TY - JOUR

T1 - An annual cycle of diatom succession in two contrasting Greenlandic fjords

T2 - from simple sea-ice indicators to varied seasonal strategists

AU - Luostarinen, Tiia

AU - Ribeiro, Sofia

AU - Weckström, Kaarina

AU - Sejr, Mikael

AU - Meire, Lorenz

AU - Tallberg, Petra

AU - Heikkilä, Maija

N1 - Funding Information: This study was funded by the Academy of Finland (project no. 307282 and no. 296895) and GEOCENTER Danmark (project GreenShift). The time series data were collected by the MarineBasis–Zackenberg marine climate monitoring programme, and MarineBasis Nuuk monitoring program, part of Greenland Ecosystem Monitoring programme (g-e-m.dk). L.M. was funded by research programme VENI with project number 016.Veni.192.150 from the Dutch Research Council (NWO). We thank editors and two anonymous reviewers for their comments that greatly improved the manuscript. We also thank Annette Ryge, Charlotte Olsen, Kitte Linding Gerlich, Heini Ali-Kovero and Meeri Näppilä for help with the sample preparation and analyses. We acknowledge the use of imagery from the NASA Worldview application (https://worldview.earthdata.nasa.gov), part of the NASA Earth Observing System Data and Information System (EOSDIS). Funding Information: This study was funded by the Academy of Finland (project no. 307282 and no. 296895 ) and GEOCENTER Danmark (project GreenShift). The time series data were collected by the MarineBasis–Zackenberg marine climate monitoring programme, and MarineBasis Nuuk monitoring program, part of Greenland Ecosystem Monitoring programme (g-e-m.dk). L.M. was funded by research programme VENI with project number 016.Veni.192.150 from the Dutch Research Council (NWO). We thank editors and two anonymous reviewers for their comments that greatly improved the manuscript. We also thank Annette Ryge, Charlotte Olsen, Kitte Linding Gerlich, Heini Ali-Kovero and Meeri Näppilä for help with the sample preparation and analyses. We acknowledge the use of imagery from the NASA Worldview application ( https://worldview.earthdata.nasa.gov ), part of the NASA Earth Observing System Data and Information System (EOSDIS). Publisher Copyright: © 2020 Elsevier B.V.

PY - 2020

Y1 - 2020

N2 - 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 Godthåbsfjord in subarctic Southwest Greenland. The traps were positioned at differing water depths (37 m in Young Sound vs. 300 m in Godthåbsfjord). 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 × 106 valves m−2 d−1 in the spring. In Godthåbsfjord, total diatom flux was more stable throughout the year, with a maximum of 320 × 106 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 Godthåbsfjord, 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.

AB - 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 Godthåbsfjord in subarctic Southwest Greenland. The traps were positioned at differing water depths (37 m in Young Sound vs. 300 m in Godthåbsfjord). 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 × 106 valves m−2 d−1 in the spring. In Godthåbsfjord, total diatom flux was more stable throughout the year, with a maximum of 320 × 106 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 Godthåbsfjord, 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.

KW - Arctic

KW - Diatom

KW - Fjord

KW - Godthåbsfjord

KW - Northeast Greenland

KW - Palaeoceanography

KW - Sea ice

KW - Seasonal

KW - Sediment trap

KW - Southwest Greenland

KW - Young Sound

U2 - 10.1016/j.marmicro.2020.101873

DO - 10.1016/j.marmicro.2020.101873

M3 - Journal article

AN - SCOPUS:85086827913

VL - 158

JO - Marine Micropaleontology

JF - Marine Micropaleontology

SN - 0377-8398

M1 - 101873

ER -