Lake Winnipesaukee’s Under Siege By Cyanobacteria

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Meredith—June 25, 2024—The 72-square mile crown jewel of the Lakes Region, Lake Winnipesaukee, is under siege right now from cyanobacteria reports from beaches and bays from Gilford, Meredith, Center Harbor Tuftonboro and Moultonborough.

David Neils, chief aquatic biologist for the state Department of Environmental Services, said these are not closures of the water, but warnings issued against swimming or wading in places where thick blue-green masses are present as they can produce a toxin which can cause illness to people, pets and wildlife. He said this is a particularly bad year on the big lake as it did not freeze for very long this winter and there has been a lot of heat and nutrient load added.

“It’s dynamic,” Neils said noting blooms in the water can move, drop lower in the water below the surface and can dissipate particularly after a rainstorm.

The warning signs were posted for the first time in at least seven years in Center Harbor and the signs were also up in Meredith at the Town Docks and boat landing where dogs often go for walks and swim.

Also in Gilford, around Governor’s Island, warnings were issued and even the deep area of water in The Broads in addition to warnings issued previously this month for Tuftonboro and Wolfeboro.

The state has issued current cyanobacteria warnings for 12 areas in the state, six of which are on the Big Lake. The state’s healthy swimming map is here

This blue-green algae which looks like thick green scum and recently has been seen with yellow pollen floating on the top, can make pets sick that drink it and potentially cause neurological damage in people who swim in it.

Warnings are issued when samples are above 70,000 cells/ml and at 19 Mile Beach in Tuftonboro, the counts were 561,000 cells/ml and at Carry Beach also on the Tuftonboro side, 160,000 cells/ml wrote Bree Rossiter, conservation project manager for the Lake Winnipesaukee Association in a posting on the Winnipesaukee Forum

Those who participate in a talk forum on the page have been active with about 100 cyanobacteria-related posts, with people blaming those who fertilize lawns near the lake and the Canada geese, who flock to the region in large numbers, largely attracted by lawns.

Meredith’s Hesky Park’s lawns and walkways are dotted with green feces of the geese right now and the geese themselves can expel on average two pounds of waste a day, adding to the load.

Much of the cyanobacteria – which is naturally occurring – comes from surface water runoff from the roads, parking lots and culverts which enter the water body.

Kate Hastings of the New Hampshire Department of Environmental Services is asking anyone who sees green blooms to stay away, photograph the material and upload it to the department to be analyzed. The link for reporting is here

In addition to the six sites all around the northern half of the lake, there are current cyanobacteria warnings (advisories) for Pleasant Lake in New London, Mascoma Lake in Enfield, Swain’s Lake in Barrington, Province Lake in Effingham/Wakefield and Mill Pond in Alton.

Andrea LaMoreaux of the NH Lakes Association said the season got off to a very bad start for cyanobacteria early. She said New Hampshire lakes have seen a record number of toxic cyanobacteria blooms for the past four years.

In addition to the locations already mentioned, blooms were discovered Tuesday near Center Harbor Town Beach, at Moultonborough Town Beach and in the Broads.

Also under advisories against going into the water are currently at Leavitt Park, Salmon Meadow Cove, and between Avery and Cook’s Point, Hermit Cove, Bear Island, Cook’s Point and Long Island, Springfield Point, Barndoor Island, near Blaisdell Point, Brewster Beach.

These locations have red signs posted right now with warnings for people and pets to stay out of the water.


  1. Cynthia B. 4 weeks ago June 26, 2024

    I visited a hardware/plant store last week on Rt 16 in Ossipee. One of the workers there told me “yup, I shouldn’t tell you this, but most of our bagged fertilizer is from Russia and it has human excrement in them.” It’s not all about climate change – the shore lines are bereft of natural buffers, they are fragmented, and home owners continue to collectively ply tons of fertilizer on their green lawns.

  2. Deb 4 weeks ago June 26, 2024

    I have never understood people planting lawns near our beautiful and fresh water lakes. I also have never understood why it was allowed. Of course people that plant lawns are going to use all these chemicals to keep it looking nice. It pains me when i see them I remember being in line at the hardware store in Ossipee and someone was buying fertilizer and the salesperson said to them you do know you can not fertilize within so many feet of the lake? , I cant remember what the footage was but i was so happy to hear him address it. Although i wondered if it really would make a difference, especially in these big rains we are having and it will only continue to get worse according to future projections and climate change.

  3. Allen Wrench 4 weeks ago June 27, 2024

    Alot of these areas with warnings have been lifted. The lake is clearing up again. These articles are over the top and making people crazy. So many kooks asking if it’s safe to swim in the lake. Lake Winnipesaukee is huge. A few closed beaches early on and new articles telling people to stay out of the water. What buffoonery. 90% of the lake was still swimmable. Stop putting fear in people.


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