Arctic | Lower Trophic Levels
What we do in the shadows: Biochemical tracer methods suggest Arctic zooplankton feeding activity during polar night Presenter: Erin Kunisch , erin.kunisch@uit.no, UiT The Arctic University of Norway
Martin Graeve , martin.graeve@awi.de Rolf Gradinger , rolf.gradinger@uit.no Hauke Flores , hauke.flores@awi.de Øystein Varpe , øystein.varpe@uib.no Bodil Bluhm , bodil.bluhm@uit.no
During the productive polar day, the critical role of zooplankton and sea-ice amphipods have in energy transfer from primary producers to higher trophic-level species in Arctic marine ecosystems is well studied. Although recent polar night studies demonstrated higher levels of zooplankton and sea-ice amphipod activity than previously assumed, it is unknown if these invertebrates maintain polar night activity on stored lipids, opportunistic feeding, or a combination of both. To assess how zooplankton and sea-ice amphipods support themselves on seasonally varying resources, we studied their lipid classes, fatty acid compositions, and compound-specific stable isotopes of trophic biomarker fatty acids during polar day (June/July) and polar night (January). Lipid storage and fatty acid results confirm previously described dietary sources in all species during polar day. We found storage investments into both neutral and polar lipids, and fatty acid biomarker analysis demonstrated diatom and dinoflagellate dietary support for herbivorous and omnivorous species. However, we also found evidence of polar night feeding activity in all species, including shifts in nutrition from primary producers to other food sources. Sympagic-, pelagic-, and Calanus spp .-derived carbon sources supported zooplankton and sea-ice amphipods in both seasons. We provide the first evidence on polar night feeding of sea-ice amphipods in the pelagic realm and further suggest that the notion of polar night as a dormant phase should be phased out in the Atlantic inflow region to the Arctic Ocean.
Alaska Marine Science Symposium 2023 148
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