Marine biologists, meanwhile, say they would not be surprised if more jellyfish shutdowns occur in the future.

“It’s true that there seems to be more and more of these extreme cases of blooming jellyfish,” said Lene Moller, a researcher at the Swedish Institute for the Marine Environment. “But it’s very difficult to say if there are more jellyfish, because there is no historical data.”

The species that caused the Oskarshamn shutdown is known as the common moon jellyfish.

“It’s one of the species that can bloom in extreme areas that . . . are overfished or have bad conditions,” said Moller. “The moon jelly likes these types of waters. They don’t care if there are algae blooms, they don’t care if the oxygen concentration is low. The fish leave . . . and (the moon jelly) can really take over the ecosystem.”