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NH on track to set new record for cyanobacteria blooms

 An algal bloom in a body of water
Courtesy of New Hampshire Department of Environmental Services
An algal bloom in a body of water

This year is projected to see the highest number of cyanobacteria blooms ever reported in New Hampshire, according to data from the New Hampshire Department of Environmental Services.

Kate Hastings, who monitors cyanobacteria blooms for the state, said cyanobacteria has already passed a number of other records this summer alone.

“We'll see how the rest of the year plays out, but we have broken the record for the total number of advisories recorded within each month so far this year,” she said. “In addition to setting the record for the most advisories ever issued within one month. That was set this past June.”

Cyanobacteria are photosynthetic microorganisms that can be found in many aquatic environments, including New Hampshire’s lakes. They are known for taking advantage of ecosystem irregularities; when the conditions are right, cyanobacteria can spread across the surface of a pond or lake, covering the water with a green, algae-like film.

While the increase in reports can partially be attributed to increased awareness, Hastings said, there are two additional contributing factors: an uptick in development around water bodies and the impact of climate change. That includes the severe rainstorms we’ve been seeing this summer.

“These huge storms bring in big pulses of nutrients all at once, instead of a more regular input of lower nutrients spread out over the duration of the summer,” said Hastings.

Other changes, such as less ice cover on many lakes in winter and higher temperatures than normal, can also spur blooms.

Cyanobacteria in high densities have the potential to release cyanotoxins. Exposure to these toxins can cause mild to severe health side effects in humans and pets.

The state environmental agency recommends avoiding bodies of water that have active cyanobacteria advisories or alerts.

Hastings said people should report any suspicious discoloration in local lakes and ponds to the state environmental agency so they can perform testing.

You can find reference photos of cyanobacteria blooms, as well as a reporting form here.

To view active cyanobacteria alerts and advisories, visit the state’s Healthy Swimming Mapper

Adriana (she/they) was a news intern in the summer of 2023, reporting on environment, energy and climate news as part of By Degrees. They graduated from Northwestern's Medill School of Journalism in June 2023.