More than 50 Massachusetts beaches are closed to swimming due to bacteria or algae

Shubael Pond in Marston Mills was closed to swimmers in 2020 in response to an algae bloom and cyanobacteria.John Tlumacki/Globe Staff

See a state listing of beaches that are closed in Massachusetts: Beach closing tracker.

More than 50 beaches in Massachusetts have been closed to swimming due to bacterial and other issues, state officials said Monday.

The state Department of Public Health updated its list of beach postings online Monday, showing that the water quality was unsafe at 53 beaches, ranging from the coastline and the Cape to freshwater beaches further inland.

The number of posted beaches has dropped since the list was previously updated Friday.

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.