Consult swimming mapper before heading out into the water this weekend

There are numerous reports of cyanobacteria blooms across Lake Winnipesaukee heading into the weekend, according to staff at the New Hampshire Department of Environmental Services.

A reported bloom along the shoreline of Moultonborough Neck, which was initially reported on July 22, was tested and results showed cyanobacteria density exceeded 70,000 cells per mL. A sample collected the same day indicated a density of cyanobacteria too numerous to count. 

Another bloom reported in the Tufotonboro area of the lake, near Cow Island, similarly was tested, and results indicated a cyanobacteria density exceeding 70,000 cells per mL, the state benchmark. That bloom was reported on Aug. 11, by an individual boating on the lake. 

The report described the bloom as mixed, with both surface scum and material dispersed throughout the deeper waters. 

A sample collected the same day the report was made indicated a cyanobacteria density of 153,450, including both gleotrichia and dolichospermum, two types of cyanobacteria. 

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

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

There were three reports in and around The Broads in Gilford, which resulted in samples being taken, but the cyanobacteria density did not exceed 70,000 cells per mL. Crescent Lake and Lake Wentworth similarly had numerous sample results where the cyanobacteria density hadn’t exceeded 70,000 cells per mL, as of Thursday afternoon. 

Nearly every area of the lake had numerous reports with photographs, though those potential blooms hadn’t yet been sampled. The areas of Lake Winnipesaukee from Gilford Town Beach, past Governor’s Island and up through Meredith were the only ones without any reported cyanobacteria blooms.

The only active cyanobacteria warning statewide was issued on Aug. 13, for Province Lake in the areas of Effingham and Wakefield. Cyanobacteria warnings are not based on toxin evaluation, but occur at densities when toxin production may be likely, according to NHDES staff. They’re precautionary measures for short-term exposure to cyanotoxins. 

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

A watch may be issued for a waterbody “to serve as a statement to be on the watch for a potential cyanobacteria bloom.” Some watches become warnings, and sometimes the bloom will pass before a warning is issued. Watches are active for one week. 

Resampling only occurs if more blooms are reported and watches are issued year-round as needed.

And at the beaches in the City of Laconia, fecal bacteria sampling was conducted on Aug. 13. Results were not yet available on Thursday afternoon. Call the city’s parks and recreation department at 603-524-5046 for specific information regarding public beaches. 

NHDES staff do not sample Laconia beaches for fecal bacteria, but they do sample many others statewide. The NHDES map didn’t indicate any Lakes Region beaches with fecal bacteria advisories, but it’s best to contact officials in your town hall to get the most accurate information regarding local bacteria advisories.