More than 50 Massachusetts beaches are closed to swimming due to bacteria or algae – The Boston Globe

In Boston, those beaches included Malibu Beach, Savin Hill Beach, and Tenean Beach — all closed to swimming after testing found excessive levels of bacteria in the water.

When the water quality is considered to be unsafe, “the beach is required to be ‘posted’ with a sign that indicates swimming is unsafe and may cause illness,” the website said.

More than 1,100 beaches in Massachusetts are tested anywhere between daily and monthly, with most being tested once a week, according to the Department of Public Health.

Freshwater beaches are tested for Enterococci and E. coli, while marine beaches are only tested for Enterococci, according to the state. Waters are considered unsafe when levels exceed normal two days in a row. Beaches that have a history of exceeding levels multiple days in a row get posted by the state after one test shows higher levels, according to the website.

Six marine beaches in Beverly, three each in Winthrop and Salem, and two beaches each in Dennis, Lynn, Quincy, and Wareham were all posted for “bacterial exceedance.”

Two freshwater beaches in Framingham and two in Templeton, as well as Lake Quinsigamond’s Regatta Point in Worcester, were among more than 20 freshwater beaches closed to swimming for the same reason, according to the website.

Swimming at beaches with high bacterial levels can lead to symptoms including gastrointestinal issues, such as vomiting and diarrhea, respiratory, or even flu-like symptoms, according to the Department of Public Health.

One of the causes for high bacteria levels includes rain runoff, the website said.

Four freshwater beaches across the state, including three in Mashpee, were posted due to an “algae/cyanobacteria advisory,” the website showed.

Breanne Kovatch can be reached at breanne.kovatch@globe.com. Follow her on Twitter at @breannekovatch.