Lough Derg is out of bounds to bathers because of the presence of a potentially toxic substance. Cian McCormack reports.
North Tipperary County Council has posted warning signs on the lake's shoreline bathing areas, advising people not to swim in the lake following the discovery of potentially toxic algal blooms.
According to the council, the algal bloom's toxicity has to date tested negative but it has the potential to develop into blue green algal bloom - a toxic plant growth blamed for the death of two dogs at Castelough on Lough Derg during the 1990s.
Toxins given off by blooms of blue green algae can cause skin rashes. The growths are sparked by warm weather and by exaggerated levels of phosphates and nitrates entering the lake from agricultural, industrial and domestic sources.
Mr Frank O'Halloran, acting director of environment, planning and corporate service with the county council, said the algal bloom was identified on July 16th during an inspection of the lake's waters.
"Various samples were taken and sent for analysis at a laboratory in Cork. We got the initial results back and they identified that generally samples were not toxic but have a risk of toxicity developing," said Mr O'Halloran.
"The results have shown that the algae can develop toxic qualities. There is some risk of a toxic element, blue green algae."
He confirmed that bathing areas on the Tipperary side of Lough Derg are out of bounds to swimmers at Luska, Terryglass, Youghal Quay and Dromineer.
"We are advising that while there is a risk, the safest thing for people to do is for them not to bathe," said Mr O'Halloran.
People are being advised to keep their livestock and animals away from the lake.
Mr O'Halloran said farmers should ensure their livestock were not drinking water from the lake and that pets should not be allowed on the foreshore of the lake to minimise contact with the algae.
The council has also advised Clare County Council about the situation, although the Tipperary side of Lough Derg is usually most affected by the bloom. The council is continuing to test the water and Mr O'Halloran said the council would monitor the situation and keep the warning signs in place until the algae abated.
Following the council's decision to ban bathing in the lake, the environmental group SOLD - Save Our Lough Derg - has called for action to prevent the causes of pollution on the lake.
Mr Paddy Mackey, a spokesman for the group, said: "The signs telling people not to bathe are an annual event and are an indictment of our attitude to water quality. Lough Derg is the jewel in the crown of our local tourist industry and we can ill afford the bad publicity caused by this ban.
"We have seen these algal blooms on the lake for some years now and they will continue to cause problems until there is a real concerted community effort aimed at cleaning up Lough Derg," he added.
"SOLD believes it is vital for all sections of the community to play their part in protecting this great natural resource. The main cause of the algal blooms is an excess of nutrients including phosphates entering the Shannon and its tributaries."
He said there was no overnight solution but the following steps had been recommended.
Mr Mackey said farmers should use fertilisers correctly and only spread slurry in suitable weather conditions; industries and businesses should prevent discharges from their premises and should train their staff to protect water quality.
Householders, he added, should use phosphate-free detergents and ensure that septic tanks were working properly.