A scum layer of potentially toxic blue-green algae, also known as cyanobacteria, spotted on Mashpee-Wakeby Pond on September 24 has led to a health advisory warning against swimming or making contact with the water.
The advisory is in place only for the Wakeby section of the pond, said Ashley Fisher, Mashpee’s director of natural resources. The Sandwich health department has also posted advisories at the pond, which is shared between the two towns.
“The Sandwich Department of Natural Resources has monitored [the] ponds and determined that the community should not utilize the pond for recreation or allow access to pets,” said a notice dated September 29 on the Sandwich website. The Sandwich advisory has been posted at the entrance to the Ryder Conservation Area.
The toxins that cyanobacteria can create can cause liver damage and have been known to kill dogs and pets.
Mashpee Health Agent Glen E. Harrington said that to his knowledge the health advisory is the first time that an advisory warning of cyanobacteria has been posted at Mashpee-Wakeby Pond.
A visible scum layer of the blue-green algae is one of several criteria which can trigger an advisory. Another criteria that can trigger the advisory is a cell count about 70,000 cells per milliliter.
A cell count conducted by the Mashpee’s department of natural resources last week found 40,000 cells per milliliter in the Wakeby section of Mashpee-Wakeby.
The advisory went up “out of an abundance of caution” due to the visible scum layer, Mr. Harrington said.
Mashpee-Wakeby is the second pond in Mashpee to have an advisory posted warning of cyanobacteria this summer. A cyanobacteria advisory has remained in place at Santuit Pond after going up in late July.
Cyanobacteria are a recurring problem on Santuit Pond where advisories have been posted in each of the last four consecutive summers. The potentially toxic algae are a growing problem for freshwater ponds on Cape Cod where the algae growth is fueled by nutrient pollution and a warming climate.