An alert for a toxic blue-green algae bloom on Black Lake has been posted.

The county Public Health Department wants people to be aware that the state Department of Environmental Conservation (DEC) has received a report from SUNY ESF that there is an algae bloom present on Black Lake.

The bloom was initially reported in the bay south east of Tavern Island (the Narrows) on July 21, and it increased in intensity over the next week.

Surface algae was also observed along the south and east shorelines of Conger Island.

An open water sample collected further north in the lake on the same date had elevated toxin levels.

Most algae are harmless and are an important part of the food web. Certain types can become abundant and form blooms under the right conditions. Some algae can produce toxins that can be harmful to people and animals. These are collectively called harmful algal blooms (HABs).

Algae blooms most frequently occur in nutrient-rich waters, particularly during hot, calm weather. Blue-green algae are naturally present in lakes and streams in low numbers.

Blue-green algae can form HABs that discolor the water or produce floating rafts or scums on the surface of the water. These can cause health risks to people and animals when they’re exposed to them. Because it’s hard to tell a harmful algae bloom from other algae blooms, the DEC recommends avoiding contact with any floating rafts, scums, and discolored water.

Blue-green algae blooms can reduce the recreational value of a water body due to unpleasant appearances and odors and can cause a variety of ecological problems, such as reduced oxygen levels.

Harmful blue-green algae blooms can cause health effects when people and animals come in contact with them. Symptoms can include nausea, vomiting, diarrhea, skin or throat irritation, allergic reactions or breathing difficulties. Blue-green algae can also produce toxins that affect the liver and nervous systems when water is consumed in sufficient quantities.

The Health Department has these recommedations:

• People, pets and livestock should avoid contact with water that is discolored or has scums on the surface. Colors can include shades of green, blue-green, yellow, brown or red. If contact does occur, wash with soap and water or rinse thoroughly with clean water to remove algae. If pets get into the algal bloom they should not be allowed to lick/clean their fur. Instead wash them well with clean water.

• No swimming, water skiing, jet skiing or tubing in areas with algal blooms.

• Do not eat fish caught in the bloom areas as they may contain the toxin in harmful levels.

• Never drink untreated surface water, whether or not algae blooms are present. Untreated surface water may contain other bacteria, parasites or viruses, as well as algal toxins, that all could cause illness if consumed. In-home treatments such as boiling or disinfecting water with chlorine or ultraviolet (UV) or water filtration units DO NOT protect people from blue-green algal toxins.

• If washing dishes in untreated surface water is unavoidable, rinsing with bottled water may reduce possible residues.

• Stop using the water and seek medical attention if needed if symptoms such as vomiting, nausea, diarrhea, skin, eye or throat irritation, allergic reactions or breathing difficulties occur while in contact with untreated surface waters. However, swimming, bathing or showering with water not visibly affected by a blue-green algae bloom is not expected to cause health effects.

For more information go to http://www.dec.ny.gov/chemical/83310.html