The late season cyanobacteria bloom that was discovered on Lake Nubanusit in Hancock is a cause for monitoring, not panic, Department of Environmental Services public beach coordinator Amanda McQuaid said.
Locals grabbed a sample of cyanobacteria from the lake on Nov. 10 and documented a surface bloom near the northeast corner of the lake. There may also have been cyanobacteria in nearby Spoonwood Pond at the time as well, McQuaid said. Cyanobacteria can be harmful to people and animals if they ingest it.
The high temperatures in early November caused several cyanobacteria blooms across the state, she said, a “perfectly natural” occurrence given the abnormally hot, dry summer and the warm temperatures during fall lake mixing and turnover, where nutrients from the bottom of lakes travel up through the water column, she said. It’s not necessarily an indication that the notoriously clean and clear Lake Nubanusit has a nutrient problem, she said.
In terms of public health, it’s hard to say what kind of a risk remains, McQuaid said. “The surface bloom is likely gone,” she said, since the weather’s been colder and rainier since the bloom, but no official cell count or resampling occurred after the DES issued an alert, in part because there were so many blooms reported across the state at once.
Although it’s late for swimming season and Nubanusit Lake doesn’t have many houses or opportunities for bathing, visitors to any lake should still be on the lookout for surface scum, water that changes colors, or appears to have green streaks or blue-green flecks aggregating along the shore, McQuade said, and keep their dogs from swimming or drinking the water if they see anything that could be cyanobacteria. “In any situation, don’t use lake water for drinking,” she said, and lakeside residents should avoid using lake water for showering or dish washing during an active cyanobacteria bloom. Many of Nubanusit’s residents are gone for the season, she said.
This fall’s bloom isn’t a guarantee that another bloom will occur next summer, McQuade said. “Weather patterns play a big role in how it surfaces,” she said, and blooms can occur from long-term nutrient build-up without any active pollution events. However, this bloom does serve as a reminder that the clean and clear lake is still vulnerable to blooms, she said. Stewards of waterfront properties should still employ best practices, such as monitoring fertilizer and detergent use, or impacts from beach sand and development.
Cyanobacteria are commonly found in water bodies and can bloom or create surface scum when excess nutrients are in the water. Some forms of the bacteria can be toxic and cause acute and chronic health impacts, which can range in severity. Acute health effects include irritation of skin and mucous membranes, tingling, numbness, nausea, vomiting, seizures and diarrhea. Chronic effects may include liver and central nervous system damage. During times of high cyanobacteria concentrations, residents are advised to keep out of the water and not allow their pets to drink or swim in it.
Visit the NHDES Beach Program website for photos and more information about cyanobacteria.