Recently, beachgoers and visitors to harbors along the north coast of Zealand have observed an unusual phenomenon: blue jellyfish. These jellyfish, which normally belong in the North Sea, have been carried into the Øresund with ocean currents, as reported by TV 2 Kosmopol.
Jens Peder Jeppesen, a marine biologist and aquarium manager at the Øresund Aquarium in Helsingør, states that it is rare to see blue jellyfish in this area. “I have heard that they have been seen all the way down to Copenhagen and in many places along the entire north coast, where they have been driven in,” he says. Normally, the blue jellyfish are found in the North Sea and near Iceland, but bottom currents can occasionally bring them to the Øresund.
According to John Mogensen, head lifeguard of the North Zealand lifeguard service, the blue jellyfish are often mistaken for jellyfish. However, they differ in that they can sting, albeit milder than the red jellyfish, as their venom cells release less poison, and their tentacles are shorter, reducing the risk of being stung.
In Norway, blue jellyfish are more common, but this year there are unusually many of them, as reported by the Norwegian media outlet VG. NRK noted at the end of June that the last five to six years have seen an increase in the number of blue jellyfish, and in many places, there are now more blue jellyfish than red ones, which would have been unthinkable 20 years ago. Marine researcher Tone Falkenhaug attributes this changed pattern to climate change and warmer seas.
Jellyfish consist of 95 percent water and drift with ocean currents like plankton. They cannot control their movements but can regulate their depth. These predators are older than dinosaurs and have existed for more than 500 million years. Their gelatinous consistency makes them difficult to study, meaning that scientists still know relatively little about them.