TY - JOUR
T1 - Spring succession and vertical export of diatoms and IP25 in a seasonally ice-covered high arctic fjord
AU - Limoges, Audrey
AU - Massé, Guillaume
AU - Weckström, Kaarina
AU - Poulin, Michel
AU - Ellegaard, Marianne
AU - Heikkilä, Maija
AU - Geilfus, Nicolas Xavier
AU - Sejr, Mikael K.
AU - Rysgaard, Søren
AU - Ribeiro, Sofia
N1 - Publisher Copyright:
© Copyright © 2018 Limoges, Massé, Weckström, Poulin, Ellegaard, Heikkilä, Geilfus, Sejr, Rysgaard and Ribeiro.
PY - 2018/12/13
Y1 - 2018/12/13
N2 - The biomarker IP25 and fossil diatom assemblages preserved in
seafloor sediments are commonly used as proxies for paleo Arctic
sea-ice reconstructions, but how their production varies over the
seasons and is exported to the sediment remains unclear. We analyzed IP25
concentrations and diatom assemblages from a 5-week consecutive series
of sea-ice cores and compared the results with sediment trap and surface
sediment samples collected at the same site in the Young Sound fjord,
Northeast Greenland. Our aim was to investigate the dynamics of diatom
colonization of the spring sea ice and the in situ production of IP25.
Additionally, selected diatom taxa observed in the sea-ice samples were
isolated from in-ice assemblages and their lipid composition was
analyzed via gas chromatography-mass spectrometry. We confirm that Haslea spicula (and not the closely related species H. crucigeroides) is an IP25-producer. All three known IP25-producing taxa (Haslea spicula, H. kjellmanii, and Pleurosigma stuxbergii var. rhomboides) were present in Young Sound sea-ice and the low IP25 concentrations measured in the sea-ice (0.44–0.72 pg mL−1) were consistent with the low abundance of these source species (0.21–9.66 valves mL−1). Total sympagic diatom production also remained very low (21–985 valves mL−1),
suggesting that the fjord's sea ice did not provide an optimal
physical-chemical environment for diatoms to thrive. Temporal changes in
the sympagic diatom community were also observed, with an early
presence of the pelagic Thalassiosira hyperborea and subsequent dominance of pennate taxa, including Nitzschia and Navicula species, Fossula arctica and Stauronella arctica. The assemblages observed during and after the seasonal ice melt consisted primarily of Fossula arctica, Fragilariopsis oceanica, Thalassiosira antarctica var. borealis (resting spores), and Chaetoceros
spp. (vegetative cells and resting spores). The seafloor sediment
assemblages largely reflected the melt and post-melt planktic production
and were dominated by the resting spores of the centric Chaetoceros spp. and Thalassiosira antarctica var. borealis, and the pennate Fragilariopsis oceanica, Fossula arctica, and Fragilariopsis reginae-jahniae. This study documents that IP25
is produced in Young Sound, and that the weak fingerprint of sea ice in
the sediment appears to be primarily due to the limited sea-ice diatom
biomass.
AB - The biomarker IP25 and fossil diatom assemblages preserved in
seafloor sediments are commonly used as proxies for paleo Arctic
sea-ice reconstructions, but how their production varies over the
seasons and is exported to the sediment remains unclear. We analyzed IP25
concentrations and diatom assemblages from a 5-week consecutive series
of sea-ice cores and compared the results with sediment trap and surface
sediment samples collected at the same site in the Young Sound fjord,
Northeast Greenland. Our aim was to investigate the dynamics of diatom
colonization of the spring sea ice and the in situ production of IP25.
Additionally, selected diatom taxa observed in the sea-ice samples were
isolated from in-ice assemblages and their lipid composition was
analyzed via gas chromatography-mass spectrometry. We confirm that Haslea spicula (and not the closely related species H. crucigeroides) is an IP25-producer. All three known IP25-producing taxa (Haslea spicula, H. kjellmanii, and Pleurosigma stuxbergii var. rhomboides) were present in Young Sound sea-ice and the low IP25 concentrations measured in the sea-ice (0.44–0.72 pg mL−1) were consistent with the low abundance of these source species (0.21–9.66 valves mL−1). Total sympagic diatom production also remained very low (21–985 valves mL−1),
suggesting that the fjord's sea ice did not provide an optimal
physical-chemical environment for diatoms to thrive. Temporal changes in
the sympagic diatom community were also observed, with an early
presence of the pelagic Thalassiosira hyperborea and subsequent dominance of pennate taxa, including Nitzschia and Navicula species, Fossula arctica and Stauronella arctica. The assemblages observed during and after the seasonal ice melt consisted primarily of Fossula arctica, Fragilariopsis oceanica, Thalassiosira antarctica var. borealis (resting spores), and Chaetoceros
spp. (vegetative cells and resting spores). The seafloor sediment
assemblages largely reflected the melt and post-melt planktic production
and were dominated by the resting spores of the centric Chaetoceros spp. and Thalassiosira antarctica var. borealis, and the pennate Fragilariopsis oceanica, Fossula arctica, and Fragilariopsis reginae-jahniae. This study documents that IP25
is produced in Young Sound, and that the weak fingerprint of sea ice in
the sediment appears to be primarily due to the limited sea-ice diatom
biomass.
KW - Arctic sea-ice
KW - climate change
KW - climate proxy
KW - diatoms
KW - HBIs
KW - Northeast Greenland
KW - paleoenvironmental reconstructions
UR - http://www.scopus.com/inward/record.url?scp=85080985372&partnerID=8YFLogxK
U2 - 10.3389/feart.2018.00226
DO - 10.3389/feart.2018.00226
M3 - Article
SN - 2296-6463
VL - 6
JO - Frontiers in Earth Science
JF - Frontiers in Earth Science
M1 - 226
ER -