Trophic ecology of Arctic gelatinous zooplankton

The overarching goal of this dissertation is to reject the hypothesis of gelatinous zooplankton (GZP) as a trophic dead end for the Arctic and sub-Arctic seas. To do so, I investigated the role of GZP in the diet of different invertebrate and fish species, during different seasons and at different locations. To do so, I used DNA metabarcoding of the stomach contents of bentho-pelagic amphipods and demersal and bathypelagic fish species. I also, aimed to prove the usefulness of DNA metabarcoding in diet studies and the detection of GZP, which are rapidly digested and due to that often overlooked with traditional methods. Furthermore, I aimed to investigate the role of GZP species in the marine food web, which was investigated using stable isotope analysis, to determine the trophic level of GZP and fish species in Porsangerfjorden. Overall, I was able to show that GZP was consumed regularly by many predators in the Arctic and sub-Arctic seas during different seasons. Furthermore, I showed that GZP should be considered as different groups in food web models rather than being pooled into one term.