The cost of cyanobacteria

Funds are running low in the fight against toxic bacteria in New Hampshire’s ponds and lakes. But the number of projects undertaken so far pales in comparison to what officials say is still needed to restore and protect the state’s water bodies. 

With a proposal for a cyanobacteria funding task force headed to the governor’s desk, here’s a look at what has already been done to combat the problem and what experts say is needed to keep the state’s lakes clear and safe.

Swirling, green, and costly

The first reports of cyanobacteria blooms in New Hampshire occurred in the 1960s, according to Amy Smagula, New Hampshire Department of Environmental Services chief aquatic biologist and director of the center for limnology, the study of inland aquatic ecosystems. Since that time, she said in an interview, there have been upwards of 400 bloom incidents recorded across New Hampshire’s approximately 1,000 lakes and ponds.

Cyanobacteria are microscopic organisms that thrive in warm, nutrient-rich water. When conditions are right, they proliferate, amassing in high concentrations known as blooms. Certain types of cyanobacteria produce toxins with effects from nausea and headaches to life-threatening poisoning, according to the U.S. Environmental Protection Agency.

The New Hampshire Department of Environmental Services, along with lake associations, land trusts, and others, has embarked on a range of projects to combat the problem, which is worsened by development, fertilizer runoff, and climate change.

Erosion and stormwater runoff can be managed to minimize the flow of sediments and nutrients, which feed cyanobacteria, into lakes, Smagula said; this might take the form of road and stormwater infrastructure improvements or planting trees and other vegetation along roads and water bodies.

There’s also the option of chemical treatment, which the department generally considers a last resort, Smagula said. After years or decades of efforts to treat upstream causes, a handful of New Hampshire lakes have undergone this option, which typically costs hundreds of thousands of dollars and which biologists do not consider a permanent solution. 

How much has all this cost? In 2023, the Legislature allocated $1 million to the Cyanobateria Mitigation Loan and Grant Fund, which was later bolstered with another $1 million in American Rescue Plan Act funding. 

But that isn’t the whole picture. Municipalities and lake associations provide varying amounts of matching funds to access loan and grant dollars. And upstream of that phase, to apply they must show a “watershed-based plan,” which is a comprehensive assessment of the unique conditions in their lake’s ecosystem that helps the Department of Environmental Services have confidence the treatment will be effective. Putting these plans together can cost in the neighborhood of $100,000. 

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Meanwhile, other funding sources, including federal grants, have provided additional funding for New Hampshire cyanobacteria mitigation projects as well over that period. 

The $2 million in the Cyanobacteria Mitigation Loan and Grant Fund has paid for 11 projects since 2023, leaving the fund with about $200,000 left as of April 2026, according to Smagula, who administers it. 

That “won’t fund a whole lot of projects,” Smagula said. 

Meanwhile, cyanobacteria blooms aren’t abating. About 60 to 70 water bodies in the state deal with a bloom each year, and half of those tend to be toxic, she said at a hearing before the House Committee on Resources, Recreation, and Development in March. Blooms may last anywhere from a day or two to months.

Some of the factors that aggravate blooms are worsening with time. Development increases the human toll on lakes from road, fertilizer, and septic runoff. Climate change warms water bodies, concentrates nutrients in times of drought, and increases the frequency of severe storm events, which wash sediments and nutrients into lakes and ponds. The introduction of invasive species and decline in native insect populations can be factors in blooms, too, scientists say.

Over multiple decades with NHDES, Smagula said she had observed more blooms recorded on average each year and more diversity of cyanobacteria species appearing in New Hampshire’s waters. Together, those factors indicate that the problem is growing in scale, she said.

“It’s not just that more people are looking. There actually are more blooms,” she said.

Task force may form this summer, pending Ayotte’s signature

On Thursday, April 9, the House passed Senate Bill 598 by voice vote. The bill proposes a task force to evaluate different potential funding streams to bolster the cyanobacteria mitigation fund, from a decal sticker for recreational boats to a special license plate and others. The task force would also consider establishing a program through the Department of Transportation to evaluate improvements to road infrastructure that could reduce the amount of stormwater flowing into lakes and ponds.

Another bill proposing a method of bolstering the fund is House Bill 1477, which suggests a registration fee for “seasonal floating platforms,” or rafts. The proposal, which calls for a fee of $50 to be split between the cyanobacteria and navigation safety funds, passed the House in February and is now before the Senate.

Diversifying the sources that feed the fund will be crucial to the state’s ability to continue with mitigation projects, Smagula said. New Hampshire is known for the beauty and clarity of its water, she said, so continuing those projects will be important both for the future of the state’s tourism economy and the health and well-being of its residents, pets, and wildlife.