Blue-green algae has been found on the north coast of Derry and Antrim.
Scientists noted an increase in the amount of the potentially toxic algae at Lough Neagh at the beginning of August, and had established it was in the Bann River system. The Bann flows from Lough Neagh to the Atlantic, joining the sea just beyond Coleraine.
The algae had already been detected in the Bann River system and scientists were warning it could spread up the north coast - where its presence closed bathing waters in Portstewart and Portrush last year.
Heavy rain in recent weeks had increased the chances of the algae spreading — biologists had expected that the large-scale blooms in Lough Neagh would gradually spread along the Toome Canal which runs alongside the Lower Bann.
Blue-green algae, scientific name Cyanobacteria, naturally occur in inland waters, estuaries and the sea. But when their numbers become excessive they can choke bodies of water to the detriment of other aquatic organisms.
Lough Neagh has been particularly prone to heavy growths because of the amount of nutrient in the water. Much of this nutrient, a lot of it nitrates and phosphates, comes from from several sources including artificial fertilisers and slurry/manure derived from livestock that runs-off the land when it rains.
The fact that the lough bed is excavated commercially also adds to the problem that is now spreading downstream
Bathing is not recommended by the authorities at the Barmouth, between Portrush and Portstewart, the estuary of the Lower Bann River and is not an identified bathing site.
The National Trust has posted an “advice against bathing” notice.
Recognised bathing sites in the area remain open to swimmers, but authorities in the area have remained vigilant.
The BBC reports that patrols by the Department of Agriculture, Environment and Rural Affairs and local bathing water operators, including Causeway Coast and Glens Council and the National Trust, have been increased.
Pets are especially susceptible to the algae, and owners have been warned not to let dogs near the growths.
