Climate change winners

Jellyfish are increasingly invading the Arctic Ocean

A yellow hair jellyfish

(Bild: AFP)

In contrast to many other sea creatures, jellyfish are among the winners of climate change. A study by the Alfred Wegener Institute (AWI) in Bremerhaven has shown that rising water temperatures in the world's oceans could allow them to penetrate further and further into the Arctic Ocean in the future. In a computer model, researchers exposed eight Arctic jellyfish species to rising water temperatures, which are to be expected as a result of climate change.

The result: with one exception, all of the species studied could significantly expand their habitat towards the Arctic between 1950 and 2014 and between 2050 and 2099. The study was published in the journal "Limnology and Oceanography".

Yellow hair jellyfish spreading northwards
According to the results, the yellow hair jellyfish, known as the fire jellyfish, which occurs in the Baltic Sea, is spreading particularly strongly northwards. "It can almost triple its habitat," said AWI marine biologist Charlotte Havermans. Only one species studied (Sminthea arctica) recorded a decline of 15 percent, as it retreats to colder depths at high temperatures. According to the data, jellyfish also benefit from nutrient inputs and overfishing. If climate change exerts stress on marine life, cnidarians, which include jellyfish, can often prevail against food competitors such as fish, said first author Dmitrii Pantiukhin. In Svalbard, the crown jellyfish has already taken over an entire fjord, emphasized Havermans.

"Many jellyfish feed on fish larvae and eggs, thus delaying or preventing the recovery of fish populations that have come under pressure and are also usually heavily managed by humans," said Pantiukhin. Scientists are already talking about an impending global "squeezing" of the oceans. This can also be seen in the fact that over the last 15 years, people in the Mediterranean have been affected more frequently by jellyfish stings, said Havermans.

Fish population under pressure
It is still unclear how the advance of the cnidarians northwards will affect Arctic fish stocks. "There is much to suggest that important Arctic fish species such as the polar cod, whose larvae and eggs are often eaten by jellyfish, will come under even greater pressure," said Havermans.