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Dog owners asked to avoid lakes and ponds where harmful blue-green algae blooms could be present

Algae in the Charles River swirled around a boat docked at the MIT Sailing Pavilion. Jessica Rinaldi/Globe Staff/Globe Staff

Officials from MSPCA-Angell warned pet owners this week to not let their dogs bound into lakes and ponds if they see a greenish film floating on the surface, a telltale sign that harmful toxins could be present in the water.

In a pair of tweets Tuesday, the Jamaica Plain-based organization shared tips and an advisory from the state Department of Public Health website about the potential impacts cyanobacteria algal blooms — more commonly called blue-green algae blooms — can have on animals who come into contact with it.

“Cyanobacteria cases popping up around the state,” one tweet read. “Please do not allow dogs to wade into ponds with green film on the surface — which indicates significant bacterial accumulation.”


In a follow-up tweet, MSPCA-Angell said that cyanobacteria can be deadly to pets, “so avoiding infection is critical.”

“Our Angell vets say that typically a dog has to drink infected water to get sick, but bacteria CAN enter through open wounds — so avoid all bodies of water in which blue/green algae surface film is present,” the organization said.

According to state officials, cyanobacteria can form harmful blooms in lakes, ponds, and rivers, causing it to look like a murky “pea soup,” or green paint. Although the blooms are typically blue or green, they can also look brown or red.

“These blooms may produce toxins and could make people and pets sick,” a warning from the state’s website, shared by MSPCA-Angell, says. “Call your vet immediately if your pet has been around an algae bloom and shows symptoms such as vomiting, staggering, drooling, and convulsions.”

Cyanobacteria blooms typically form in warm, slow-moving waters rich in nutrients from sources like stormwater runoff, according to the Centers for Disease Control and Prevention. They are most common in late summer and early fall, the federal agency says.


There are currently cyanobacterial bloom advisories in place at Billington Sea, in Plymouth; Crystal Lake, in Newton; Devol Pond, in Westport; Long Pond Marstons Mills and Shubael Pond, in Barnstable; and West Reservoir in Harwich, according to a list on the state’s website that was last updated Wednesday .

In July, the Charles River Watershed Association issued a public health advisory and urged people not to make contact with the water after the organization confirmed cyanobacteria was found growing in parts of the river.

The potentially harmful effects of blue-green algae has received renewed attention this summer after several stories of dog owners whose pets died after apparently being exposed to the toxins went viral online.

As of Tuesday, the state Department of Public Health said it had not received any reports of dog deaths due to contact with blue-green algae. Officials from MSPCA-Angell also said they hadn’t received any cases.

Still, when contacted by the Globe, DPH officials reiterated the potentially deadly impacts of the blooms on pets.

“Dogs can get very ill and even die from licking algae off of their fur,” a spokeswoman for the department said in an e-mail. “Rinse dogs off immediately if they come into contact with an algae bloom.”

Because it’s difficult to know for sure if a bloom is actually toxic, without first being tested, officials recommended that “when in doubt, stay out.”


For more information about blue-green algae, you can visit the state’s website.

Steve Annear can be reached at Follow him on Twitter @steveannear.