COEUR d'ALENE - Evidence of a blue-green algae species capable of producing potentially dangerous toxins has been found in Fernan Lake water samples for the second time this year.

The Panhandle Health District and the Idaho Department of Environmental Quality issued a health advisory Friday warning residents to use caution when coming into contact with Fernan Lake water.

"It's a little late for us to see this," said Kristin Larson with the DEQ in Coeur d'Alene. "We haven't seen a bloom like this at Fernan in the fall since I came here in 2008."

The first health advisory this year was issued June 28 and remained in place until July 22.

A toxin that may be produced by the Anabaena blue-green algae species can cause a rapid progression of neurological symptoms in animals, such as muscle spasms, decreased movement, labored breathing, convulsions and death.

Symptoms have not been documented in humans, but considering the effect Anabaena has on animals, the public is advised to avoid any activity that could lead to ingesting the lake water.

Children and pets are particularly susceptible. This precaution is specially applicable to areas where water is an uncharacteristic green color and where unsightly thick green mats are present along shorelines. Drinking water from the lake may be dangerous if toxins are present; the toxins cannot be removed by boiling or filtering the water.

People are encouraged to enjoy catch and release fishing. If you choose to eat fish from this area, it is recommended that you remove all fat, skin and organs before cooking since toxins are more likely to collect in those tissues.

Blue-green algae are naturally occurring, microscopic bacteria. Many species occur in Idaho surface waters and only some species release toxins under certain conditions. Anabaena blooms occur in water conditions of optimal temperature, oxygen, and when nitrogen is unavailable and phosphorus is abundant. These circumstances are most common during the warmer months of late summer.

Often excess nutrients associated with algae blooms are caused by pollution from human activities. Water quality improvements can be expected to reduce future algae blooms, so the Idaho DEQ is working with residents and landowners to implement nutrient reduction projects.

"I think awareness is increasing," Larson said. "We just published a document we are about to send to the EPA for approval, a document that is kind of a prescription to decrease the amount of nutrients going into Fernan Lake."

The public will be advised when the concern no longer exists.