MILFORD >> Visitors at Silver Sands State Park were greeted with a sign Aug. 24 ?\u2013? this past week ?\u2014? that stated no swimming was allowed due to high bacteria levels in the water. But, that didn\u2019t stop three high school students from enjoying their day of tanning and picnicking on the beach in the afternoon. Cierra Natowski of Winsted, and Damarius Dy-Dajnowiz and Erik Grenning, both of Torrington, said they actually did not realize they weren\u2019t supposed to swim ?\u2013? on Wednesday ?\u2014? , despite the signs at the entrance to the beach from the parking lot. No lifeguards or state parks personnel were visible that afternoon and the three friends saw many people in the water throughout the day. (Lifeguard staffing at Connecticut\u2019s shoreline state beaches, including Silver Sands, was cut from seven days per week to five, covering only the periods when there usually are the largest crowds.) ?\u2013? Wednesday ?\u2014? It was the second day the state park\u2019s coastal waters were closed to swimming last week; swimming was initially prohibited Aug. 23 in the waters of four inland state park beaches. Heavy rains Aug. 21 led to ?\u2013? Tuesday ?\u2014? closures at Indian Well in Shelton, Kettletown in Southbury, Wadsworth Falls in Middlefield and Wharton Brook in North Haven as well, according to water quality reports from the state Department of Energy and Environmental Protection. Water quality issues The closures vary throughout the season and locations. In the July 17 water quality report the agency released, for instance, swimming areas at Lake Waramaug State Park in Kent and Squantz Pond State Park in New Fairfield were closed due to the presence of so-called indicator bacteria. On June 1, Chatfield Hollow State Park in Killingworth and Wharton Brook State Park in Wallingford were closed for the same reason, but reopened two days later after retesting. In some weeks, however, such as the week of June 9, all state park beaches were open for swimming with no closures listed. The July 1 water quality report noted \u201cAll Swimming Areas Open for Holiday Weekend.\u201d Silver Sands closures Chris Bellucci, a supervising environmental analyst for the DEEP, said that Silver Sands has swimming closures more than other state shoreline beaches (Hammonasset, Rocky Neck and Sherwood Island) because of its urban location. Stormwater runoff contributes to high indicator bacteria levels, so after significant rains, many urban state park beaches may be closed, Bellucci said. Water samples from four coastal and 19 inland beaches are collected weekly between Memorial Day and Labor Day and analyzed by the state Department of Public Health, Bellucci said, though additional analyses will be done during the week if there are heavy rains. What analysts look for is high levels of indicator bacteria such as enterococci in salt water and E.coli in fresh water. When the indicator bacteria levels are high, that lets analysts know that there is a heightened risk of pathogens in the water at levels in which swimmers could get sick, said Scott Szalkiewicz, a health program supervisor for the state Health Department. The indicator bacteria itself is not dangerous, but higher levels signal other potential dangers. \u201cThe bacteria itself is an indicator that something could be in there,\u201d Szalkiewicz said. \u201cThe indicator bacteria tell us when it might not be a good idea to swim there.\u201d He said rather than do much deeper analyses of water samples looking for all of the potential pathogens that could be present that would lead to gastrointestinal or upper respiratory infections, scientists rely on the indicator bacteria to judge whether the water is safe for swimming. TESTS, VISUAL SURVEY When state workers go out to take water samples, they also do a visual survey of the water, Szalkiewicz said, and beaches will be closed if algae blooms are observed. State park waters may also be closed to swimming immediately following a storm if more than an inch of rain fell in a 24-hour period, Szalkiewicz said. The visual analyses and keeping track of rainfall help officials to act quickly to close beaches while state labs test water samples. Lab results usually take one day to be returned, he said. Pathogens that could cause gastrointestinal or upper respiratory infections get into the water from storm runoff because of sewage overflows and rain water picking up animal feces, Szalkiewicz said. PUBLIC FEEDS BIRDS One way to prevent high levels of bacteria in state waters, Bellucci said, is not attracting water birds such as ducks and geese to the parks. Many visitors will feed the birds, which keeps the birds coming back. \u201cInland, we have more problems with waterfowl,\u201d he said. \u201cThey poop a lot and that\u2019s a lot of where the bacteria comes from.\u201d Bellucci said the department is also paying attention to cyanobacteria count as cyanobacteria actually does produce toxins in the water. So far, there are no reports of anyone getting sick as a result of cyanobacteria in state-managed waters, Bellucci said. Municipal beaches such as West Haven\u2019s, which have been closed bywater quality problems this summer, are regulated by local health departments. Anna Bisaro can be reached at 203-680-9915.