Warnings against using or drinking water from the largest of the Killarney lakes have been issued following the appearance of a potentially toxic algal scum.
The scum has been identified at a number of locations along the shores of Lough Leane, the most popular of the lakes with tourists, boatmen and fishermen. Thousands tour it by motorised boat each summer and there are numerous hotels, guesthouses and golf courses along its shoreline.
The water has become discoloured and is blue-green or greenish-brown at the worst points.
Preliminary results of tests indicate low levels of algal toxins, according to a statement issued by Kerry County Council. High levels of phosphorus had already led the council to put up notices warning of a potentially toxic algal bloom along its shore three weeks ago and these remain in place.
Yesterday the public were advised against using the lake water for cooking or drinking and they were told not to swim or paddle where scum was present.
Fishermen should also avoid contact with waters in those areas, Mr Mick Boyce, a senior engineer, said. He stressed the risk to public health was low but added that small animals and dogs were particularly vulnerable.
An estimated 30 tonnes of phosphorus go into the lake each year and there has been no significant reduction, despite a public outcry about pollution and a range of recommendations to protect what is one of the central tourist attractions in the town's multi-million euro tourist industry.
A three-year study of the lake, following the first toxic bloom in 1997, identified as the causes of the pollution the spreading of agricultural slurry and fertiliser, detergents and fats and oils from the tourist industry, septic tanks and the council's own lack of proper sewage facilities in outlying villages. The study found that most of the septic tanks attached to one-off houses were found to be inadequate and not functioning properly.
While strict new guidelines for septic tanks have been implemented, agricultural by-laws have not yet been adopted by the county councillors, despite being drawn up for almost three years. The clean-up of the lake will cost about €17 million and will take a number of years.