Published September 18, 2017
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Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves: contrasts in suspended particle composition
Authors/Creators
- Tesi, T.1
- Tesi, T.2
- Tesi, T.3
- Geibel, M. C.1
- Geibel, M. C.2
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Pearce, C.2
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Pearce, C.4
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Pearce, C.5
- Panova, E.6
- Vonk, J. E.7
- Karlsson, E.1
- Karlsson, E.2
- Salvado, J. A.1
- Salvado, J. A.2
- Kruså, M.1
- Kruså, M.2
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Bröder, L.1
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Bröder, L.2
- Humborg, C.1
- Humborg, C.2
- Semiletov, I.6
- Semiletov, I.8
- Semiletov, I.9
- Gustafsson, Ö.1
- Gustafsson, Ö.2
- 1. Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, Stockholm, Sweden
- 2. Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
- 3. Institute of Marine Sciences, National Research Council (ISMAR-CNR), Bologna, Italy
- 4. Department of Geological Sciences, Stockholm University, Stockholm, Sweden
- 5. Department of Geoscience, Aarhus University, Aarhus, Denmark
- 6. Tomsk Polytechnic University, Tomsk, Russia
- 7. Vrije Universiteit Amsterdam (VU), Amsterdam, the Netherlands
- 8. Pacific Oceanological Institute FEB RAS, Vladivostok, Russia
- 9. University of Alaska Fairbanks, Fairbanks, USA
Description
Recent Arctic studies suggest that sea ice decline and permafrost
thawing will affect phytoplankton dynamics and stimulate heterotrophic
communities. However, in what way the plankton composition will change as the
warming proceeds remains elusive. Here we investigate the chemical signature
of the plankton-dominated fraction of particulate organic matter (POM) collected along the Siberian Shelf. POM
(> 10 µm) samples were analysed using molecular
biomarkers (CuO oxidation and IP25) and dual-carbon isotopes
(δ13C and Δ14C). In addition, surface water chemical
properties were integrated with the POM (> 10 µm)
dataset to understand the link between plankton composition and environmental
conditions.
δ13C and Δ14C exhibited a large variability in the POM (> 10 µm) distribution while the content of terrestrial biomarkers in the POM was negligible. In the Laptev Sea (LS), δ13C and Δ14C of POM (> 10 µm) suggested a heterotrophic environment in which dissolved organic carbon (DOC) from the Lena River was the primary source of metabolisable carbon. Within the Lena plume, terrestrial DOC probably became part of the food web via bacteria uptake and subsequently transferred to relatively other heterotrophic communities (e.g. dinoflagellates). Moving eastwards toward the sea-ice-dominated East Siberian Sea (ESS), the system became progressively more autotrophic. Comparison between δ13C of POM (> 10 µm) samples and CO2aq concentrations revealed that the carbon isotope fractionation increased moving towards the easternmost and most productive stations.
In a warming scenario characterised by enhanced terrestrial DOC release (thawing permafrost) and progressive sea ice decline, heterotrophic conditions might persist in the LS while the nutrient-rich Pacific inflow will likely stimulate greater primary productivity in the ESS. The contrasting trophic conditions will result in a sharp gradient in δ13C between the LS and ESS, similar to what is documented in our semi-synoptic study.
δ13C and Δ14C exhibited a large variability in the POM (> 10 µm) distribution while the content of terrestrial biomarkers in the POM was negligible. In the Laptev Sea (LS), δ13C and Δ14C of POM (> 10 µm) suggested a heterotrophic environment in which dissolved organic carbon (DOC) from the Lena River was the primary source of metabolisable carbon. Within the Lena plume, terrestrial DOC probably became part of the food web via bacteria uptake and subsequently transferred to relatively other heterotrophic communities (e.g. dinoflagellates). Moving eastwards toward the sea-ice-dominated East Siberian Sea (ESS), the system became progressively more autotrophic. Comparison between δ13C of POM (> 10 µm) samples and CO2aq concentrations revealed that the carbon isotope fractionation increased moving towards the easternmost and most productive stations.
In a warming scenario characterised by enhanced terrestrial DOC release (thawing permafrost) and progressive sea ice decline, heterotrophic conditions might persist in the LS while the nutrient-rich Pacific inflow will likely stimulate greater primary productivity in the ESS. The contrasting trophic conditions will result in a sharp gradient in δ13C between the LS and ESS, similar to what is documented in our semi-synoptic study.
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Additional details
Funding
- European Commission
- CC-TOP - Cryosphere-Carbon on Top of the Earth (CC-Top): Decreasing Uncertainties of Thawing Permafrost and Collapsing Methane Hydrates in the Arctic 695331
- European Commission
- ACTIVE PERMAFROST - Activation of old carbon from thawing permafrost in Arctic Siberia 328049
- European Commission
- ARCTIC - Sources, transport, and degradation of permafrost-derived organic carbon in a warming Arctic: the Siberian Shelf 300259