No cyanobacteria watches, warnings on Lake Winnipesaukee ahead of Labor Day weekend

There weren’t any cyanobacteria watches or warnings on Lake Winnipesaukee on Thursday afternoon ahead of the busy Labor Day weekend. 

Though there weren’t any watches or warnings, individual reports of cyanobacteria blooms remained on Lake Winnipesaukee in the area of Moultonborough Neck and Long Island. 

One of those, observed on July 22, appeared heavier deeper down in the water column and looked something like a snow globe. A sample collected the same day indicated the presence of stigonema at a density too numerous to count.

Viewing the New Hampshire Department of Environmental Services Healthy Swimming Mapper, red triangles indicate a sample has been collected and cyanobacteria density exceeded 70,000 cells per mL. Orange triangles indicate a sample was collected, and cyanobacteria density did not exceed 70,000 cells per mL. Black triangles indicate instances where a report was made with a photograph, but no sample was collected.

In the area of Moultonborough Neck and Long Island, there are three red triangle reports, indicating cyanobacteria densities in excess of 70,000 cells per mL, the state standard.

View the Healthy Swimming Mapper by navigating to des.nh.gov/water/healthy-swimming/healthy-swimming-mapper.

Two other locations, sampled on Aug. 13, also resembled a snow globe and appeared heavier deeper down in the water column. Both of those were tested and identified to be benthic cyanobacteria, the density being too numerous to count.

On Mirror Lake near Tuftonboro Neck, a cyanobacteria bloom reported Aug. 25 was tested and the results showed dolichospermum, woronichinia and microcystis mixed with iron bacteria at a density of 199,900 cells per mL. That bloom appeared to be scum on the surface of the water, with wider streaks and bands of material visible across the surface.

The only cyanobacteria warning statewide was still in place on Province Lake in Wakefield and Effingham, a little more than an hour’s drive from Laconia. That warning was issued on Aug. 13, and remains in effect. The waters there were resampled on Aug. 27, and identified dolichospermum density too numerous to count. According to the report, the material resembled green clouds. 

A cyanobacteria warning is issued on a waterbody when samples exceed 70,000 cells per mL at multiple locations. A watch may be issued based only on a photograph, when the cyanobacteria density is approaching 70,000 cells per mL, when only one sample exceeds 70,000 cells per mL, or when the bloom material has passed. 

Cyanobacteria reports provide information from a specific point in time and may not reflect current conditions on a given body of water. NHDES staff advise the public to avoid making contact with the water in areas where bloom material is observed, as well as restricting pet access to the water.

Warnings do not close a body of water to recreation, but DES staff advise activities near visible bloom material should be avoided. Cyanobacteria material grows lake-wide, and accumulates on the shoreline due to wind, wave and boat action. The whole waterbody may not be simultaneously affected, but material can move around to various parts of the lake.

When a warning is issued, resampling is performed weekly until a bloom subsides, according to DES staff. Warnings are issued between May 15 and Oct. 15.

And there weren’t any fecal bacteria advisories on Laconia beaches as of Thursday afternoon. Bacteria advisories at Lake Opechee, Bond Beach, Bartlett Beach and Weirs Beach were lifted on Aug. 21. 

The Healthy Swimming Mapper does display fecal bacteria warnings across many of New Hampshire’s beaches, but not at all of them. NHDES staff does not sample the public beaches in Laconia, the city’s Parks & Rec Department does. 

That’s the case for numerous municipalities in the Granite State. Call your city or town hall to learn about local fecal bacteria advisories.

Temperatures are expected to remain moderate through the long weekend, with forecasted highs in Laconia reaching 78 on Monday.