It’s peak season for cyanobacteria blooms: the blue-green algae that sprouts in bodies of water, which can be harmful for humans and animals.
As of July 15, there are two active cyanobacteria advisories on New Hampshire waters, at Keyser Pond in Henniker and Silver Lake Beach in Hollis.
As summers get warmer with a changing climate, those blooms have more of a chance to thrive, said University of New Hampshire professor emeritus Jim Haney.
“There are larger blooms now, because with the warmer water, this gives an advantage to the cyanobacteria that have an optimal temperature several degrees higher than most of the other plankton,” he said.
While it’s not unusual to see cyanobacteria activity this time of year, Haney said “what’s less normal is the number of lakes that are displaying these blooms, and especially lakes that in the past have not had blooms.” Warmer weather has also extended the season for cyanobacteria blooms, he said.
And changing weather patterns, including heavier rains and more periods of drought, cause more nutrients to run off into water bodies. In turn, that helps the bacteria grow.
“What’s happening is New Hampshire is getting wetter,” said NH Lakes President Andrea LaMoreaux. “We’re getting more rain, but we’re getting it in fewer storms, which means our storms are bigger. And when we have bigger storms, we have more pollution running off of the landscape.”
This is a concern, she said, because of the pollution that can run off into lakes.
Impacts across New Hampshire
In New Hampshire, the cyanobacteria season has been off to a busy start, with some of the early blooms even occurring in public water supplies in Salem and Lebanon.
State regulators say reported sightings of the blooms have increased. Ted Diers, assistant manager of the water division at the Department of Environmental Services, said it is difficult to determine if there are more blooms or if Granite Staters are getting better at recognizing and reporting them.
Monitoring blooms is a challenge, Diers said, because blooms are episodic. With blooms lasting longer into the season, it’s still hard to predict where and when they’ll occur.
The department doesn’t have a good sense for what long-term cyanobacteria populations look like in most of the state’s lakes.
The bacteria tend to collect at the bottom of lakes, Diers said. But when they move towards the surface — fed by sunlight and nutrients — their populations explode, causing a bloom.
“There’s a lot of factors that go into a bloom, including the surface conditions, wind, certainly temperature of the lake,” Diers said.
Rain can sometimes make blooms better or cause blooms to happen.
There are about 12 different species of the bacteria across New Hampshire, and they can all have different presentations. Some look like an oil slick on top of the water, but the typical presentation is a blue-green splotch.
“It looks like somebody sort of spilled some blue-green paint in the water and it’s swirling around, kind of like the backdrop to a seventies psychedelic video,” he said. “But it can just be big blobs of nastiness.”
His advice to those spending time near local lakes, ponds or other waters?
“If it looks gross, don’t swim in it,” he said. “Don’t let your pet near it.”
Effects of cyanobacteria
Cyanobacteria blooms can cause harmful health effects in humans and in animals.
Some blooms produce cyanotoxins, which can cause symptoms ranging from abdominal pain and headaches, to numbness and speech disturbances, according to the Centers for Disease Control and Prevention.
Exposure generally happens when someone ingests, touches or breathes in the toxins. The toxin can also get into people’s eyes.
Right now, Haney’s research at UNH is focusing on how those toxins can move through the air.
“We’re finding some very exciting and alarming things,” he said. “Many of the toxins that are produced by these cyanobacteria in the lake actually can emerge from the lake in the form of aerosols and be transported to other locations.”
Going forward, researchers are looking into how long the toxins can stay in the atmosphere, how far they can move, and whether they could affect communities living near bodies of water with blooms.