In summer 2023, Lough Neagh made headlines as an unprecedented algal bloom saw the lake’s surface coated in green sludge. As the algae begin to resurface in 2024, Tommy Greene investigates the miscellany of threats that have driven the lake to its current critical condition.
Toxic ‘blue-green algae’ are gradually returning to Lough Neagh, the largest freshwater body in Britain and Ireland. A blanket of photosynthesising cyanobacteria almost completely covered the vast lough (Irish for lake or inlet) – with a surface area (nearly 400km2) greater than that of Malta – last summer and autumn.