Largest UK Lake - Loch Neagh In Northern Ireland - On Track For Worst Year Ever For Toxic Algae Blooms
The UK’s largest lake, Lough Neagh, is on course to record its worst year of potentially toxic algal blooms to date, as rescue plans remain deadlocked. As a ban on eel-fishing in the lake is extended yet again, with local fishers’ incomes falling by 60% since 2023, there have so far this year been 139 detections of cyanobacteria (blue-green algae) growths recorded at the lough and its surrounding watercourses, according to a government pollution tracker. This is more than treble the number for the same point in 2024 (45). The data covers the 400 sq km freshwater lough, its tributaries, and smaller peripheral bodies of water, including Portmore Lough and Lough Gullion.
At the central water body within this vast lough, rivers and wetlands system that drains nearly half of all land in Northern Ireland, along with parts of two counties in the Irish republic, the number of detections was slightly lower than 2024’s tally. As of 25 August, there had been 35 confirmed reports, compared with 42 during the same period in 2024, according to the devolved Department of Agriculture, the Environment and Rural Affairs (DAERA).
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Dr Les Gornall, a slurry expert who worked at Lough Neagh’s last major laboratory, told the Guardian 2025’s algal blooms had been “much worse than last year’s – significantly worse”, both in terms of the extent of the blooms’ coverage and the “intensity of smell” they produced. These details are not measured by Stormont’s detections, Gornall added. Researchers are still trying to pinpoint the impact of this photosynthesising bacteria on the lough’s complex ecology. But Gornall highlights that the pollution’s secondary effects, including proliferating aquatic weeds, which feed on the excess nutrients, are now visible.
Stormont has not released official statistics on phosphorus loads entering the lough system over the past 12 months, but Gornall believes a further 16,000 tonnes have gone into Lough Neagh since last year, with about 10,000 tonnes having been retained in the water column. Despite numerous promises of action from politicians, Northern Ireland’s devolved government has struggled to make progress on tackling the reasons behind the lough’s pollution amid pushback from some farming groups – with the sector contributing more than 60% of overall phosphorus pressures – and the continued underfunding of the public wastewater system. Human sewage, from the public network and domestic septic tanks, is responsible for about 36% of phosphorus inputs.
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https://www.theguardian.com/environment/2025/aug/30/uk-largest-lake-lough-neagh-faces-environmental-crisis-as-rescue-plans-stall