MAHOPAC, N.Y, - Blue-green algae blooms have resulted in the closing of as many as 14 public beaches in Putnam County in recent weeks and have impacted some private beaches along Lake Mahopac as well.

Health officials said they wouldn’t name the specific public beaches that had been closed because the situation is volatile and can change daily. They recommend calling the beach and checking its status before heading there.

“This is insanity; it’s never been like this,” said one Putnam County Health Department (PCHD) official.

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Last week, the PCHD had prohibited access to the beach at the Lake Mahopac Golf and Beach Club due to the algae blooms, but as of press time the club had been given clearance to reopen the beach.

Health Department officials said harmful algal blooms (HABs) are more than a simple nuisance. They can present a serious health hazard and residents should be cautious when swimming, boating or even just cooling off in waters with any algae.

“These harmful blooms are a significant issue for our county,” said County Executive MaryEllen Odell. “We have a number of beautiful lakes that have been affected. This can cause problems for recreation, and potentially for the quality of our drinking water. State funding and expertise will help us combat this problem.”

Ed Barnett, chairman of the Lake Mahopac Park District Advisory Board, said the board has been aware of the issue.

“We are working cooperatively with the county Health Department to address the beach closings,” Barnett said.

Dr. Michael Nesheiwat, interim commissioner of health, said that rising temperatures are partly to blame for the algae blooms.

“The type in Putnam is technically known as cyanobacteria,” he said. “These toxin-producing microscopic organisms are harmful to humans and animals if swallowed. At high levels, ingestion may cause nausea, diarrhea and vomiting, along with irritation of the skin, eyes, nose, throat, and respiratory tract.”

Toxic bacteria are naturally present in low numbers in lakes and streams, Nesheiwat said. However, in warm, shallow, undisturbed surface water that gets a lot of sunlight, the bacteria can grow quickly, creating a bloom. When this happens, floating scums on the water surface may appear, along with discolored water covering all or portions of a lake.

The Department of Health monitors permitted bathing beaches and performs periodic checks at regular weekly or biweekly intervals, depending on the situation. When there is a visible presence of blue-green algae, operators of permitted beaches must close their beach. Colors can also range from green, blue, brown, yellow, grey, or even red. Health officials say that contact should be avoided with any discolored water, with or without a floating covering or unpleasant odor. When the water clears, either naturally or by treatment, follow-up water testing must be conducted. Toxins can still be present even after the bloom looks like it has passed.

“Only after a satisfactory result on a water test are town and beach personnel permitted to re-open the beach,” said associate public health sanitarian Shawn Rogan. “We work closely with the towns to reopen the beach as soon as possible. If the water tests are acceptable, we can usually open a beach within two days.”

The Department of Health has four recommendations for residents to protect themselves from HABs. Avoiding exposure to all visible algae blooms is the No. 1 precaution. In addition to not swimming, even playing by the water, wading, or water-skiing may cause accidental swallowing, skin exposure or inhalation of airborne droplets, and all should be avoided. Use added caution with open cuts or sores. The second precaution is not to allow young children or pets to play in water where an algal bloom is present. The third is to wash hands and body thoroughly if any exposure occurs, and the fourth is not to use any water from lakes with algae blooms for drinking unless treated through a municipal water treatment plant.

Health officials said that there are water treatments to reduce the blooms in lakes, but prevention is by far the best tactic. Treatments can involve the use of algaecides, but they have the same precautions as any pesticide. Treatment methods, if any, are strictly a town decision, and application of an algaecide requires approval by the DEC. Other prevention efforts involve community-wide efforts to reduce plant fertilizer use, promote efficient septic system operations, and to manage stormwater. Each of these strategies for residents helps to control the level of nutrients the algae receive and may limit their growth. These tactics are supported by the DEC, but much is still unknown about the causes of HABs.

“Reducing the use of fertilizer in a community may reduce the number and severity of blooms,” Rogan said. “However, blooms have occurred in remote Adirondack lakes as well.”

Barnett said that the Lake Mahopac Park District along with the Health Department will hold a public informational meeting on Monday, Aug. 6, at the Mahopac Public Library to bring the public up to speed on the situation.

“The closing of a single beach does not mean the entire lake is at risk,” Barnett said. “It is our intention that any public notices be more specific concerning the extent of the issue. Also, and it’s really simple, common sense would indicate that if you don’t like the look of the water, don’t go in.”