The beaches of Norderney, one of the German Wadden Islands, are littered with dead blue jellyfish. It is not really abnormal for this time of year, biologists say, but why there are so many now is still a mystery.
Jellyfish, jellyfish and more jellyfish, as far as you can see. The beaches of Norderney have been littered with them for several days now. The current has thrown the lifeless cnidarians ashore in recent days, scaring off many hikers.
“There are always jellyfish on the North Sea coast,” says biological oceanographer Berit Finkennest. “What is striking now is that there are indeed so many.”
According to the National Park House, the jellyfish that have washed up are carrot-mouth jellyfish, whose umbrella can be up to 60 centimeters in diameter. According to the Wadden Sea Conservation Station, the breeding area of this jellyfish species is in the Atlantic Ocean and the English Channel. Only with the current do the animals reach the North Sea and eventually wash up.
“It is unclear what could be the cause of this abundance of jellyfish,” says Berit Finkennest. “There are several possible causes. For example, jellyfish populations could benefit from warming seas due to climate change. There is also evidence that the cnidarians, in their sedentary phase, find additional living space as so-called polyps on the foundations of offshore wind turbines. However, concrete data on the occurrence of jellyfish over longer periods is still lacking,” says Finkennest.
Hikers have already expressed their concerns, but experts say the jellyfish are dead and completely harmless. However, it is recommended not to touch them.
At the beginning of November, our coasts were also inundated by blue jellyfish. The stormy weather took care of that. “The jellyfish that wash up dry out or are buried under the sand. Within a few days, when the spring tide comes, they disappear automatically, say marine biologists from the Flanders Marine Institute (VLIZ).