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Christof Pearce

Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves: Contrasts in suspended particle composition

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  • Tommaso Tesi, Stockholm University, ISMAR-CNR
  • ,
  • Marc C. Geibel, Stockholm University
  • ,
  • Christof Pearce
  • Elena Panova, Tomsk National Research Polytechnic University
  • ,
  • Jorien E. Vonk, Vrije Universiteit Amsterdam
  • ,
  • Emma Karlsson, Stockholm University
  • ,
  • A. Joan Salvado, Stockholm University
  • ,
  • Martin Krusä, Stockholm University
  • ,
  • Lisa Bröder, Stockholm University
  • ,
  • Christoph Humborg, Stockholm University
  • ,
  • Igor Semiletov, Tomsk National Research Polytechnic University, Pacific Oceanological Institute, University of Alaska Fairbanks
  • ,
  • Örjan Gustafsson, Stockholm University

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 (> 10μm) 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 (< 10μm) dataset to understand the link between plankton composition and environmental conditions. ä13C and 114C exhibited a large variability in the POM (< 10μm) distribution while the content of terrestrial biomarkers in the POM was negligible. In the Laptev Sea (LS), (δ13C and Δ14C) of POM (< 10μm) 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 (< 10μm) 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.

Original languageEnglish
JournalOcean Science
Pages (from-to)735-748
Number of pages14
Publication statusPublished - 18 Sep 2017

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