Swimming in water with too much cyanobacteria can cause rashes, fevers, headaches, mouth blisters, vomiting, acute liver damage, according to DES. Here, a bloom on Phillips Pond in Sandown in 2021. The pond currently is on a cyanobacteria watch. (Courtesy of the New Hampshire Department of Environmental Services)
With Labor Day weekend approaching, more than a dozen beaches around the state had active notices Monday for types of bacteria that can pose serious health risks.
From late May to early September, New Hampshire’s Beach Inspection Program monitors public beaches for fecal bacteria. And with reports from residents, the state also tracks cyanobacteria blooms, growths that can be dangerous to humans and pets.
As of Monday afternoon, 17 beaches around the state had active notices for cyanobacteria or fecal bacteria, including Lake Winnipesaukee. These beaches aren’t closed, but state officials advise residents to avoid or act with caution around these waters. Up-to-date information can be found on an online tool maintained by the Department of Environmental Services called the Healthy Swimming Mapper .
Residents should note that beaches may still have hazards even if they don’t have active notices. Beaches aren’t tested daily, and the state relies on resident reports of potential cyanobacteria blooms, which can be done through an online form .
These bacteria can be dangerous. Cyanobacteria — which thrive in warm, sunny, nutrient-rich environments — are often toxic. They can cause rashes, fevers, headaches, mouth blisters, vomiting, acute liver damage, and more, according to DES . They can sometimes lead to neurological issues like numbness and seizures.
These blooms are expected to become more common with climate change-driven warming. They can be blue, green, yellow, white, or brown and look like spilled paint, scum, or blotches.
Fecal bacteria pose risks, too. They can bring on nausea, vomiting, respiratory illness, and infection, according to the U.S. Environmental Protection Agency .
Four beaches had fecal bacteria advisories as of Monday afternoon. An advisory for fecal bacteria is issued when a water sample contains “levels that exceed the state standard, indicating unhealthy swimming conditions,” according to DES. The following places were flagged:
- Corcoran’s Pond Beach in Waterville Valley since Aug. 20
- North Hampton State Park Beach since Aug. 21
- Troy Town Beach since Aug. 22
- Seabrook Harbor Beach since Aug. 23
Three beaches had cyanobacteria watches, also called alerts. Alerts mean residents should “be on the watch” for a potential bloom, according to DES. These places had alerts as of the start of the week:
- The Alton area of Lake Winnipesaukee since Aug. 19
- Phillips Pond in Sandon since Aug. 22
- Locke Lake in Barnstead since Aug. 23
More serious are cyanobacteria warnings, which mean that cyanobacteria have been found at a concentration where harmful toxins could be present and threaten public health. Ten beaches had warnings on Monday afternoon:
- Province Lake in Effingham and Wakefield since Aug. 2
- Baboosic Lake in Amherst since Aug. 5
- Halfmoon Pond in Kingston since Aug. 8
- Tucker Pond in Salisbury since Aug. 15
- The Wolfeboro area of Lake Winnipesaukee since Aug. 19
- The Tuftonboro area of Lake Winnipesaukee since Aug. 20
- Showell Pond in Sandown since Aug. 21
- Arlington Mill Reservoir in Salem since Aug. 22
- Keyser Pond in Henniker since Aug. 23
- Lake Monomonac in Rindge since Aug. 23
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