SALISBURY — The Rowan County Environmental Health Department and the Yadkin Riverkeeper are asking High Rock Lake users to take extra precautions after a water sample revealed bacteria in the lake.

The N.C. Department of Health and Human Services and the Department of Environmental Quality investigated a report and confirmed the presence of cyanobacteria on Wednesday.

Cyanobacteria, also known as blue-green algae, blooms in dense mats. They are usually blue-black but turn yellow-green under intense light. It is not considered an invasive species.

Tad Helmstetler, the Rowan County environmental health supervisor, said cyanobacteria is mainly a nuisance but can cause skin irritations and can affect the health of dogs. He said it was not found specifically in the Rowan County side of the lake, which is shared by Davidson and Rowan counties.

He said because the Department of Environmental Quality is unsure if it’s a toxic strand in the lake, it is best to stay away from it and not take a chance.

He recommends avoiding the cyanobacteria mats, which feels like wet cotton, has a bad smell and looks like a blanket spread on the lake.

Edgar Miller, executive director of Yadkin Riverkeeper, said his agency will be going out to High Rock Lake on Friday and meet with state officials Monday to get a better understanding of the impact of the cyanobacteria. He said he’s unsure of the extent of the hazard because it depends on the concentration.

The Department of Health and Human Services recommends safeguarding pets and children from the cyanobacterial blooms by avoiding direct skin contact with the mats and keeping dogs and children from swimming and playing near the growth. The department also advises avoiding water that appears discolored or scummy and not touching large accumulations of algae.

Miller said cyanobacteria is in the same class as a hundred species of blue-green algae that has made dogs ill on the state’s East Coast. He said the toxic version of the algae thrives in brackish and salty water. High Rock Lake is a manmade, freshwater lake.

This is the first reported incidence of the algae in this amount on High Rock Lake, but several other state reservoirs, including Lake Gaston, are actively trying to manage infestations of it. Helmstetler said there are no good theories about what caused the abundance of cyanobacteria to form mats.

Helmstetler said the cyanobacteria mats are typically found in coves and other places where the wind can blow it in and trap it. Mats will not likely be found floating in the middle of the lake. As the weather begins to cool, he says, it will go back to being an occasional nuisance.

Miller said anyone going to High Rock Lake should take precautions, but that cyanobacteria shouldn’t deter people from visiting the lake.

“I don’t want to suggest people shouldn’t get out and enjoy the lake,” Miller said.

Helmstetler agreed, saying lake-goers should check their surroundings and treat the cyanobacteria mats as “bad kids.”

Both Miller and Helmstetler said they will continue to monitor the cyanobacteria and give updates, especially with the upcoming High Rock Lake Clean Sweep scheduled Sept. 21. Helmstetler said the Rowan County Environmental Health Department has a good working relationship with its Davidson County counterpart and will continue to communicate information to the public.