Loudon residents warned of blue-green algae bloom 

  • A cyanobacteria bloom in Franklin's Webster Lake in 2005. Courtesy of NHDES

Monitor staff
Published: 8/31/2016 12:11:28 AM

Loudon residents are being warned to avoid Hothole Pond due to a blue-green algae bloom.

The Department of Environmental Services issued an alert Tuesday regarding the “green hue . . . clearly visible across the entire lake.” The algae, known as cyanobacteria, can produce toxins that cause mild to severe health problems in both humans and pets.

DES said that Hothole Pond has a cell concentration of about 72,000 cyanobactria cells per milliliter of lake water, which is above the state’s threshold of 70,000.

The warning is a precautionary measure to prevent short-term exposure to cyanobacteria toxins in the Loudon water body. DES is asking people and their pets to avoid contact with the water, and for people to monitor the shoreline for changing conditions.

DES said that while cyanobacteria is naturally present in water bodies, excess amounts of the nutrient phosphorus, combined with sunlight and warmer temperatures, can cause blooms and surface scums to form.

The toxins contained in some cyanobacteria are released when the cells die. Contact with the toxins can cause skin irritation, nausea, vomiting and diarrhea. In severe cases, liver and central nervous system damage can occur.

Cyanobacteria blooms have received increased attention in New Hampshire following their first reports in the 1960s and ’70s, and especially after several dogs ingested toxins from a bloom in Vermont’s Lake Champlain and later died.

DES monitors public beaches and waters routinely. After a warning is issued, DES returns to the water body once a week until the blue-green algae bloom is no longer visible.

The warning for Hothole Pond in Loudon will remain in effect until more water samples show diminished levels of cyanobacteria.

DES is asking anyone who notices something resembling cyanobacteria to refrain from wading, swimming, drinking or allowing pets in the water, and to call 419-9229 to report the bloom.

DES is also encouraging residents to prevent future blooms by reducing their use of fertilizers and monitoring their septic systems to lower nutrients going into water bodies.

(Elodie Reed can be reached at 369-3306, ereed@cmonitor.com or on Twitter @elodie_reed.)




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