Blue-green algae has returned to Lough Neagh with the first confirmed cases of 2025, the Northern Ireland Environment Agency (NIEA) has confirmed.
Noxious blooms of the algae covered large parts of the lough, the UK’s largest freshwater lake by surface area, during the previous two summers and also affected other waterways and beaches in the region.
The NIEA said two reports had been made from locations on Lough Neagh and were verified on April 10 and 11 at Traad Point and Kinturk (Curran’s Quay).
This followed earlier algae reports at Martray Lough, Ballygawley and Ballysaggart Lough in Dungannon.
Environment Minister Andrew Muir previously said he expected the algae to return this year.
A Department of Agriculture, Environment and Rural Affairs (DAERA) spokesman said: “Minister Muir is on record a number of times saying that there are no quick fixes, with problems decades in the making and decades in the fixing.
“It is therefore unfortunately no surprise that we are beginning to see algae blooms reappear again this year, particularly with the good weather.
“The severity and scale of the problem we will be facing this summer will be dependent on a number of factors.
“Work is well under way to tackle the problem through the Lough Neagh Action Plan and the minister is determined to turn the tide on water quality, but we know that this will be a long-term endeavour.”
Lough Neagh supplies 40% of Northern Ireland’s drinking water and sustains a major eel-fishing industry.
Nitrogen and phosphorus from agricultural fertiliser running off fields and from wastewater treatment is a contributory factor in the blue-green algae blooms.
The spread of the invasive zebra mussel species is also understood to have played a role in the blooms, as they have made the water clearer, allowing more sunlight to penetrate, stimulating more algal photosynthesis.
Climate change is another factor as water temperatures rise.
The Stormont Executive last year launched an action plan to deal with the environmental crisis at the lough.
Mr Muir told his Stormont scrutiny committee last week that spring should be about renewal, “not news reports of blue-green algae”.
He added: “Significant work is already under way to tackle the nutrient overload in our rivers, lakes and loughs.
“I will continue to lead and seek support for the tough decisions needed over the time ahead to improve our waterways and tackle climate change.”
The DAERA spokesman added: “NIEA encourages members of the public to report a suspected bloom through the Bloomin’ Algae App or e-mail emergency-pollution@daera-ni.gov.uk with a photo, if possible, and details on the location of the potential bloom.
“All reports of blue-green algae can be viewed on the DAERA blue-green web viewer Blue-Green Algae – Confirmed Locations.
“NIEA will continue to record events and review any significant increase in bloom numbers.”
