Nature
PUBLISHED
Fetch your calendars, lads. It looks as if France is getting a new annual holiday: Jellyfish Swarming Nuclear Power Plants Day.
For two years running, the Gravelines nuclear power plant in northern France has had to reduce and shut down units of operation due to the arrival of swarms of jellyfish. On August 11, 2025, the invertebrates clogged filters that take in seawater to feed the cooling system.
Now, a near-identical event has occurred as this time EDF ceased some operations as a precaution on the evening of Monday August 10, “following the massive arrival of jellyfish.” The jellyfish triggered the automatic shutdown of two units, and a further unit had to be reduced to 50 percent capacity as a precaution.
EDF has since announced that while some maintenance continues in getting the units reconnected to the national electricity grid, the situation “has no consequences for the safety of the facilities, the security of personnel or the environment.”
So, why August? Are the jellyfish staging some kind of annual protest against nuclear energy? The truth to their timekeeping lies in the increasingly testing summer Europe and much of the world is presently enduring.
Earth has long experienced jellyfish blooms, but whereas they used to be a natural event triggered by seasonal cycles, we are seeing an escalation due to human-induced events such as overfishing, eutrophication, habitat degradation, aquaculture, and rapid climate change.
Ocean warming is expected to increase the population sizes of numerous jellyfish species as higher temperatures promote reproduction rates (though this effect is likely species-specific as some thrive in cooler temperatures).
The European Union’s climate monitoring service recently announced that July saw the world’s oceans hit their hottest temperatures ever recorded, in part due to the unprecedented Super El Niño that’s having a catastrophic influence on environments globally.
To put it simply, the nuclear power stations simply aren’t ready for that volume of jelly, and that’s not all they have to worry about.
Another invertebrate known as the salp has a bit of a thing for clogging up nuclear power plants, too. In 2021, these ocean blobs took out two nuclear power reactors in South Korea.
Such events are an unfortunate and expensive delay for one of the cleanest energy sources. So, what are the nuclear power plants to do?
In response to the 2025 swarm, EDF announced it had installed surveillance cameras for enhanced monitoring. They’ve also teamed up with the non-profit France Pêche Durable et Responsible to build a network of fishers that can launch fishing operations when jellyfish numbers reach a critical mass.
And hey, it wouldn’t be the first time we’ve tried to fish our way out of a marine crisis. Just look at what people are doing with lionfish.
