Killarney’s largest lake contaminated with toxic ‘algae’

Pet owners warned to keep animals away from water with blue-green bloom

Kerry County Council is to erect warning signs after toxic blue-green 'algae' appeared over the past number of days in Killarney's largest lake, and major tourist attraction, Lough Lein.

And the Irish Society for the Prevention of Cruelty to Animals (ISPCA) has advised pet owners to be vigilant and keep their animals away from lakes or ponds that contain the bloom.

The Trout Anglers Federation of Ireland had reported the outbreak on its social media site with pictures of the pea green-like soup at a number of locations on the major angling and tourist pleasure lake, considered the jewel in the crown of Kerry tourism.

The council which monitors the lake, along with the Environmental Protection Agency, ( EPA) said the signs are being erected as a precaution. Blue-green 'algae' is not actually an algae but is made from Cyanobacteria which feed on nutrients in water.


A major outbreak of the toxic bloom in 2016 on the lake shore led to the death of a number of dogs.

The EPA has said there has been an increased number of queries in recent weeks relating to such blooms in lakes in counties Galway and Mayo and in the River Liffey at Ballymore Eustace and it warns that dog deaths are likely to increase.

Investigations are being undertaken by the local authorities involved and relevant signage is in place, the EPA said in a statement.

One of the reports to the agency “ relates to a series of dog deaths in the vicinity of Lough Mask” .

Toxicity-related dog deaths

EPA staff from the office of evidence and assessment have assisted with the provision of responses, or given guidance on the identification of Cyanobacteria to local authority staff where possible, with some material also being identified in the EPA Castlebar inspectorate, to rule out potential toxicity issues in Lough Corrib.

The reported prevalence of toxicity-related dog deaths has increased in recent years, with a significant event in Lough Leane, Co Kerry in 2016. There is likely to be significant under-reporting, while the incidence of this phenomena is anticipated to increase, the statement said.

Dr Shane O'Boyle, Senior Scientist, EPA office of evidence and assessment said blooms are part of the natural cycle in lakes. However natural blooms are intermittent. When they persist, it indicates there is an external nutrient such as phosphates which is feeding them.

Outbreaks of blue-green 'algae' occur now on an annual basis in Killarney. An in-depth study twenty years ago identified euthrophication or enrichment by phosphates as responsible for the growth.

Septic tanks and farming, as well as forestry, were identified as the prime culprits and a major programme saw a reduction in phosphates from these sources, as well as upgrading of septic tanks and slurry pits.

Killarney town’s sewage treatment plant, alongside the lakes, has come in for increasing scrutiny with questions over its capacity and efficiency being raised increasingly at council meetings in Killarney.

Sewage treatment plant

While the quality of water from the Flesk River, one of the main rivers feeding into the lower lake from the Cork border has improved, the Folly Stream, outflowing from the sewage treatment plant directly into the Ross Bay on the lake, is below standard.

Last year, monitoring undertaken by Kerry County Council and the EPA determined The Folly Stream to be “mildly eutrophic or mildly enriched”.

The council has insisted the Killarney Wastewater Treatment Plant is “fully compliant” with the Urban Wastewater Directive and the Emission Limit Values.

An assessment of the suitability of the existing wastewater treatment plant outfall point to the Folly Stream will be carried out by 2021, it has also said.

An estimated 1.1 million tourists a year now visit Killarney and the town sells around 1.56 million bed nights, according to a tourism study earlier this year commissioned by the town’s Chamber of Commerce and Tourism.

In a statement, the ISPCA advised pet owners to be vigilant and keep their animals away from lakes or ponds where they suspect blue-green ‘algae’ may bloom.

“If your pet shows signs of poisoning, such as vomiting, diarrhoea, seizures, breathing trouble or disorientation, contact your vet immediately,” the statement said.

“The ISPCA is not aware of specific bodies of water in Ireland that may be contaminated, but the heat and dry weather may have allowed more blue-green algae to bloom this year,” it said. “We advise owners who are worried about blue-green algae concentration in nearby lakes and ponds to contact their local county council which may be able to provide advice on which water bodies may be contaminated.”