UPDATE: No-swim advisory remains at Longboat Key

UPDATE: The latest round of testing shows acceptable levels of bacteria at Lido Beach, but a no-swim advisory remains in place on Longboat Key, county health officials announced Tuesday.

Officials announced Friday an earlier no-swim advisory had been lifted for Siesta Beach.

Additional test results will be available Thursday.

Previously: Sarasota County health officials issued a no-swim advisory for Siesta Beach, Longboat Key and Lido Beach on Thursday after tests showed elevated levels of bacteria in the water.

The beaches are still open, but in a news release, officials advised against water recreation while the warning remains in place. The no-swim advisory was issued because of higher-than-acceptable levels of enterococcus bacteria.

County officials believe natural causes are responsible for the elevated bacteria levels. Response teams saw wrack lines of decaying algae and dead fish, bacteria reservoirs that are associated with an ongoing red tide bloom. The teams also saw bird tracks on the beaches, and large amounts of bird activity can increase bacteria levels. Recent rains are another factor that can wash pollutants into the water.

The elevated bacteria levels can cause illnesses, especially among the young, elderly or those with weak immune systems. The release advised against eating shellfish collected at any beach with a no-swim advisory, though healthy finfish can be eaten if filleted.

No-swim advisories were also issued for Venice Pier Beach and Brohard Beach.

Additional water quality test results will be available Friday. The no-swim advisory will be lifted when the bacteria returns to acceptable levels.