No current cyanobacteria warnings on Lake Winnipesaukee

LACONIA — Cyanobacteria watches and warnings issued by the New Hampshire Department of Environmental Services last week were removed, leaving Lake Winnipesaukee free from harmful algae blooms for the time being. 

DES issued a cyanobacteria warning for Sunset Lake in Alton and Gilmanton on July 8, and a watch for Lee’s Pond in Moultonborough, but those have since been removed. A warning issued June 14 for Mill Pond in Alton was removed July 9, leaving the Lakes Region free from active warnings and alerts. 

On Lake Winnipesaukee, a warning was issued for the Broads, generally the widest section of the lake, between June 18 and June 26. During the same period, a warning was issued for the Center Harbor area. A warning issued for Center Harbor town beach on June 11 was quickly removed by June 13. And in the Tuftonboro area of the lake, a June 12 warning was removed on June 26. 

Active warnings and watches can be viewed at des.nh.gov/water/healthy-swimming/healthy-swimming-mapper. Suspected blooms can be reported to DES using the form at survey123.arcgis.com/share/151c9fc3c8214c2e93325f77e0f1d578.

Warnings are issued when water sample testing indicates a presence of cyanobacteria in excess of 70,000 cells/mL, between May 15 and Oct. 15. Weekly resampling of affected water bodies is performed when a warning is issued until the detected bloom subsides, according to DES. 

Watches, formerly referred to as “alerts,” are issued when DES conservationists receive photographic evidence of a potential bloom and before they are able to physically sample the water, or when cell counts are approaching the recreational health hazard level of 70,000 cells/mL but have not yet surpassed that figure. A watch could also be issued if a potential bloom was documented but not tested and could recur. Watches sometimes become warnings and can be issued year-round.

Cyanobacteria, commonly referred to as blue-green algae, is naturally present in New Hampshire’s waters but can cause toxic algae blooms that may be harmful to the health of humans and animals. Risks of algae blooms are exacerbated by the introduction of nutrients, including phosphorus and nitrogen, into the ecosystem by fertilizer and other chemical runoff into Lake Winnipesaukee. Heavy rains can wash out roads or sparsely forested areas around the lake and building development can also contribute to the introduction of nutrients to the lake, among other causes. 

Exposure to a bloom could cause acute and chronic health effects, including skin and mucous membrane irritation, tingling, numbness, nausea, vomiting, diarrhea and even seizures, according to DES. 

In June, conservationists received reports of the presence of cyanobacteria in every section of the lake. Waters have since cleared up, for the most part, but the threat of future blooms remains present. The Lake Winnipesaukee Association, a nonprofit organization dedicated to the protection of the lake, will host two public discussions on this topic later this month and at the beginning of August.

The first will be held from 5 to 6 p.m. on Wednesday, July 31, at the Moultonborough Public Library. The second is from 4 to 5 p.m. on Thursday, Aug. 1, at Wolfeboro Town Hall. These programs will cover information on what cyanobacteria are, the risks they pose to human and animal health and the proactive steps the Lake Winnipesaukee Association is taking to combat this threat, according to a press release. 

“This has been an unprecedented start to the summer, with numerous cyanobacteria warnings issued for Lake Winnipesaukee in June,” LWA President Pat Tarpey said in the release. “These talks are a perfect opportunity to understand the concerns, learn why you should care, and learn what steps you can take to lessen the risks associated with these toxic bacteria.”

For more information, visit winnipesaukee.org/lets-talk-about-cyanobacteria.