Metro Parks has posted signs around Lake Watauga in Centennial Park warning visitors to avoid contact with the water and to keep pets away, after the Tennessee Department of Environment and Conservation notified officials that a cyanobacterial bloom had been observed in the lake. Metro Parks conducted water sampling on Thursday, September 24, 2026, to determine whether the bloom had produced toxic algae, with laboratory results expected next week.
State Notification Triggers Testing and Signage
Metro Parks confirmed it conducted water sampling at Lake Watauga on Thursday, September 24, 2026, to test for the potential presence of toxic algae, according to WKRN News 2. The testing follows notice from TDEC that a bloom had been spotted in the lake, and officials say they will provide an update once lab results come back. The visible bloom prompted a precautionary response that included water sampling.
The signs now posted at the lake advise visitors to avoid contact with the water and to keep pets away from it, and Metro Parks is encouraging both visitors and their animals to steer clear until more is known. Pets may be exposed by drinking contaminated lake water or licking toxins from their fur after swimming. Severe neurological or hepatic symptoms in dogs can appear within minutes to hours of exposure, per the same guidance.
Health Risks for People Who Come Into Contact With the Water
For human visitors, exposure can also pose health risks. Metro Parks is testing Lake Watauga after a cyanobacteria bloom was observed. Cyanotoxins tend to spike when cyanobacteria blooms begin dying off or reach high concentrations, which is part of why officials are treating any visible bloom as a precaution worth testing immediately.
This is not the lake's first rough patch this year. Visitors reported a foul odor around a lake at Centennial Park, and Metro Parks said it knew the cause, as WSMV 4 reported. Metro Parks says all four turbulators are now working and that the lake is chemically treated on a regular basis, though warm late-summer temperatures and nutrient runoff can still set off cyanobacterial blooms even with that equipment functioning.
Built-In Defenses Against Algae in a Century-Old Lake
Lake Watauga isn't without built-in defenses against algae growth. The lake includes vegetated floating wetland islands designed to absorb phosphorus; the surface area of a 250-square-foot island is comparable to a full acre of natural wetlands, according to the Centennial Park Conservancy. The lake also has a turbulator system, with all four units now working, according to Metro Parks.
Those tools build on a larger investment in the lake's water quality. A $9 million Phase 1 restoration of Centennial Park completed in 2015 daylighted the long-buried Cockrill Spring, whose water is pumped to Lake Watauga, according to the city's parks department. Lake Watauga itself dates back to the 1897 Tennessee Centennial Exposition, when it was built as an artificial centerpiece for the fair, and it takes its name from an 18th-century pioneer settlement along East Tennessee's Watauga River, per Wikipedia.
A Recurring Problem Across Tennessee's Lakes
Nashville is far from alone in dealing with this issue. A cyanobacterial health advisory was issued at Mead's Quarry Lake in Knoxville in March 2024, where UT Knoxville students took samples and further analysis by Ijams and the Tennessee Department of Health and TDEC confirmed microcystin toxin levels as high as 28 micrograms per liter, well above the 8 microgram-per-liter health threshold, according to Newsweek. At the time, an Ijams official said warming temperatures could contribute to a recurrence of that bloom.
Centennial Park sits in Nashville's West End along 25th Avenue North and draws an estimated two million visitors a year, according to the Centennial Park Conservancy. The park includes Lake Watauga and the Parthenon. That kind of foot traffic means any lake closure or advisory reaches a wide swath of the city. For now, Metro Parks says the signs stay up and officials are awaiting lab results, with an update promised next week.
