Harmful algal bloom has a green or blue color / Photo courtesy Charlotte-Mecklenburg Storm Water Services

Nov. 8. By Dave Yochum. The N.C. Dept. of Environmental Quality in late October said people should avoid contact with green or blue water in Lake Norman due to an algal bloom that has lingered since early September.

The bloom has been observed throughout Lake Norman, from Mecklenburg to Catawba, Iredell to Lincoln—algal blooms tend to move due to wind and wave action.

The blooms are a particular species of cyanobacteria called Microcystis which appears as a bright green sheen on the water surface. This species is different from Lyngbya which has been previously observed in similar areas of the lake.

The thing about Microcystis is that it can produce microcystin, an algal toxin that may cause adverse health effects in humans and pets. Samples collected Sept. 18, almost two weeks before Helene, detected microcystin in this bloom, but below concentrations that would exceed public health advisory levels.

Photo: Bob Watson

Monitoring is ongoing, and any new developments will be reported on DWR’s Algal Bloom Dashboard as soon as they are available.

People exposed to small amounts of microcystin toxin experiencing gastrointestinal discomfort or headaches from oral exposure usually recover fully within two days of exposure. Symptoms including rash, skin irritation, or blisters usually subside within one to two weeks of exposure, according to the Iowa Health and Human Services.

Business impact

Jeff Junker, now the owner of Carefree Boat Sales, Docks of Lake Norman and Mountain Creek Marina was born in Cornelius and grew up on Lake Norman and worked at his father’s business, Wher-Rena Boatland for 20 years before selling out around 2018.

Junker

The lake means everything to his businesses, the same for a lakefront restaurant, a boat rental business, a wakeboard store, a custom canvas shop or the fishing tournaments which bring hundreds of visitors to Lake Norman.

“It’s concerning,” Junker says about the cyanobacteria. “It’s currently in areas I’ve never seen before and seems to be spreading from what was initially just the warmer southern-most part of the lake and spreading north. I believe the past two winters are our only years on record without snowfall so we need a big freeze to kill a lot of it off that we just haven’t had in recent years.”

The Microcystis blooms are primarily in coves, hugging the shoreline.

“If it gets bad enough to prevent lake use in summer, that would be catastrophic for the lake life in our area,” he said, referring to swimming and watersports.

The visual indicators that a bloom is present can vary day-to-day—and throughout the day—depending on wind conditions and cloud cover, according to Olivia Edwards, environmental supervisor of LUESA | Charlotte-Mecklenburg Storm Water Services. (LUESA stands for Land Use and Environmental Services Agency.)

“We urge all lake users to avoid contact with green water, blue or brown water. When in doubt, keep out!” —Olivia Edwards on Oct. 24

Microcystis blooms are highly transient. Killing the algal cells with chemical products has been shown to result in a release of toxins into the water increasing the human health risks, Edwards explained. “Chemical treatment is not recommended,” she said.

Junker suggested run-off from Helene could have brought more fertilizer into the lake, encouraging algal blooms. From 2021 to 2023 Cornelius Today reported on 18 sewage spills in Cornelius alone, ranging from 50 gallons on Peninsula Club to 8,000 gallons on Nautique, many of them caused by utility excavation.

“My biggest concern is just how many more areas are affected now than we’ve ever seen before,” he said.

Warmer temperatures 

Warm days with full sun create the ideal conditions for Microcystis to thrive, Edwards said. Thankfully, it’s fall, but it was a warm October.

Edwards

Cyanobacteria blooms usually appear bright green but when a bloom starts to decay, the color can change to a milky blue. Decaying algae may produce a strong, foul odor that can impact a large area.

All that said, there have been no reports of adverse health effects in people or animals. Of course, swimming season ended weeks ago and Edwards said cooler air and water temps will help

“I’m hopeful the cold this winter will kill most of it off but I can’t help but think climate change may mean this is an ongoing issue for Lake Norman,” Junker said.

N.C. Health and Human Services, Division of Public Health (DPH) routinely encourages the public to avoid contact with large accumulations of algae and to prevent children and pets from swimming or ingesting water in an algal bloom.

You can report potential algal bloom concerns within in Lake Norman to NCDEQ’s Algal dashboard here.

How to safeguard against algal blooms

• Keep children and pets away from water that appears bright green, blue, discolored, or scummy.

• Do not handle or touch large mats of algae.

• Avoid handling dead fish that may be present.

• If you come into contact with an algal bloom, wash thoroughly.

• Use clean water to rinse off pets that may have come into contact with an algal bloom.

• If your child appears ill after being in water containing an algal bloom, seek medical care immediately.

• If your pet appears to stumble, stagger, or collapse after being in a pond, lake, or river, seek veterinary care immediately.