Dozens of beaches across Massachusetts remained closed for swimming Monday due to dangerous levels of bacteria and/or algae.

Swimming bans were in effect at a total of 41 beaches as of Monday morning. 

Swimmers from Cape Cod to Western Massachusetts were impacted. State officials recently released an interactive dashboard for this information, which includes a map showing where water quality has been deemed dangerous. 

North of Boston, a stretch of bacteria-filled water shut down swimming at Ocean Avenue in Salem, Nahant Beach, and Lynn Beach. In the city, Malibu Beach, Tenean Beach, and Savin Hill Beach all remained closed for swimming. 

This summer, heavy rains have caused water quality issues at a large number of beaches, but fewer were closed to swimming Monday than on Friday. 

The state tests more than 1,000 beaches regularly, often closing them due to “bacterial exceedance,” which refers to the levels of Enterococci or E. coli in the water. Officials measure these types of bacteria to get a read on how many pathogens are in the water, which can make people very sick. 

Some beaches are also closed due to harmful algae blooms, which release toxins into the water. 

Five beaches were closed to swimming due to both bacteria and algae Monday: Waushakum Beach in Framingham, Houghton’s Pond in Milton, Carbuncle Pond Beach in Oxford, and Kingsley Beach and Lamberts Beach in Westfield. 

The state’s interactive dashboard can also be used to view the results of water testing at all Massachusetts beaches. Swimming bans are normally in place for a few days. 

The beaches are still open to the public for recreational activities that don’t involve going into the water. 

A number of New Hampshire beaches were also closed for swimming due to fecal bacteria advisories to start the week.