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Nutrient and Silicon Isotope Dynamics in the Laptev Sea and Implications for Nutrient Availability in the Transpolar Drift

Laukert, G. ; Grasse, P. ; Novikhin, A. ; Povazhnyi, V. ; Doering, K. LU orcid ; Hölemann, J. ; Janout, M. ; Bauch, D. ; Kassens, H. and Frank, M. (2022) In Global Biogeochemical Cycles 36(9).
Abstract

Realistic prediction of the near-future response of Arctic Ocean primary productivity to ongoing warming and sea ice loss requires a mechanistic understanding of the processes controlling nutrient bioavailability. To evaluate continental nutrient inputs, biological utilization, and the influence of mixing and winter processes in the Laptev Sea, the major source region of the Transpolar Drift (TPD), we compare observed with preformed concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP), silicic acid (DSi), and silicon isotope compositions of DSi (δ30SiDSi) obtained for two summers (2013 and 2014) and one winter (2012). In summer, preformed nutrient concentrations persisted in the surface layer... (More)

Realistic prediction of the near-future response of Arctic Ocean primary productivity to ongoing warming and sea ice loss requires a mechanistic understanding of the processes controlling nutrient bioavailability. To evaluate continental nutrient inputs, biological utilization, and the influence of mixing and winter processes in the Laptev Sea, the major source region of the Transpolar Drift (TPD), we compare observed with preformed concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP), silicic acid (DSi), and silicon isotope compositions of DSi (δ30SiDSi) obtained for two summers (2013 and 2014) and one winter (2012). In summer, preformed nutrient concentrations persisted in the surface layer of the southeastern Laptev Sea, while diatom-dominated utilization caused intense northward drawdown and a pronounced shift in δ30SiDSi from +0.91 to +3.82‰. The modeled Si isotope fractionation suggests that DSi in the northern Laptev Sea originated from the Lena River and was supplied during the spring freshet, while riverine DSi in the southeastern Laptev Sea was continuously supplied during the summer. Primary productivity fueled by river-borne nutrients was enhanced by admixture of DIN- and DIP-rich Atlantic-sourced waters to the surface, either by convective mixing during the previous winter or by occasional storm-induced stratification breakdowns in late summer. Substantial enrichments of DSi (+240%) and DIP (+90%) beneath the Lena River plume were caused by sea ice-driven redistribution and remineralization. Predicted weaker stratification on the outer Laptev Shelf will enhance DSi utilization and removal through greater vertical DIN supply, which will limit DSi export and reduce diatom-dominated primary productivity in the TPD.

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organization
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type
Contribution to journal
publication status
published
subject
keywords
Arctic Ocean, diatoms, Laptev Sea, nutrients, silicon isotopes, transpolar drift
in
Global Biogeochemical Cycles
volume
36
issue
9
article number
e2022GB007316
publisher
American Geophysical Union (AGU)
external identifiers
  • scopus:85138897476
ISSN
0886-6236
DOI
10.1029/2022GB007316
language
English
LU publication?
yes
additional info
Funding Information: We like to thank the Captain and Crew of the RV Viktor Buynitskiy and all members of the project “Laptev Sea System” for their help in collecting and transporting the samples. We also acknowledge Jutta Heinze and Andre Mutzberg (GEOMAR) for laboratory assistance and DSi analysis in the isotope samples, respectively. Financial support for the “Laptev Sea System” project was provided by the German Federal Ministry of Education and Research (Grant BMBF 03F0776 and 03G0833) and the Ministry of Education and Science of the Russian Federation. G. L. also acknowledges financial support through the Ocean Frontier Institute through an award from the Canada First Research Excellence Fund. Open Access funding enabled and organized by Projekt DEAL. Funding Information: We like to thank the Captain and Crew of the RV Viktor Buynitskiy and all members of the project “Laptev Sea System” for their help in collecting and transporting the samples. We also acknowledge Jutta Heinze and Andre Mutzberg (GEOMAR) for laboratory assistance and DSi analysis in the isotope samples, respectively. Financial support for the “Laptev Sea System” project was provided by the German Federal Ministry of Education and Research (Grant BMBF 03F0776 and 03G0833) and the Ministry of Education and Science of the Russian Federation. G. L. also acknowledges financial support through the Ocean Frontier Institute through an award from the Canada First Research Excellence Fund. Open Access funding enabled and organized by Projekt DEAL. Publisher Copyright: © 2022. The Authors.
id
22199837-848c-4390-9373-71506fa8af4b
date added to LUP
2022-10-17 16:17:06
date last changed
2022-10-28 15:18:21
@article{22199837-848c-4390-9373-71506fa8af4b,
  abstract     = {{<p>Realistic prediction of the near-future response of Arctic Ocean primary productivity to ongoing warming and sea ice loss requires a mechanistic understanding of the processes controlling nutrient bioavailability. To evaluate continental nutrient inputs, biological utilization, and the influence of mixing and winter processes in the Laptev Sea, the major source region of the Transpolar Drift (TPD), we compare observed with preformed concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP), silicic acid (DSi), and silicon isotope compositions of DSi (δ<sup>30</sup>Si<sub>DSi</sub>) obtained for two summers (2013 and 2014) and one winter (2012). In summer, preformed nutrient concentrations persisted in the surface layer of the southeastern Laptev Sea, while diatom-dominated utilization caused intense northward drawdown and a pronounced shift in δ<sup>30</sup>Si<sub>DSi</sub> from +0.91 to +3.82‰. The modeled Si isotope fractionation suggests that DSi in the northern Laptev Sea originated from the Lena River and was supplied during the spring freshet, while riverine DSi in the southeastern Laptev Sea was continuously supplied during the summer. Primary productivity fueled by river-borne nutrients was enhanced by admixture of DIN- and DIP-rich Atlantic-sourced waters to the surface, either by convective mixing during the previous winter or by occasional storm-induced stratification breakdowns in late summer. Substantial enrichments of DSi (+240%) and DIP (+90%) beneath the Lena River plume were caused by sea ice-driven redistribution and remineralization. Predicted weaker stratification on the outer Laptev Shelf will enhance DSi utilization and removal through greater vertical DIN supply, which will limit DSi export and reduce diatom-dominated primary productivity in the TPD.</p>}},
  author       = {{Laukert, G. and Grasse, P. and Novikhin, A. and Povazhnyi, V. and Doering, K. and Hölemann, J. and Janout, M. and Bauch, D. and Kassens, H. and Frank, M.}},
  issn         = {{0886-6236}},
  keywords     = {{Arctic Ocean; diatoms; Laptev Sea; nutrients; silicon isotopes; transpolar drift}},
  language     = {{eng}},
  number       = {{9}},
  publisher    = {{American Geophysical Union (AGU)}},
  series       = {{Global Biogeochemical Cycles}},
  title        = {{Nutrient and Silicon Isotope Dynamics in the Laptev Sea and Implications for Nutrient Availability in the Transpolar Drift}},
  url          = {{http://dx.doi.org/10.1029/2022GB007316}},
  doi          = {{10.1029/2022GB007316}},
  volume       = {{36}},
  year         = {{2022}},
}