Council says algae are causing brown sludge and foul smells in Dublin Bay

FOUL SMELLS and the appearance of brown sludge on beaches around Dublin Bay are the result of sunny weather and not sewage, Dublin local authorities have said.

Residents in Dublin have in recent days reported sewage-like odours in the north and south bay areas, and stretching inland as far as Dundrum in south Dublin.

Diggers have also been seen removing piles of foul-smelling, heavy brown sludge from Dollymount Strand on the north side of the bay.

However, while the sludge has an appearance and smell similar to that of raw sewage, a spokesman for Dublin City Council said it was a naturally occurring algae which had overproduced because of the recent warm weather.

"It's called ectocarpus. It's a naturally occurring algal bloom caused by high amounts of sunshine."

He said the sludge, while unpleasant, was perfectly harmless, and did not contain any treated or untreated sewage. It was not in any way related to emissions from the Ringsend waste-water treatment plant. Diggers were being used to remove the sludge from beaches, as swimmers found it off-putting.

Coastwatch Ireland said while the sun did result in algae overproduction, the ectocarpus algae was particularly prevalent in Dublin Bay because of the high "nutrient content" of the water, which kept the algae fed.

Water can have a high nutrient content because of the presence of nitrate run-off from fields, industrial pollution, emissions from boats, car fumes in high-traffic areas or sewage effluent.

"The nutrient content of Dublin Bay is particularly high. The ectocarpus bloom which results in a brown goo is not sewage in itself, but the presence of sewage in water is one of the things which can increase its nutrient content," said Coastwatch spokeswoman Karin Dubsky.

However, she said there could be a different cause of the particularly strong smell in south Dublin. This could be related to the possible pollution of Booterstown creek. In recent days the creek had taken on a black appearance and was emitting a noxious smell.

A spokeswoman for Dún Laoghaire-Rathdown County Council said it was not aware of any problem with the creek, and its water division had confirmed that the odour was due to the ectocarpus algae.