A swarm of jellyfish has caused the closure of two reactors at a nuclear power plant in Scotland. The plant, at Torness, uses seawater as a coolant; but the jellyfish clogged filters in the intake pipes, prompting operators to shut down the reactors until the filters could be cleared.

The notion of jellyfish as nuclear reactor incapacitators isn't without precedent. For example, in 2006, jellyfish blocked the filters at a reactor in Japan, which shut down automatically. Two years later, a similar event caused the manual shutdown of the Diablo Canyon plant in California. In 1999, the temporary jellyfish-enforced closure of a coal-fired power plant in the Philippines "plunged 40 million people into darkness and sparked rumors of a coup d'etat," the NSF reported.

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Although jellyfish in the water are a natural hazard, they are a hazard that may be becoming more common. A 2008 National Science Foundation report was titled "Jellyfish Gone Wild" and concluded that environmental circumstances are tilting into jellyfish's favor. It noted, for example, that jellyfish are among the only creatures that can adapt to ultra-polluted, oxygen starved waters known as Dead Zones, which are increasing in number and area; that the over-harvesting of fish removes jellyfish predators and fish that eat the same food as jellyfish; and that increasing water temperatures may expand the species' geographic and seasonal ranges. This last point was underlined in a recent report that highlighted increasing blooms of some jellyfish in the northeast Atlantic.

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Operators of the Torness plant say there is no danger to the public and that they expect the reactors to be operational again next week. Meanwhile, they, and plant operators elsewhere, will be keeping an eye out for further jellyfish swarms and for anything else that might cause an obstruction: such as the seal that, two weeks ago, found itself trapped after chasing fish into the water intake chamber of a plant in England.

Photograph of Torness Nuclear Power Station Breakwater in foreground and Dunbar lifeboat in harbor (by Lisa Jarvis via Wikimedia Commons).