Anti-Nuclear Commandos? Jellyfish Attack a French Nuclear Plant Again

For the second consecutive year, the Gravelines nuclear power plant in northern France had to scale back operations and shut down some of its reactors due to the arrival of jellyfish swarms.

Sponge-like, organized and punctual

On August 11, 2025, these sponge-like invertebrates clogged the seawater intake filters feeding its cooling system. At the time, EDF announced the installation of new monitoring cameras and a partnership with the Sustainable and Responsible Fishing association to regulate their populations.

With disturbingly punctual timing, they struck again on August 10, triggering the automatic shutdown of two reactors, while the power output of a third was halved to prevent any runaway. In a statement, EDF explained that this massive arrival of jellyfish had no impact on the safety of the facilities or the safety of the personnel.

Rather than an unlikely annual stunt aimed at highlighting the risks of nuclear power, these gatherings of cnidarians in sensitive parts of the plants are closely linked to climate change.

If the Earth has long seen jellyfish blooms in summer, these “booms” are now amplified by overfishing, eutrophication (excess nutrients in water), habitat degradation, aquaculture, and the rapid rise of ocean temperatures, which primarily translates into higher reproduction rates.

A Global Threat

Currently, the vast majority of nuclear power plants do not have the equipment necessary to cope with such volumes of jellyfish, and sadly they are not the only aquatic invertebrates capable of disrupting their operation.

In 2021, salps, gelatinous organisms resembling small worms, forced a South Korean facility to shut down two of its reactors to clear its cooling systems.

For decades, a very different bloom has been observed near a Florida nuclear plant: American alligators taking over its drainage canals.