‘Blue-green algae’ do-not-swim warning at Benone in North Derry lifted after successive green results
A warning not to swim at Benone in North Derry due to the presence of ‘blue-green algae’ has been lifted.
The Department of Agriculture, Environment and Rural Affairs (DAERA) Bathing Water Team’s sampling teams had been monitoring beaches close to the mouth of the River Bann after potential harmful cyanobacteria was identified at Benone on August 21.
Last Friday laboratory results for samples taken at the North Derry beauty spot prompted a red alert under the Inter-Agency Blue Green Algae Protocol.
Causeway Coast and Glens Borough Council then issued a temporary ‘do not swim’ advisory while the the RNLI Beach Lifeguard Service operating at Benone red-flagged the popular bathing, surfing and water sports spot.
DAERA said that once a red alert has been issued two ‘green results’ must be achieved before the beach can reopen for bathing.
Two further samples were lifted at Benone (on August 23 and August 26) returning green results.
“Council was advised of the second green result at 4.30pm on August 27. The RNLI Beach Lifeguard Service was subsequently informed and signage removed from site.
“Throughout this process Council has followed the Inter-Agency Blue-Green Algae Monitoring Protocol,” CC&GBC advised on Thursday.
DAERA said: “Temporary advice against bathing at Benone Beach has been removed (August 27) after monitoring indicated that blue-green algae was no longer a risk.
“The bathing water operator, CC&GBC, has been informed and temporary advice against bathing signage has now been removed. The public is advised to check the NI Bathing Water Quality Dashboard and on-site signage for the latest updates.
“The temporary advice against bathing had been issued for Benone on Friday (August 22, 2025) after blue-green algae had been identified during routine water quality monitoring by DAERA.”
‘Blue-green algal blooms’ are not caused by algae but by bacteria called cyanobacteria, which create potentially harmful toxins known as microcystins.
High levels of nutrients (phosphorus and nitrogen) in Lough Neagh have resulted in blooms flowing out into the Atlantic via the Lower Bann sporadically affecting bathing water quality from Portstewart to Magilligan.
Beaches have been red-flagged over the past three summers as a result of cyanobacteria.