The role of sea ice algae-produced carbon in Arctic and Antarctic food webs. Dependency of polar life on a threatened food source

• Main Author: Kohlbach, Doreen
• Format: Thesis
• Language: unknown
• Published: University of Hamburg 2017
• Subjects: Antarc*; Antarctic; Arctic; Arctic Ocean; ice algae; Ice Shelf; Sea ice; Southern Ocean; Weddell Sea; Zooplankton; Copepods
• Online Access: https://epic.awi.de/id/eprint/52366/; https://epic.awi.de/id/eprint/52366/1/Thesis_Kohlbach_submitted.pdf; https://hdl.handle.net/10013/epic.d77c6021-d51a-419e-9c18-6e290c66e760

The underside of sea ice in Polar Regions represents a natural habitat for heterotrophic organisms, such as copepods and amphipods. This under-ice fauna plays a key role in transferring carbon synthesized by sea ice-associated (sympagic) microalgae into associated pelagic and benthic food webs of polar ecosystems. Animals at higher trophic levels are adapted to feed on the under-ice fauna as well as on pelagic zooplankton and nekton. Polar ecosystems thrive significantly on ice algae-produced carbon depending on different periods of the year. Thus, the under-ice fauna and the associated pelagic food web are largely affected by multi-scale climate changes accompanied by the reduction of sea ice coverage and an increasing duration of the melt season. Until now, however, the degree to which polar food webs depend on sea ice-derived carbon is unclear. The overall aim of this thesis is to quantify the transfer of ice algae-produced carbon from the sea ice into the under-ice community and from there into pelagic food webs in Arctic and Antarctic ecosystems, in order to improve our understanding of the potential ecological consequences of a changing sea ice environment for marine food web dynamics. Furthermore, spatial and seasonal differences in the utilization of ice algaeproduced carbon within and between both hemispheres are investigated. The sample collection in the central Arctic Ocean was carried out during the RV ‘Polarstern’ expedition ARK XXVII-3 (PS80, August-September 2012) within the Amundsen and Nansen Basins. In the Southern Ocean, samples were collected during the RV ‘Polarstern’ expeditions ANT XXIX-7 (PS81, August-October 2013) in the northern Weddell Sea and ANT XXIX-9 (PS82, December 2013-March 2014) offshore from the Filchner Ice Shelf. Trophic interactions of important representatives of Arctic and Antarctic food webs are studied using lipid fingerprinting, stable isotope analysis (SIA) of natural abundance bulk carbon and nitrogen (BSIA), and compound-specific SIA (CSIA) of fatty acids (FAs). ...