Bacteria levels remain high on Whittemore Lake, affecting Bennington town beach

Bennington’s town beach on Whittemore Lake.

Bennington’s town beach on Whittemore Lake. STAFF PHOTO BY JESSECA TIMMONS

A cyanobacterial warning at Bennington’s Whittemore Lake Monday. 

A cyanobacterial warning at Bennington’s Whittemore Lake Monday.  STAFF PHOTO BY JESSECA TIMMONS

By JESSECA TIMMONS

Monadnock Ledger-Transcript

Published: 11-21-2023 3:01 PM

Modified: 11-22-2023 2:40 PM


State officials announced Nov. 16 that the cyanobacteria levels at Whittemore Lake, which includes Bennington’s town beach, still exceed safe levels.  

According to a report posted by Michaele Condon, beach inspection program coordinator for the Watershed Management Bureau in the Water Division at the New Hampshire Department of Environmental Services (NHDES), the highest levels of density of the toxic bacteria were found near the dam, exceeding 91,800 cells/mL, far past the state limit of 70,000 cell/mL. Other samples collected from around the lake ranged from 28,500-32,000 cells/mL.

The New Hampshire Division of Water Resources requires that the Town of Bennington post a swimming advisory at the beach until cyanobacteria levels recede. The water will be tested again on  Nov. 30. According to Kate Hastings at NHDES, the  bacteria blooms are “potentially toxic,” and advises people to wear gloves and a mask and wash their hands thoroughly with clean water if they come in contact with the water in the lake. 

According to Condon, climate change is a factor in increased incidence of toxic cyanobacteria blooms in New England’s ponds and lakes. 

“Climate change is leading to more extreme weather events, with more wet and drought years, and cyanobacteria blooms are common in both. Heavy storms bringing extra storm water runoff, or drought conditions, bringing warmer waters, often contribute to cyanobacteria blooms,” Condon stated. “This was a record-breaking year for the New Hampshire Department of Environmental Services CyanoHAB Program, which has the responsibility is to monitor cyanobacteria blooms throughout NH and inform the public of potential health risks. The NHDES CyanoHAB Program issued 69 cyanobacteria advisories at 47 different water bodies this year.”

Cynaobacteria is naturally occurring organism which can cause harmful algae blooms in freshwater bodies of water. According to the state DES, cyanobacteria are a potential public health danger because they may produce toxins, collectively referred to as “cyanotoxins,” that can be consumed by organisms in the food chain and released into the water when cells die.

The amount and type of toxin produced varies over time and from lake to lake. A cyanobacterial bloom may produce very little to no toxin in one lake, but a later bloom in the same lake could produce a large toxin concentration. Cynaobacteria appears as a green scum-like layer which tends to build up on the downstream side of a lake or pond. 

Condon said it is not easy to identify the source of a bloom, but that causes often include phosphorus and nitrogen runoff from septic systems, lawn and garden fertilizer and stormwater. 

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“The bloom will eventually subside over time,” Condon said.