Paris, August 11, 2025 — In a scene that sounds more like a science fiction plot than reality, France’s largest nuclear power station, the Gravelines plant, has been forced into a complete shutdown — not due to technical failure or security breach, but because of jellyfish.

Late Sunday night, four of the plant’s six reactors went offline after swarms of jellyfish clogged the water filters that feed its cooling systems, the plant’s operator EDF confirmed on Monday. The remaining two reactors were already offline for scheduled maintenance, meaning the entire facility is temporarily out of action.

Situated on France’s northern coast between Dunkirk and Calais, the Gravelines nuclear plant is a critical part of the country’s energy grid. Each of its six reactors produces 900 megawatts, drawing cooling water from a canal connected to the North Sea. EDF reported that reactors 2, 3, and 4 automatically shut down just before midnight after the filter drums became jammed by what they described as a “massive and unpredictable influx” of jellyfish. Reactor 6 followed suit several hours later.

EDF assured that there was no danger to plant safety, staff, or the environment. “This is an operational interruption, not a safety emergency,” a company spokesperson said.

Warming Seas and Jellyfish Blooms
Marine biologists link the incident to rising sea temperatures — a consequence of global warming — which have been driving increasingly frequent jellyfish blooms. Derek Wright, a marine biology consultant with the US National Oceanic and Atmospheric Administration Fisheries, explained: “Jellyfish breed faster in warmer water. In the North Sea, the period when conditions are favorable for reproduction is getting longer every year.”

Among the culprits is the Asian Moon jellyfish, a species native to the Pacific Northwest that has been spotted in the North Sea since 2020. Known for its ability to thrive in still, plankton-rich waters such as ports and canals, this jellyfish is a master hitchhiker, spreading via ballast water in large ships. It has been linked to similar shutdowns of nuclear facilities in China, Japan, and India.

While these jellyfish pose no risk to humans — they lack a painful sting — they do present a growing threat to coastal infrastructure. Their sudden swarms can overwhelm intake systems at power plants, desalination facilities, and even fishing operations.

An Unseen Consequence of Heat
Experts warn that such events may become more common as oceans warm and marine ecosystems shift. Wright added: “Everyone talks about nuclear energy being clean, but few consider the unintended consequences of thermal pollution and climate change on coastal operations.”

For now, EDF teams are working to clear the filters and resume operations, though no timeline has been given for when the reactors will be back online. Until then, France’s largest nuclear facility remains at the mercy of one of the ocean’s simplest — yet surprisingly disruptive — creatures.