There's something in the water at Lake Ronkonkoma.

The Suffolk County Department of Health Services has closed the Town of Islip swimming beach there for more than 24 days this summer because of high levels of bacteria in the water. The department reopened the beach Thursday afternoon, saying water samples now meet state standards.

On a recent visit, the 300-foot-long stretch of sand at the Ronkonkoma Beach was empty, save for two lifeguards sitting under a canopy. Signs reading "beach officially closed" dotted the perimeter next to red flags planted in the sand.

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The only swimmers were a pair of Canada geese -- the very source of the E. coli that has shuttered the beach to bathers.

The state monitors the presence of E. coli up to a certain density in swimmable waters. At Lake Ronkonkoma, "the results kept going up and up and up above New York State standards" this summer, said Nancy Pierson, a senior public health sanitarian with the county Division of Environmental Quality. The bacteria levels at some points have exceeded the state maximum levels.

The feces of the ever-present Canada geese are the primary source of the E. coli, and both town and county officials say there's little that can be done to control the bird population because of federal and state regulations.

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"Canada geese are considered a migratory bird species and are protected under the Migratory Bird Treaty Act," state Department of Environmental Conservation spokesman Bill Fonda said in an email.

He said that any culling of the live goose population would require a federal permit from the U.S. Fish and Wildlife Service.

"We can't stop the birds from coming," said Islip parks Commissioner Kerry Bassett. "We comply whenever the health department has an issue, but we can't stop the birds, and the birds keep coming."

Prolonged exposure to E. coli bacteria can result in gastrointestinal problems, rashes and pink eye, particularly for small children and the elderly, Pierson said. No health problems have been reported to the county during the days when swimming was allowed in Lake Ronkonkoma this summer, she added.

The Ronkonkoma beach has had the most closures this summer of the 190 beaches that the county health department monitors, Pierson said. The closure was in effect from June 23 through July 2, July 5 through July 10, and again on July 12 through Thursday morning.

In 2014 the beach was closed for four days on two separate occasions because of elevated levels of E. coli and the more dangerous blue-green algae, or cyanobacteria, which can affect a person's nervous system. In 2013 the beach was closed for 17 days, including 10 days for E. coli and seven days for cyanobacteria.

Suffolk County maintains a beach hotline at 631-852-5822 and an online map at that lists current beach closures.