In an unusual and alarming turn of events, France’s Gravelines nuclear power station—its largest such facility—was compelled to cease operations after being overwhelmed by a massive swarm of jellyfish. The sudden shutdown reflects growing environmental vulnerabilities that coastal infrastructure now faces.
Late Sunday night, four of Gravelines’ six reactors were automatically taken offline when jellyfish clogged the plant’s cooling-water filters. These reactors—numbered 2, 3, 4, and then reactor 6 a few hours later—were forced to halt as filter drums at the pumping stations became blocked by what the operator EDF described as a “massive and unpredictable” swarm. Importantly, the plant’s remaining two reactors were already offline, undergoing planned maintenance, at the time of the incident, resulting in a complete operational shutdown of the facility. EDF assured the public there was no risk to safety, staff, or the environment.
Situated between Dunkirk and Calais in northern France, Gravelines draws its cooling water via a canal connected to the North Sea. Each of its six reactors has a capacity of 900 megawatts, making it one of the country’s most significant contributors to the national electricity grid.
Experts warn that such remarkable jellyfish blooms are becoming more frequent, driven largely by rising sea temperatures. Derek Wright, a marine biology consultant with the U.S. National Oceanic and Atmospheric Administration (NOAA) Fisheries, highlighted that warmer waters extend the reproductive window for jellyfish, enabling them to breed more rapidly and in larger numbers.
The species involved in this incident was the Asian Moon jellyfish—a jellyfish native to the Pacific Northwest—first documented in the North Sea in 2020. It has also been implicated in similar disruptions to nuclear power plants in China, Japan, and India. These jellyfish thrive in calm, plankton-rich waters such as ports and canals and are known to travel globally by stowing away in the ballast water of vessels.
While these jellyfish pose no threat to human health—they lack a venomous sting—the incident underscores the unintended consequences of climate change on energy infrastructure. “Everyone talks about nuclear being clean, but we don’t think about the unintended consequences of heat pollution,” Wright remarked, pointing to how human-induced warming is creating unforeseen challenges for coastal facilities.
This incident at Gravelines serves as a stark reminder that even the most robust and high-tech installations remain vulnerable to ecological shifts. As global temperatures continue to climb, and marine species extend their ranges into new habitats, we may see more disruptions to critical infrastructure. The episode also raises broader questions about the resiliency of nuclear power systems in an era defined by accelerating climate change.
