From bacteria to harmful algae, warmer waters bring changing risks

A central North Carolina teen recently died from a rare amoeba infection, while two others have died this year from Vibrio bacteria. It's got many people asking: What's in North Carolina's water? On a mild Labor Day morning along the Neuse River, Cynthia Gary and Michael Fennell brought their bikes, but had no plans to get in the water. "The water levels have been very low and the water is extra warm this year because of the high temperatures," Gary said. "I don't think it's a good idea to be out there for me." Fennell said recent reports of waterborne illnesses have made him more cautious. "I see it on the news all the time," he said. "I'm kind of leery of that." Their concern comes after that central North Carolina teenager died last week from a rare infection caused by Naegleria fowleri, an amoeba commonly found in warm freshwater, along with the two deaths this year tied to Vibrio vulnificus, bacteria found naturally in warm coastal waters. The infections are rare and very different. They are also drawing attention to a broader change in North Carolina's waters: As temperatures rise and summerlike heat lasts longer, lakes, rivers and shallow waterways can stay warmer longer, extending favorable conditions for harmful algae and some microorganisms. Warmer water, longer season Shel Winkley, a meteorologist with Climate Central, said prolonged heat can be especially important in shallow or slow-moving waterways. "If we're not seeing water be pushed through our waterways, then that water just kind of sits there," Winkley said. "Especially in more shallow areas, as our atmosphere warms, that allows for these shallower ponds and streams to really start to warm up as well." In Raleigh, the season for summerlike temperatures has lengthened. Winkley found that days reaching about 85 degrees typically ended by early October around 1970. They now extend, on average, until about Oct. 15. That can mean waterways begin warming earlier and remain warm later. Temperature alone does not make water dangerous. Nutrients, rainfall, runoff, sunlight and water movement also influence what grows in it. For harmful algae, those factors can compound. Heavy rainfall can wash nutrients from lawns and farms into waterways. Hot, dry weather that follows can leave warm, slow-moving water where blooms can flourish. "We start the process of warming these bodies of water earlier," Winkley said, giving algae "a longer time frame" to potentially develop. Just before Labor Day, the North Carolina Department of Environmental Quality warned people to avoid discolored or scummy water that could indicate an algal bloom. Some cyanobacteria can produce toxins harmful to people, pets and aquatic life. Most local swimming sites passed recent tests Bacteria are another, more routine water-quality concern, and swimmers generally cannot detect elevated levels simply by looking at the water. Sound Rivers tests more than 50 recreational sites in the Neuse and Tar-Pamlico watersheds during the summer. Its final testing before Labor Day showed most Triangle sites meeting recreational water-quality standards, including the Raleigh and Falls Lake locations tested. One site along the Neuse River at the Neuse Golf Club in Clayton failed the latest test because of elevated bacteria levels. The results also offer important perspective. Warmer conditions can alter water-quality risks, but most local sites tested ahead of Labor Day met recreational standards. That was enough reassurance for Andrea Torrico, who spent the holiday swimming at Raleigh Beach. "I feel like every time I swim in a lake, I hear about the brain-eating amoeba," Torrico said. "But I'm willing to take that risk. It is very rare." The infection is extremely rare, with typically fewer than 10 cases reported nationwide each year. The amoeba itself is much more common and occurs naturally in warm freshwater, including in North Carolina. Infection can occur when contaminated water enters the nose and the amoeba travels to the brain. Vibrio presents a different risk in coastal waters, particularly when contaminated water enters an open wound. Water utilities are preparing, too The effects of warmer water extend beyond recreation. Raleigh Water Assistant Director Ed Buchan said the city's treatment system uses ozone, which helps break down compounds produced by algae that can cause taste and odor problems. "One of the concerns you have is that with warmer climate, more sun, you can have more algae issues," Buchan said. "So we've prepared for that." Buchan said Falls Lake's large volume makes Raleigh's primary water supply less susceptible to some problems that can affect smaller, shallower reservoirs during hot, dry periods. For swimmers, warmer water does not mean North Carolina's lakes and rivers are broadly unsafe. It does mean some risks traditionally associated with the height of summer could remain relevant later in the year as the warm season stretches longer. DEQ recommends avoiding water that is bright green, blue, discolored or scummy and keeping children and pets away from suspected algal blooms. State health officials recommend keeping warm freshwater out of the nose to reduce the already extremely small risk of Naegleria infection. Torrico still plans to make the most of the water while she can. "I love swimming," she said. "What can I say?"