Research by the AWI research team shows that jellyfish play an important, previously unknown role in the diet of amphipods. The Arctic is changing rapidly due to climate change. It is affected not only by rising surface temperatures, but also by warm currents from the Atlantic Ocean, which are increasingly flowing into the Arctic, changing the structure and function of ecosystems and also causing species from warmer areas (such as jellyfish) to come to the Arctic.
Now, using DNA metabolic coding techniques, researchers at the Alfred Wegener Institute have shown for the first time that these jellyfish serve as food for amphipods in Svalbard during the polar night and therefore play a greater role in the Arctic food web than previously thought. They recently published an article describing their findings in the scientific journal Frontiers in Marine Science.
Arctic continentalization and its impact on marine life
In recent years, warm, salty water from the Atlantic Ocean has increasingly entered the European Arctic. The Norwegian archipelago of Svalbard has also been affected by this "Atlanticization": Kongsfjorden on the west coast has been converted into an Atlantic water system; the water temperature during the polar night (November to February) rises by about 2 degrees Celsius every decade. These changes also lead to biological migration, as species from warmer waters also flow into the Arctic with warm Atlantic waters.
Charlotte Havermans, head of the ARJEL junior research group at the Alfred Wegener Institute and the Helmholtz Center for Polar and Marine Research (AWI), said: "Some jellyfish species are particularly prone to poleward spread. Entering the Arctic. In 2022, when we were in Kongsfjorden during the polar night, we were very surprised to see that the fjord was filled with jellyfish life, consisting of many different species and life stages, which seemed to be the most dominant zooplankton in winter. "
In the past, jellyfish were considered a nutritional dead spot in marine food webs, but recent research has shown that jellyfish are important prey for marine invertebrates and fish.
"We therefore wanted to know whether the jellyfish in Konsfjord were also food for other organisms, especially during the dark season of the polar night, when other food sources are limited," said Havermans.
To answer this question, Annkathrin Dischereit, a doctoral student in the research team, analyzed the stomach contents of various amphipods. Over the course of a month, they used baited traps and hand nets to regularly collect samples of four different amphipods (Ocean cockroach, Seto cockroach, Ctenophora squamata and Pinless squid) during the polar night.
AWI researchers used DNA cellular coding to determine the food lineage of small crustaceans. This cutting-edge method detects short genetic fragments in the stomach and then compares them to a database of genetic references to determine the prey species to which the fragments belong. "We found a large number of jellyfish in the stomachs of the amphipods, from the largest jellyfish in the fjords to tiny polyps," explains Charlotte-Hafermans.
Using DNA metabolic coding technology, the AWI team was able to identify and classify the soft-bodied parts of jellyfish and other organisms, even after they have been nearly digested. "We have shown for the first time that amphipod scavengers feed on the remains of jellyfish. This has only been demonstrated before in experimental settings."
All species studied feed on plant and animal matter. In addition to jellyfish, crustaceans and macroalgae are important food components for some species, while fish such as polar cod are an important food component for others. It remains to be clarified whether amphipods feed on fish eggs, larvae, carrion, or fish excrement. In addition, it remains to be determined whether jellyfish are a winter survival food or a permanent prey for these creatures throughout the year. Researchers have long believed that jellyfish have low nutritional value, but this has only been investigated in a few species.
New understanding of Arctic marine ecosystems
This study provides new insights into Arctic food webs during the polar night and is the first natural, non-experimental evidence that jellyfish play a role in these food webs.
Charlotte Havermans concludes: "The thriving and diverse winter jellyfish communities in Konsfjord are clearly used as a food source. So far, we know nothing about the role of jellyfish as prey in this area. We also don't know, for example, that the species Gammaridea feeds on jellyfish, not in the Arctic and not elsewhere."
The question now is whether this only applies to polar nights when food supplies are limited. The ARJEL junior research group at the Avi Institute hopes to continue investigating this issue. Because "jellyfish may be one of the winners from climate change, they will continue to spread during global warming. The researchers also predict that as temperatures continue to rise, jellyfish will become more common in the Arctic. Therefore, their role in the food web may become increasingly important. However, so far, our understanding of this is limited, especially in the polar regions."
"With this study, we reveal a hitherto unknown key link in the Arctic food web. This is crucial because we need to understand how jellyfish integrate into food webs and spread across the rapidly changing Arctic. This also applies to adjacent continental shelf seas, where ten percent of the world's fisheries take place."
Compiled source: ScitechDaily