An annual cycle of diatom succession in two contrasting Greenlandic fjords : from simple sea-ice indicators to varied seasonal strategists

• Published in: Marine Micropaleontology
• Main Authors: Luostarinen, Tiia, Ribeiro, Sofia, Weckstrom, Kaarina, Sejr, Mikael, Meire, Lorenz, Tallberg, Petra, Heikkila, Maija
• Other Authors: Ecosystems and Environment Research Programme, Helsinki Institute of Sustainability Science (HELSUS), Environmental Change Research Unit (ECRU), Biosciences, Marine Ecosystems Research Group
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Scientific Publ. Co 2022
• Subjects: Diatom; Seasonal; Sea ice; Sediment trap; Arctic; Palaeoceanography; Fjord; Northeast Greenland; Southwest Greenland; Godthabsfjord; Young Sound; WEST GREENLAND; BIOGENIC SILICA; EXPORT FLUXES; VARIABILITY; OCEAN; NORTH; ICELAND; RECORD; 1181 Ecology; evolutionary biology; Greenland; Antarc*; Antarctica; greenlandic; Iceland; Subarctic
• Online Access: http://hdl.handle.net/10138/343977

We recorded diatom species succession over one full year (May 2017-May 2018) using automated sediment traps installed in two contrasting Greenlandic fjords: the seasonally ice-covered Young Sound in high-arctic Northeast Greenland and the nearly sea-ice free Godthabsfjord in subarctic Southwest Greenland. The traps were positioned at differing water depths (37m in Young Sound vs. 300m in Godthabsfjord). Distinct differences between the study sites were observed in both sediment and diatom fluxes. In Young Sound, total diatom flux was extremely seasonal and as high as 880 x 10(6) valves m(-2) d(-1) in the spring. In Godthabsfjord, total diatom flux was more stable throughout the year, with a maximum of 320 x 10(6) valves m(-2) d(-1) in the summer. The diatom assemblage in Young Sound was dominated by the sea-ice species Fragilariopsis oceanica, Fragilariopsis reginae-jahniae and Fossula arctica, which exhibited pulse-like deposition in the trap during and after the ice melt. In Godthabsfjord, the fluxes were dominated by Chaetoceros (resting spores), while the remaining assemblage was characterised by the cold-water indicator species Detonula confervacea (resting spores) and Thalassiosira antarctica var. borealis (resting spores) together with Fragilariopsis cylindrus. Our data show that, F. oceanica, F. reginae-jahniae and F. arctica exhibit similar seasonal behaviour and a clear link to sea ice. Fragilariopsis cylindrus seems to have a more flexible niche, and based on our study, cannot be considered an unequivocal ice indicator. Taking into account these ecological and seasonal preferences of individual diatom species is crucial when reconstructing past sea-ice conditions both qualitatively and quantitatively. Peer reviewed