Jellyfish populations are surging because of rising sea temperatures and overfishing, which leaves them with few predators and no competition for plankton, reports the New York Times. Fishermen are finding nets “filled with more jellyfish than fish,” said one, and swimmers are reporting increasing numbers of jellyfish stings, which can take weeks or even months to heal. In Barcelona recently, some 300 people were treated for stings within a few hours.
“But the big problem is not on the beach—it's what’s happening in the seas,” said a jellyfish expert, one of many who believe the population surge is cause for profound alarm. “These jellyfish are a message the sea is sending us saying, ‘Look how badly you are treating me.'"