6 cyanobacteria blooms reported on Winnipesaukee

There were six reported cyanobacteria blooms on Lake Winnipesaukee in the area of Moultonborough Neck on Thursday, and another on Mirror Lake in Tuftonboro, as of Thursday afternoon.

Three of those locations, identified with black triangles on the New Hampshire Department of Environmental Services Healthy Swimming Mapper, have associated photographic reports, but no water samples have been collected. 

Those locations were reported on Aug. 28 and 29, respectively, all along various areas of Moultonborough Neck. 

Two other locations along Moultonborough Neck are identified with red triangles, meaning a sample was collected there following DES staff receipt of a photographic report and testing indicating the presence of cyanobacteria density in excess of 70,000 cells per mL, the state benchmark. 

The third location identified with a red triangle is found on Long Island, across a small channel from Moultonborough Neck. The citizen report was submitted on Aug. 13, and sampling results taken the same day indicated a cyanobacteria density in excess of 70,000 cells per mL.

The Mirror Lake cyanobacteria report was observed by a citizen on Aug. 25, and testing on a sample collected the same day indicated a cyanobacteria density of 199,900 cells per mL of several types. 

Check the Healthy Swimming Mapper at des.nh.gov/water/healthy-swimming/healthy-swimming-mapper.

The Cyanobacteria Harmful Algal Bloom Program is tasked with the monitoring of Granite State waterbodies when a member of the public reports a potential bloom. A cyanobacteria warning is issued across an entire lake when samples show cell concentrations in excess of 70,000 cells per mL in multiple locations. 

Warnings are not based on evaluation of toxins in any discrete location, but rather when excessive cell density indicates the likelihood of toxicity. They’re precautionary measures against short-term exposure to cyanobacteria and, when a warning is issued, resampling is performed weekly until the bloom subsides. Warnings are issued by NHDES staff from May 15 through Oct. 15. 

A cyanobacteria watch differs from a warning in that it encourages public vigilance in case a bloom occurs. Some watches are upgraded to warnings, and sometimes a bloom may pass before a warning is issued. Watches are active for one week upon issuance. Resampling of a location only occurs if more bloom reports are received. Watches are issued year-round.

A watch could be issued based on a photo until NHDES staff can test a water sample, if the density is approaching but has not exceeded 70,000 cells per mL, if the density reaches the state standard in only one location, or if the bloom passes before sample testing is conducted.

There were two cyanobacteria warnings statewide Thursday, on Province Lake in Effingham and Wakefield, and on Tucker Pond in Salisbury.

And there won’t be any more fecal bacteria advisories on New Hampshire beaches until next year. 

The Beach Inspection Program monitors public beaches for the presence of such bacteria from Memorial Day through Labor Day, and issues warnings if a water sample contains high levels. 

City of Laconia Parks & Rec Department staff monitor municipal beaches on the same timeline as NHDES. 

Enterococci is used as the indicator fecal bacteria on coastal beaches, and E. coli is used at freshwater beaches.