien-looking color in the water. So it’s pretty easy to see. Most of the time it’s just green, and it’s floating in the water and does not have any toxin associated with it. But for some reason, at an unknown time and at any time, it can produce this toxin.”

The state says cyanobacteria can also appear bright blue, red or brown and will “produce a strong, foul odor and turn milky blue” when they start to die.

How harmful are blue-green algae? 

It depends on whether toxins are being released. So far, there are no documented reports of people being sickened from algal blooms in North Carolina, according to the state Department of Health and Human Services.

“For the most part, it’s benign — not harmful — but it can produce a toxin, and this toxin can be fatal to people and pets,” Rozzelle said.

But because it’s not easy to tell if toxins are being released, the best thing to do is avoid water with blue-green algae entirely.

People who think they’ve touched water containing blue-green algae should wash thoroughly.

The Centers for Disease Control and Prevention says symptoms can depend on how a person or animal was exposed to cyanobacteria. Exposure to the toxins through touching them, swimming through them or breathing them in may lead to skin, eye, nose, throat or lung irritation, according to the CDC. People who swallow contaminated water can have stomach pain, headache, muscle weakness, dizziness, vomiting, diarrhea or liver damage.

Anyone experiencing those symptoms after coming into contact with water that looks like it has blue-green algae should seek medical care. The CDC also advises people who’ve been exposed and are having symptoms to call the poison control center hotline at 1-800-222-1222.

The N.C. Division of Water Resources advises people whose pets start staggering or collapsing after being in a pond, lake or river to get veterinary care right away. Three dogs died after being exposed in eastern North Carolina in 2019, The Charlotte Observer reported.

When was blue-green algae most recently confirmed in Mecklenburg County? 

On Oct. 15, Charlotte-Mecklenburg Stormwater Services found active cyanobacteria blooms in three of the Lake Wylie’s coves — Boyd’s, Snug Harbor and an unnamed one near the Catawba Yacht Club.

The algae have appeared in the Charlotte area for many years, but almost always in ponds, where people aren’t supposed to swim . It’s not uncommon for signs to warn people to keep their pets out of ponds to avoid exposure, even in such traffic-heavy places as Freedom Park last year. But Rozzelle says the county isn’t aware of any confirmed cases of pets dying due to cyanobacteria exposure in Mecklenburg County — or humans, for that matter.

What’s new is that cyanobacteria blooms are being found in the Charlotte area’s lakes, where people are allowed to swim. August was the first time blue-green algae were found in the Mecklenburg County portion of Lake Wylie. Rozzelle says it’s been found in Lake Norman north of Mecklenburg. So far, no blooms have been confirmed in Mountain Island Lake. All three lakes are fed by the Catawba River.

“That makes it doubly important when we start seeing this algae in waters that people swim in,” Rozzelle said.

What’s being done to monitor the blooms?

Water sampling is routinely performed around the county in publicly owned or managed ponds, and Rozzelle says Stormwater Services is checking the afflicted coves on Lake Wylie on a weekly basis. The county encourages people who have ponds on their land to reach out to pond management consultants if they have concerns about blue-green algae.

When blooms are confirmed, the county advises people to stay out of the water and keep their pets on land. It’s best if people don’t pick up any dead fish they see in the area and avoid fishing in areas that appear to have a blue-green algae bloom. Signs are generally put up to notify people about the risks.

“We advise people that if you are fishing, be sure to wash your fish very well and wash your hands after contacting the fish if you see the presence of bright green color because the water on the fish could carry the toxin as well,” Rozzelle said.

Mecklenburg County will issue public notices when it confirms the presence of harmful algal blooms as well as when the blooms subside.

Still, Rozzelle says, it’s best for people to be aware of their surroundings.

“Don’t rely on the government to tell you when the water’s safe, because we can’t be everywhere all the time,” Rozzelle said. “This cyanobacteria can be present and not produce toxins. It can be present and produce toxins … If you see that bright green, fluorescent color in the water, then stay out of the water.”

You can find more information out here from Charlotte-Mecklenburg Stormwater Services, here from NCDHHS and here from the CDC.

If you see what you think is a blue-green algae bloom, contact the local North Carolina Department of Environmental Quality office.

Copyright 2021 WFAE

Dash joined WFAE as a digital editor for news and engagement in 2019. Before that, he was a reporter for the Savannah Morning News in Georgia and the Gaston Gazette in Gastonia.