Using a small robotic sub, scientists from Columbia University have captured rare video of arctic jellyfish slithering along the bottom of the Chukchi Sea near Barrow Alaska. The footage came as a complete surprise to the researchers, who weren't expecting to see jellyfish during the Arctic winter.
Credit: Earth Institute, Columbia University
The scientists' research, published in Marine Ecology, shows that a species of large jellyfish known as Chrysaora melanaster is capable of surviving the arctic winter in its adult form, a life stage known as medusae. Prior to these observations, which were made from 2011 to 2014, scientists thought that the under sea conditions were too harsh for adult jellies during the winter months, and that this species could only survive under the arctic ice during its stage as a polyp - a formless blob that releases tiny baby medusae in the spring.
To capture the video, marine biologist Andy Juhl and his colleagues from Columbia University's Earth Institute set off on snowmobiles from Barrow Alaska to various locations along the frozen Chukchi Sea. After drilling holes through the 1.2m-plus ice, the researchers sent a small underwater vehicle into the frigid waters with a camera. To their amazement, the submersible captured haunting images of the large medusae, some of them dragging their 30cm-long tentacles behind them. The jellies use these tentacles to snatch meals off the seafloor.
The new paper suggests Chrysaora melanaster is capable of living in its adult form throughout the winter months, and possibly even live for years. Juhl now suspects that cold winters are actually really good for jellyfish in the medusae stage; the thick layer of sea ice may acting as a shield, protecting the jellies from turbulent waters. Meanwhile, cold water is lowering their metabolism, allowing the jellies to subsist on very little food. "Life under sea ice is like living in a refrigerator - everything slows down," said Juhl in a statement, adding that jellyfish blooms may follow one or two years of heavy sea-ice cover because many adults survive.
Indeed, this area of Alaska is subject to dramatic variations in jellyfish numbers each year. Some years there are hardly any, and other years there are so many that fishing nets become inundated with them. The new study could tell us something about the jellyfish population dynamics that drive these cycles. On a more troubling note, warming waters caused by climate change could be bad for the northern jellies, who are benefiting from the cold waters and ice cover (unlike other jellies, who are among the greatest beneficiaries of global warming).
But there's still one lingering question: Do these jellies sting?
"I don't know," said Juhl. "There aren't that many people around there swimming to find out."