Clear waters in Moultonborough’s Lake Kanasatka this summer have strengthened residents’ hopes that an expensive, last-ditch chemical treatment applied in 2024 is successfully controlling recurrent cyanobacteria blooms. While the $600,000 intervention has dramatically suppressed phosphorus levels and restored a healthy local food web, experts emphasize that the method is not a permanent fix nor a universal solution for all regional water bodies.
In Plain English: The Clinical Takeaway
- What Was Done: An alum treatment was applied to Lake Kanasatka in 2024 to chemically bind and neutralize excess phosphorus on the lake bed.
- Biological Impact: By locking away the nutrient source that feeds cyanobacteria, water clarity has improved drastically, allowing local fish, loons, and zooplankton populations to rebound.
- Public Health Caveat: This intervention targets specific nutrient overloads in individual lakes and carries a high financial cost, meaning it cannot be universally applied across every body of water facing algal blooms.
Restoring Lake Kanasatka After Years of Severe Blooms
This year has marked a distinctly positive season for Lake Kanasatka, according to waterfront resident Kevin Kelly, who noted that conditions have steadily improved each year since the treatment was applied in 2024. Those improvements follow a period of intense public anxiety and health concerns regarding recurrent cyanobacteria blooms that peaked dramatically the year before.
Amanda McQuaid, director of the UNH Lakes Lay Monitoring Program, stated by the shore that the intervention is performing precisely as intended. The contrast with prior seasons is stark. McQuaid recalled that during the summer of 2020, the color of the lake water closely resembled Gatorade, culminating in 2023 when the water body suffered through blooms worse than any previously documented at the site. The thick, green, scummy water eventually spilled over into neighboring Lake Winnipesaukee, to which Kanasatka is linked.
The Mechanism of Alum Treatment and Ecosystem Recovery
Cyanobacteria blooms materialize when bacteria naturally present in water bodies at low concentrations begin to grow unchecked, fueled by rising temperatures linked to climate change and excessive nutrients like erosion or fertilizer runoff. These blooms frequently generate toxins capable of harming humans and animals alike. To combat this on Lake Kanasatka, the Lake Kanasatka Watershed Association pursued a chemical intervention involving the deposition of alum into the water.
When introduced, alum binds directly with the nutrient phosphorus and settles to the lake floor, preventing the nutrient from feeding new bacterial growth. Scientists anticipate this chemical lockdown will remain effective for at least a decade, according to McQuaid. Although the decision felt risky to community members concerned about introducing chemical agents into a treasured environment—with Kirk Meloney, who at the time was leading the Lake Kanasatka Watershed Association as its president, noting his initial hesitation before choosing to follow the science—the results have proven stabilizing.
While minor cyanobacteria blips still occur following heavy rainstorms that wash nutrient-laden runoff into the lake, overall phosphorus levels remain a fraction of their pre-treatment measurements. Fieldwork conducted by McQuaid’s team, which brought up water teeming with typical algae and active zooplankton using a cone-shaped net, points to a revitalized local food web supporting fish and local loons.
Financial Hurdles and Limitations Across Regional Waters
Experts emphasize that the alum treatment is only part of the explanation for Lake Kanasatka’s recovery. Milder summer rainstorms and heightened preventative work by local residents—such as improved stormwater management on properties and nearby roads—have also played significant roles, alongside a general regional decrease in bloom severity this year.
McQuaid cautioned that the treatment is not a universal fix. Alum targets accumulated nutrient overloads rather than the cyanobacteria itself. It also demands substantial financial backing. Lake Kanasatka’s treatment required approximately $600,000, partially defrayed by a $500,000 state grant that halved the million dollars initially allocated by the Legislature to the Cyanobacteria Mitigation Loan and Grand Fund in 2023. As of fall 2026, the fund’s balance dropped to roughly $200,000 after subsequent legislative attempts to replenish it were voted down or sent to study committees.
| Metric / Factor | Pre-Treatment (2020–2023) | Post-Treatment (2024–2026) |
|---|---|---|
| Water Appearance | Gatorade-colored, thick green scum | Clear, “beautiful” conditions |
| Phosphorus Levels | Elevated baseline fueling unchecked blooms | Reduced to a fraction of prior levels |
| Treatment Cost | N/A | Approx. $600,000 total investment |
Contraindications & When to Consult a Doctor
Because cyanobacteria can produce toxins harmful to both humans and animals, exposure through recreational water use poses legitimate health risks.
References
- New Hampshire Bulletin / New Hampshire Public Radio (NHPR) original reporting archives.
- University of New Hampshire (UNH) Lakes Lay Monitoring Program field reports.
- New Hampshire Cyanobacteria Mitigation Loan and Grand Fund legislative tracking data.
