Cyanobacteria watch remains in effect for Webster Lake in Franklin

There weren’t any new cyanobacteria reports submitted to the New Hampshire Department of Environmental Services across the entirety of Lake Winnipesaukee headed into the weekend, but a cyanobacteria watch remained in effect on Webster Lake.

Webster, located in Franklin and named after 19th-century statesman Daniel Webster, has two public beaches and, apparently, a fair quantity of cyanobacteria.

The cyanobacteria watch, issued by NHDES staff on Sept. 4, remained in effect Thursday afternoon. According to the description on the NHDES Healthy Swimming Mapper, which is updated in real time and provides the public information regarding relative water quality, the bloom on Webster appeared visually like green ribbons of material.

The initial cyanobacteria identified was dolichospermum at a density of 632,000 cells per mL, well-above the state benchmark. 

According to the NHDES Healthy Swimming Mapper, there were seven separate reports of cyanobacteria around Webster, three of which had been sampled and tested by NHDES staff.

Five locations where blooms were reported by helpful citizens fall on the southerly side of Webster, while another is along the northeastern shore, and a seventh is squarely in the center of the 606-acre waterbody renowned for its beauty and opportunities for outdoor recreation. 

It’s classified as a warm water fishery, species including rainbow trout, brown trout, bass, pickerel, pout and perch have been observed on the lake.

Check the Healthy Swimming Mapper, which is regularly updated and describes water quality conditions throughout the state, by navigating to des.nh.gov/water/healthy-swimming/healthy-swimming-mapper.

A cyanobacteria watch is issued by NHDES staff based only on a photo, when the cyanobacteria density is approaching, but not exceeding, 70,000 cells per mL, the state benchmark; when only one sample exceeds 70,000 cells per mL; or when bloom material has passed.

Watches differ from warnings, which are issued when sample results exceed the benchmark at multiple locations. 

The only cyanobacteria warnings statewide remained in effect on Province Lake in Wakefield and Effingham, and on Tucker Pond in Salisbury.

A cyanobacteria warning is not based on toxin evaluation, but occurs at cyanobacteria density levels when toxin production may be likely, according to NHDES staff. They’re intended to be precautionary measures for short-term exposure to toxins. When a warning is issued, resampling occurs weekly until the bloom subsides. Warnings are issued from May 15 to Oct. 15. Watches are issued year-round, if needed. 

On Lake Winnipesaukee, there were no watches or warnings in effect on Thursday, and there weren’t any new cyanobacteria bloom reports, according to the Healthy Swimming Mapper. 

NHDES staff also monitor public beaches throughout the Granite State, both coastal and inland beaches, for the presence of fecal bacteria. 

The Beach Inspection Program monitors such beaches from Memorial Day through Labor Day, so no new information will be available for the remainder of the year. 

But NHDES staff don't monitor all public beaches — for example, the public beaches in Laconia are monitored by city staff, who do so along the same timeline as NHDES. They won’t complete any more monitoring until Memorial Day next year.

Other municipalities may have their own policies regarding fecal bacteria monitoring on their public beaches. It’s best to call your town or city hall in order to receive accurate, up-to-date information to that effect.