The UK’s most extensive lake is confronting an ecological catastrophe, but the efforts to save it are failing | Contamination

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The UK’s largest lake, Lough Neagh, is expected to experience its most severe year of potentially toxic algal blooms to date, as efforts to address the issue remain stalemated.

As the ban on eel-fishing in the lake continues to be extended, with local fishers experiencing a 60% decrease in income since 2023, there have been 139 incidents of cyanobacteria (blue-green algae) blooms recorded in the lough and its surrounding water channels, according to government pollution tracker. This is more than three times the amount recorded at the same time in 2024 (45). This information covers the 400 sq km freshwater lough, its tributaries, and smaller associated water bodies, including Portmore Lough and Lough Gullion.

At the central part of this extensive 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 in 2024’s records. As of August 25, there had been 35 confirmed cases, in contrast to 42 during the same period in 2024, according to the Department of Agriculture, the Environment and Rural Affairs (DAERA).

Lough Neagh’s repetitive algal blooms, which suffocate aquatic life, result from an excess of phosphorous and nitrogen entering the lough system. Sixty two percent of this pollution comes from farming sources — including farm run-off, fertilizers, and animal waste, while 24% is attributed to aging wastewater treatment plants, and 12% from seepage from septic tanks. The residual 3-4% is suspected to originate from various industrial and household sources around the lough.

The data from Northern Ireland’s devolved government highlights local claims that this year’s blooms have been the “worst ever” in people’s lifetimes.