WEST NEWBURY — Town health officials urge the public to stay out of Mill Pond for the time being due to the possibility of cyanobacteria in the water, which could be toxic to people and animals.

Health Agent Paul Sevigny and the Board of Health have issued a public warning. People, dogs, horses and other living creatures are urged to refrain from ingesting or coming in contact with the water until further notice, the town announced in a press release Thursday.

Ryan Goodwin, chairman of the Mill Pond Committee, noted that he has been working with the town to update water quality testing standards in the Mill Pond management plan in response to inquiries about a growth of green, scum-like algae in the causeway area of the pond. 

Testing conducted earlier this month showed normal levels of nitrogen, dissolved oxygen, chlorides and conductivity in the water, according to the town. No blooms of invasive plants were visible on the pond at the time of the water testing. The town received photographs and anecdotal information from visitors that raised suspicions the pond might contain blue-green algae.

While the town works to have additional water quality testing done, the public is advised to avoid exposure to the water — since there is no way to tell if the bloom is toxic without testing. 

Sevigny said Thursday the town was getting cost estimates for the latest round of testing.  

“Toxins can persist in the water after a bloom, so people should watch for signs of recent blooms, such as green scum on the shoreline and, 'When in doubt, stay out,'” Goodwin said, adding that people exposed to the algae bloom should immediately wash off with fresh water.

Cyanobacteria are microscopic and live in all types of waterbodies — and some can be toxic to animals and people, according to the state Department of Environmental Protection.

“Ingesting small amounts of cyanobacteria or cyanotoxin can cause gastrointestinal symptoms while larger amounts may cause liver or neurological damage," according to information from the DEP. "Contact with cyanobacteria can cause skin or eye irritation. Inhaling water spray containing cyanobacteria can cause asthma-like symptoms. Small children and pets are more susceptible to the effects of cyanotoxins than adults.” 

Since 2008, the state Department of Public Health has recommended keeping the public away from water when a visible scum or mat is present and the total cyanobacteria cell count exceeds 70,000 cells per milliliter of water, or the microcystin level equals or exceeds 14 parts per billion.

The U.S. Environmental Protection Agency notes that in addition to people and animals, toxic blooms can affect aquatic ecosystems, the economy, drinking water supplies, property values and recreational activities, including swimming, and commercial and recreational fishing.

Ideal management practices target nutrients, specifically nitrogen and phosphorus, with the goal of “reducing loadings from both point and non-point sources, including water treatment discharges, agricultural runoff, and stormwater runoff, the EPA said.

Devices that result in the mixing of lakes — for example, by air bubbling — enhance vertical mixing of the phytoplankton, which minimizes the formation of surface blooms of buoyant cyanobacteria. Also, increasing the water flow through lakes or estuaries reduces "water residence time" and inhibits cyanobacteria blooms.

Any questions or concerns can be directed to Sevigny at psevigny@wnewbury.org.

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