An algal bloom which has turned parts of the Blessington lakes in Co Wicklow a luminous green has been described as dangerous to humans and pets by the environmental charity An Taisce.
The colour of the water has been compared to that of Lough Neagh this summer when beaches on the lake were closed after pet dogs and wild birds died.
Algal blooms in lakes in the Republic, while not as severe as that in Lough Neagh, have caused the temporary closure of beaches at Lough Lene in Co Westmeath and Keeldra in Co Leitrim and Lough Derg bordering counties Galway, Tipperary and Clare in recent years. The luminous green-coloured water was also seen in the Lakes of Killarney.
The change in colour is attributed to agricultural run-off, urban waste water, quarries and industry, An Taisce said.
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Concern has also been expressed that the Blessington lakes are a vital source of water for people in greater Dublin and parts of surrounding counties
Dr Elaine McGoff, head of advocacy with An Taisce, told The Irish Times that while the levels of algal bloom and pollution were not as extreme as Lough Neagh, “Lough Neagh was 10 years in the making and it happened because the warning signs were ignored. These are our warning signs.”
She said the blooms were dangerous to humans, birds and aquatic life, and could kill animals while also causing gastroenteritis in humans.
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Dr McGoff said the pollution was caused by years of algal blooms sinking in cold water and rising again when the water warmed up. “Even if we stopped putting excess nutrients into our lakes and rivers now we would still see algal blooms forming for years to come.”
She said one of the biggest sources of the pollution was most likely from farming. “We have seen farmers campaigning against the EU moves to end the derogation which allows them spread higher levels of fertiliser on land – they are arguing vociferously for their right to keep polluting. We need politicians to stand up and stop this.”
Uisce Éireann assured consumers in the Dublin region that their water was safe to drink. In a statement the authority said “the raw water supply to Ballymore Eustace water treatment plant is taken from Poulaphouca Reservoir (Blessington lakes) and is monitored continuously via 24/7 instrumentation, a laboratory sampling programme and visual inspections of the reservoir”.
“Further quality analysis and checks take place through each step of the treatment process and in the distribution network to ensure the water supplied to customers is safe to drink. Algae blooms do periodically occur for a variety of reasons, but do not typically impact the treatment process at Ballymore Eustace water treatment plant,” said Uisce Éireann.
Research undertaken by Foras Na Mars The Marine Institute has shown that patterns of harmful algal blooms have changed, showing a clear recent increase in their average monthly abundances, peaking later in the year compared to the previous decade. The data from recent years also shows a notable increase in the number of weeks these organisms are present each year.
