A large influx of jellyfish has forced the partial shutdown of the Gravelines nuclear power station in northern France after they blocked parts of its seawater filtration system. The disruption matters because Gravelines is one of France’s largest nuclear plants, and its cooling system depends on water drawn from a canal connected to the North Sea.

EDF said units three, four and six were shut, with unit three having only returned to the grid on 18 August after an earlier jellyfish-related interruption. Units one and two were operating at reduced power as a precaution; each of the plant’s six reactors can generate 900 megawatts. Jellyfish are more active in warmer months, when hot weather can increase surface plankton levels, and similar but rare incidents have affected plants in Scotland and Sweden.