Health warnings prohibiting swimming in Lough Ennell have been lifted this week by Westmeath County Council.
“It is now safe for bathers, dog owners, and other animal owners to enter the water at Lilliput and all bathing areas around Lough Ennell,” said Sean O’Laoide, the county’s veterinary officer.
The results of continuous testing at various points around the lake show that the algal bloom, which caused a scum of toxic blue-green algae to accumulate on the shore presenting a potential risk to humans and animals, has now gone.
This cyanobacteria, known as microsystis, relases toxins harmful to the liver and nervous systems when its cellular structure begins to degrade.
It is particularly harmful to dogs who are much more likely to ingest such water, as the sight of algae tends to keep humans out of water.
A similar outbreak at Portlick on Lough Ree 10 years ago killed five dogs belonging to a visiting vet.
“The arrival of this algal bloom could be described as a perfect storm, where all the conditions needed for it to thrive were there. The water is nutrient rich, there was little or no movement, and there was all that sunlight for the photosynthesis,” Mr O’Laoide explained.
“Obviously, the cleaner the water, the less the chance of this happening. And though the lake’s history isn’t great, it is improving,” he continued, referring to the three-year-old, €70m sewage treatment centre in Clonmore which ended centuries of using the lake as a cesspool for the town of Mullingar.
He explained that the county council tests all the lakes in the county for this phenomenon, but that none of the others is so affected because “the water quality [in the other lakes] is better, they wouldn’t have near the same level of nutrients”.
Mr O’Laoide also offered an optimistic forecast on the issue.
“It should be that this will be the end of the problem if we achieve the objectives of the EU’s Water Framework Directive, which is required to be in place by 2021,” he continued.
“We may never see it again.,” he said.
“Something like this highlights the value of good water quality, using fish as bio-indicators like a canary in a coalmine,” he concluded.