SOUTH PORTLAND — The Maine Department of Environmental Protection has confirmed that an algae bloom in two ponds in Hinckley Park is a cyanobacteria that is toxic to animals and humans.

Toxic algae in Hinckley Park ponds

Toxic algae in Hinckley Park ponds. Photo courtesy of South Portland Parks and Recreation Department

Like last year, bluish green blobs of oscillatoria can be seen floating in both Hinckley Pond and Old Ice Pond. The two ponds are linked by Kimball Brook, which flows through the 40-acre park off Highland Avenue.

The city’s Parks and Recreation Department posted warning signs around the ponds and closed them to public use in early July, after a staff member noticed the algae had returned.

“The ponds will remain closed until later this fall when the water cools and the bloom dies off,” department officials announced. “The park is still open to the public, however, we are asking that you and your pets do not go near the water.”

The algae bloom is likely fortified by dog feces left behind in the park, as well as fertilizer runoff from yards in the neighborhood, said Fred Dillon, the city’s stormwater program manager. Both contain phosphorus and other nutrients that promote algae growth.

Dillon said the problem is made worse because people and dogs have trampled vegetation around the ponds that normally would filter and prevent stormwater runoff into the ponds. The exposed dirt adds more phosphorus to the nutrient mix.

“If people can get better control of their dogs, we may be able to reduce the problem, but it’s very difficult to address once it’s established,” Dillon said.

The DEP is conducting water tests to determine the level of phosphorus in the ponds, as well as nitrogen, which may show that dog urine is another contributing factor, Dillon said.

To help improve the environment around the pond, the city is mounting a public information campaign that will include signs along walking paths highlighting park features and explaining how and why they should be protected.

Dillon said he also will seek a DEP grant to reestablish vegetation around the ponds, which then would have to be protected from damage by people and dogs. And the city is developing a fertilizer control ordinance that would help reduce nutrient runoff into the ponds.

Toxins produced by the algae are harmful if ingested, inhaled or absorbed through the skin or eyes, according to the U.S. Centers for Disease Control and Prevention.

Symptoms are similar for humans and animals and depend on exposure. If ingested, it can cause nausea, vomiting and diarrhea within three to five hours and last for a day or two. Other effects include sore throat, nasal and ear infections, headache, joint and muscle pain, bronchitis, pneumonia, dermatitis, blisters and conjunctivitis.

If illness arises following a suspected exposure to harmful algae, the CDC recommends treating the symptoms until they subside, and seeing a doctor if they persist.

Cyanobacteria occur worldwide in calm, nutrient-rich waters, but some species produce toxins that can negatively affect animals and humans, according to the federal Environmental Protection Agency.

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