First Cyanobacteria Warnings of 2024 Issued for Lake Winnipesaukee

[Lake Winnipesaukee Alliance]

Yesterday, the New Hampshire Department of Environmental Services (NHDES) issued the first Cyanobacteria Warnings (previously Advisories) on Lake Winnipesaukee for 2024. The initial total cyanobacteria density for the sample collected at Nineteen Mile Beach was 561,000 cells/mL and density for Carry Beach was 160,000 cells/mL. Warnings are implemented when cell counts exceed 70,000 cells/mL. The taxa Dolichospermum was identified in both samples, and Aphanothece was also found in the Nineteen Mile Bay sample.

To stay up to date on these warnings, I highly suggest that you sign up for NHDES Waterbody Specific Notifications. You can check the status of the warnings and alerts using the Healthy Swimming Mapper. We will be updating the LWA Cyanobacteria page and tracking map this week. If you suspect a bloom, please use the NHDES Reporting Tool and contact LWA. The blooms in Wolfeboro are described as "thick green material mixed with swirls of yellow pollen along the shoreline." The Tuftonboro blooms are described as "green clouds thoroughly mixed into the water on the shoreline." All samples had pollen mixed in. Any surface scum should be avoided, especially if the material is green.


There are numerous factors that play into when and where cyanobacteria blooms occur and it is almost impossible to point directly to one source. Cyanobacteria feed on nutrients and sunlight. Limited ice in, fertilizer use, polluted stormwater runoff, erosion, and failing septic systems are just a few of these factors. Less ice = more sunlight, more sunlight = increased plant/algae growth.

How can you help? LWA works on Watershed Management Plans throughout the watershed by Bay, identifying sites in need of remediation (failing culverts, lacking vegetation, poor maintenance etc.) on public property. Private property owners can do their part to adopt Lake-Friendly practices like retrofitting drains that empty directly into the lake, taking proper care of their septic systems, stopping fertilizer usage (especially those containing phosphates), pick up their pet waste, break up their lawn with native plantings, and designate walking paths to minimize soil compaction that leads to erosion. Please visit www.winnipesaukee.org for more info on how you can do your part to minimize excessive nutrients from entering the lake.


Stay safe!
Bree Rossiter
Conservation Program Manager