People have been told not to bathe in the largest of the Killarney lakes because of potentially toxic algae, Kerry County Council has said.
The council has identified an increase in algal growth at a number of locations around Lough Leane in Killarney.
"Members of the public are advised not to bathe or paddle in water if there are visible signs of algal growth in the vicinity which can be identified by a green, blue or brown colour in the water or along the shoreline," Kerry County Council said in a statement.
Advisory signage has been erected at a number of locations on the lake shoreline.
People have also been advised to ensure that they keep their pets under control as such algal accumulations can be harmful if ingested by small animals, particularly dogs, the council added.
The council also said that water from the lake should not be used for cooking, drinking or washing.
The situation is being monitored closely on an ongoing basis by Kerry County Council, a spokesperson added.
It is the second such warning for the lake this year.
In June, algal blooms were identified on both Lough Leane and its sister lake Muckross Lake after a prolonged sunny dry spell.
Toxic algae has been an annual feature on Lough Leane for over thirty years and a three-year study identified the cause as phosphate enrichment linked principally to agriculture, forestry and septic tanks.
A stream from the Killarney Wastewater Treatment Plant which entered Lough Leane was the source of pollution in the River Laune, the Environmental Protection Agency (EPA) said in July.
However Uisce Éireann said the Killarney Wastewater Treatment Plant was not overloaded and had capacity.
It said effluent discharge was compliant year to date.
The water authority said that while deterioration in water quality had been identified, the root cause of this was not known.
