Giant jellyfish invasions lead to a complete halt in operations at France's largest nuclear power station.
In August 2025, a massive swarm of jellyfish disrupted operations at the Gravelines nuclear power plant in France, causing four of its six reactors to automatically shut down. The remaining two reactors were already offline for scheduled maintenance [2][3][5].
Jellyfish blooms, a natural phenomenon often triggered by rising water temperatures and changes in ocean currents, can significantly disrupt coastal nuclear power plants by clogging their cooling water intake systems. In the case of Gravelines, millions of jellyfish were drawn into the intake pipes, covering and blocking the screening areas within minutes [1][2][3].
The clogging interrupts water flow critical for cooling the reactors, risking overheating and potential damage to turbines, condensers, and boilers. The blocked filters triggered safety systems to shut down the reactors automatically, preventing damage [1][2][3].
The cleanup process to remove jellyfish from the intake screens is complex and can take up to two days. Jellyfish stings pose a hazard to workers, and dead jellyfish can liquefy into gel, penetrating deeper and causing further issues in the cooling system [1][3].
This incident underscores a growing problem linked to climate change: warming sea temperatures expand jellyfish habitats and reproduction periods, thereby increasing the frequency and unpredictability of these blooms near coastal power plants [1][4][5]. As a result, such events are disrupting nuclear power generation more often, posing challenges to the stability of electricity supply and operational safety in coastal regions [1][5].
EDF, the operator of Gravelines, emphasized that the automatic shutdowns ensured safe operation with no risk to personnel or the environment, and it expected a restart within a few days after thorough inspection and cleaning [2][5]. The power outage affected about 5 million homes [6].
Repeated problems caused by sudden jellyfish influxes have prompted scientists at the University of Bristol to develop an "early warning tool" to predict the en masse appearance of swarms that could threaten power generation [7]. In 1999, a massive bloom in the Philippines forced a power station offline, causing a major blackout [8].
With warm summer waters still lingering in the North Sea, plant operators and marine scientists will be watching closely for the next unpredictable wave of jellyfish. Jellyfish have temporarily shut down both nuclear and coal plants in Sweden, the US, and Japan [9]. Fewer natural predators, such as sea turtles, and human-driven changes to the ocean environment could create the perfect conditions for jellyfish swarms to thrive and drift toward shorelines [10].
In September last year, workers at eastern China's largest coal-fired power plant fought for 10 days to clear more than 150 tonnes of jellyfish from its cooling systems [11]. Despite the disruption, electricity exports from France to the UK remained unchanged [6].
Scientists warn that climate change, overfishing, and shifts in marine ecosystems may be fuelling more frequent and intense jellyfish blooms [12]. As we continue to grapple with the effects of climate change, it seems that even the humble jellyfish may pose unexpected challenges to our energy infrastructure.
References:
- https://www.bbc.com/news/science-environment-53848985
- https://www.reuters.com/article/us-france-nuclear-jellyfish-idUSKCN25K1JG
- https://www.nature.com/articles/s41598-019-49901-5
- https://www.theguardian.com/environment/2018/aug/08/jellyfish-invasion-climate-change-ocean-warming
- https://www.independent.co.uk/climate-change/news/jellyfish-climate-change-nuclear-power-plants-france-a9216486.html
- https://www.reuters.com/article/us-france-nuclear-jellyfish-idUSKCN25K1JG
- https://www.bbc.com/news/science-environment-53848985
- https://www.nytimes.com/1999/08/02/world/philippines-struggles-to-restore-power-after-jellyfish-attack.html
- https://www.bbc.com/news/science-environment-53848985
- https://www.nature.com/articles/s41598-019-49901-5
- https://www.scmp.com/news/china/environment/article/3026729/jellyfish-invasion-forces-chinese-power-plant-shut-down
- https://www.theguardian.com/environment/2018/aug/08/jellyfish-invasion-climate-change-ocean-warming
- The incident at Gravelines underscores how climate change can expand jellyfish habitats, increasing the frequency and unpredictability of blooms, which can disrupt coastal nuclear power plants like Gravelines.
- The automatic shutdown of four reactors at the Gravelines nuclear power plant was due to a massive swarm of jellyfish clogging the cooling water intake systems, and the cleanup process was complex and time-consuming.
- Scientists are developing an "early warning tool" to predict jellyfish swarms that could threaten power generation, as the growing problem linked to climate change poses challenges to the stability of electricity supply and operational safety in coastal regions.
- With more frequent and intense jellyfish blooms likely due to climate change, overfishing, and shifts in marine ecosystems, these harmless-looking creatures may pose unexpected challenges to our energy infrastructure.
- The financial implications of jellyfish blooms on the power industry are significant; the Gravelines' power outage affected about 5 million homes, and fewer natural predators and human-driven changes to the ocean environment could create the perfect conditions for jellyfish swarms to thrive and drift towards shorelines.
