Électricité de France (EDF) shut down three [1] reactors at the Gravelines nuclear power plant late Monday after a massive jellyfish swarm clogged intake systems.
The incident highlights the vulnerability of critical energy infrastructure to biological surges and the broader impact of changing marine ecosystems on power stability.
The Gravelines plant, located in northern France on the coast of the English Channel, relies on seawater to cool its reactors. A dense swarm of jellyfish entered the cooling-water intake, which created a risk of overheating the systems. To prevent a technical failure, plant operators initiated a precautionary shutdown of three [1] reactors.
While reports on the timing of the event varied between 2025 and 2026 [2, 3], the shutdown occurred on Aug. 11. The facility is recognized as the largest nuclear plant in France.
Experts link the surge in jellyfish populations to a combination of environmental stressors. These include warming seas caused by climate change, plastic pollution, and the effects of overfishing. These factors often reduce the number of natural predators that typically keep jellyfish populations in check, allowing blooms to reach sizes capable of disrupting industrial operations.
EDF operators are managing the situation to ensure the intake systems are cleared before restarting the reactors. The plant continues to monitor the English Channel waters for further biological incursions that could threaten the remaining operational units.
“Three reactors at the Gravelines nuclear power plant were shut down as a precaution.”
This event demonstrates how climate-driven shifts in marine biology can create tangible risks for land-based energy production. As ocean temperatures rise and ecosystems destabilize, 'biological fouling'—the accumulation of organisms on wet-cooling systems—may become a more frequent operational hazard for coastal power plants globally.
