A "massive influx" of jellyfish forced Electricite de France SA to shut three units at its Gravelines nuclear power plant this week and reduce output at a fourth, [1]reports Bloomberg . Just as summer temperatures surged, 3.2 gigawatts went offline — and the power utility was already facing cuts other nuclear sites as high temperatures reduced the river water available for cooling.

More [2]details from ScienceAlert :

> As [3]Politico reports , the Gravelines nuclear power plant spent hundreds of thousands of euros in 2025 to stop this happening again, only to see a repeat 12 months later... Increasing temperatures in the water [4]can produce more of the plankton and animals that jellyfish feed on, as well as accelerating life cycles and extending breeding seasons....

>

> It's not just jellyfish that have a habit of disrupting human energy infrastructure. Last year in Connecticut, a single raccoon caused more than a thousand power outages, as reported by [5]CT Insider . It's not clear exactly what the raccoon did, but we do know it somehow got into a substation and caused damage to the equipment in there. The unwitting act of sabotage left more than 2,500 customers in the area without power at one stage — though repairs were swiftly carried out.

Reuters reported Tuesday on [6]how the French utility responded to their jellyfish swarm :

> EDF has installed fixed cameras at the intake canals and on the filter drum screens to detect any incoming blockages as soon as possible, an engineer told Reuters... The company has also partnered with a French fishing organisation and a sea rescue organisation, which monitor for swarms and can raise an alert to launch targeted trawling operations by fishermen to reduce the swarm's density before it reaches the plant, the engineer said. The fishing boats were deployed [last] Saturday after an initial alarm was raised, limiting the impact from the swarm. The jellyfish that are already on site are being removed with vacuum trucks, he said. No new jellyfish are arriving, so cleanup is finishing, which should lead to a quick restart of the units, they added...

>

> Scientists warn such events could become more common due to factors including global warming, the arrival of invasive species, habitat loss of predators and over-fishing.

Thanks to Slashdot reader [7]Bruce66423 for sharing the news.



[1] https://fortune.com/2026/08/11/jellyfish-swarms-knock-out-3-2-gigawatts-of-french-nuclear-power/

[2] https://www.sciencealert.com/swarming-jellyfish-just-shut-down-a-nuclear-reactor-for-the-second-time

[3] https://www.politico.eu/article/swarming-jellyfish-overrun-french-nuclear-plant-on-same-date-two-years-in-a-row/

[4] https://pml.ac.uk/news/hundreds-of-jellyfish-wash-ashore-southwest-beaches-what-is-causing-such-large-blooms/

[5] https://www.ctinsider.com/news/article/ct-power-outages-monday-eversource-ui-20237607.php

[6] https://www.reuters.com/business/energy/jellyfish-hit-french-nuclear-plant-shuts-down-three-reactors-2026-08-11/

[7] https://www.slashdot.org/~Bruce66423