Which types of jellyfish are there in the Arctic Ocean today – and which will still be there tomorrow?

No matter whether it’s the Baltic, North Sea, Atlantic or Pacific: these days you can see jellyfish virtually every time you take a stroll along the beach. Over the past few decades, the number of these eye-catching cnidarians has grown so rapidly that, in some regions, the fish population has suffered – and in some cases, the gelatinous raiders are even claimed to be dominant. Yet so little is known about the lifecycle, distribution and diversity of jellyfish (cnidarians) and similar marine organisms like comb jellies and tunicates. For example, we know virtually nothing about which species of these (in some cases only very distantly related) phyla there are in the Arctic Ocean, how frequently they can be found there, or what their roles are in the polar food web.

“We know so little because you can’t simply catch jellyfish in a net. Their soft, fragile bodies are often destroyed when hauled out of the water, or are too quickly digested in the stomachs of predators, which means that new, complex methods are called for, in order to confirm their existence and understand their role in the ecosystem,” explains Dr Charlotte Havermans, a biologist at the University of Bremen and the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).

The young researcher detailed precisely which methods will be required in the course of her proposal for a new Young Investigators Group, which was approved. With the financial backing of the Helmholtz Association and the AWI, next year Charlotte Havermans will create a four- to five-member research group, which will use the latest technologies to create a jellyfish inventory for the Arctic Ocean. “In the course of several ship-based expeditions, we’ll deploy a range of camera systems in the water column and beneath the sea ice, investigate the stomach contents of various marine organisms, search for the genetic fingerprints of jellyfish and co. in the water, and analyse sonar data, which will hopefully give us new insights into the occurrence and distribution of cnidarians and comb jellies,” Havermans adds.    

Drawing on these and many other types of data, the new group leader hopes to subsequently determine how many different species of gelatinous organisms there are in the Arctic Ocean, where they hail from, what they feed on, and whether or not they are dependent on sea ice at a certain point in their lifecycle. Further research questions include whether or not the total number of jellyfish is actually on the rise; whether the territories of individual species will shift as a result of climate change; whether they are prey for Arctic fish species and/or migrating species from the North Atlantic, or conversely are decimating these fish species’ offspring; and whether Arctic jellyfish species are capable of adapting to climate change. “When I began gathering all these questions for the proposal, I got so excited about the topic that I couldn’t imagine working on anything else,” enthuses the researcher, who grew up in Belgium.

For Havermans, the promise of support from the Helmholtz Association was like a dream come true. As she recalls, “I read the email over and over again, just to be 100% sure I wasn’t dreaming. The Helmholtz Association and the AWI have given me the opportunity to continue working in Bremerhaven for the years to come, and to exclusively focus on this exciting topic. I can’t wait to get started!”