On 9 August 2022, eleven researchers from seven countries left Bremerhaven, bound for the Arctic. On board the research ship Heincke, the RISING expedition – an initiative of the Helmholtz Young Investigator Group ARctic JELlies (ARJEL) at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) – had begun. The international team included experts from the AWI, GEOMAR and the University of Bergen. Their goal: to survey jellyfish along a poleward oriented line of latitude: from northern Norway, through the Barents Sea to the western coast of Svalbard – so as to gather a fundamental basis of data on jellyfish diversity and distribution.
The Arctic is changing faster than any other part of our planet. The fjords of Svalbard are especially hard-hit by melting glaciers and are increasingly influenced by the inflow of Atlantic Water. These rapid changes in environmental conditions, which have taken place over the past few decades, have also led to changes in the region’s plankton and fish communities: the team of scientists on board the Heincke conducted comparative analyses of the biodiversity in fjords, the open ocean, and their associated water masses. They also collected water and sediment samples in order to find traces of DNA (“environmental DNA”) left behind by jellyfish. Now that they’re back on dry land and at the AWI laboratories, the researchers will compare the DNA gathered with existing DNA sequences, in order to determine which jellyfish species they found traces of.
A further goal of the RISING expedition was to investigate the role of jellyfish in Arctic and Atlantic food webs. To do so, the ARJEL team will evaluate the DNA they found in the stomachs of predator species and trace them back to their prey: “These studies can tell us whether or not jellyfish are an important food source for predatory zooplankton and fish,” explains Charlotte Havermans, head of the ARJEL team. In order to learn more about what jellyfish themselves feed on, the researchers plan to create fatty-acid and stable-isotope profiles for the jellyfish and other members of the food web. The insights gained will be essential to making forecasts on the effects of possible shifts in the distribution ranges of certain jellyfish species.
“The preliminary outcomes of the expedition are very promising,” says Havermans. “The jellyfish experts on board counted nearly forty different species in the nets, which represents a significant percentage of all jellyfish fauna observed in the Arctic to date.” There were also a number of surprising findings in the course of the expedition, including some species never observed so far north. Future studies will determine whether this was due to the species’ habitats expanding with warming waters, or merely due to gaps in previous sampling efforts.