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The impact of zooplankton calcifiers on the marine carbon cycle
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  • Nielja S. Knecht,
  • Fabio Benedetti,
  • Urs Hofmann,
  • nina Bednaršek,
  • Sonia Chaabane,
  • Catharina de Weerd,
  • Katja Peijnenburg,
  • Ralf Schiebel,
  • Meike Vogt
Nielja S. Knecht
ETH Zurich

Corresponding Author:nknecht@ethz.ch

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Fabio Benedetti
Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, 8092, Zürich, Switzerland.
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Urs Hofmann
ETH Zurich
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nina Bednaršek
National Institute of Biology
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Sonia Chaabane
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Catharina de Weerd
Naturalis Biodiversity Center
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Katja Peijnenburg
Naturalis Biodiversity Center
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Ralf Schiebel
Max Planck Institute for Chemistry
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Meike Vogt
ETH Zuerich
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Shelled pteropods and planktic foraminifers are calcifying zooplankton that contribute to the biological carbon pump, but their importance for regional and global plankton biomass and carbon fluxes is not well understood. Here, we modelled global annual patterns of pteropod and foraminifer total carbon (TC) biomass and total inorganic carbon (TIC) export fluxes over the top 200m using an ensemble of five species distribution models (SDMs). An exhaustive newly assembled dataset of zooplankton abundance observations was used to estimate the biomass of both plankton groups. With the SDM ensemble we modeled global TC biomass depending on multiple environmental parameters. We found hotspots of mean annual pteropod biomass in the high Northern latitudes and the global upwelling systems, and in the high latitudes of both hemispheres and the tropics for foraminifers. This largely agrees with previously observed distributions. For the biomass of both groups, surface temperature is the strongest environmental correlate, followed by chlorophyll-a. We found mean annual standing stocks of 52 (48-57) Tg TC and 0.9 (0.6-1.1) Tg TC for pteropods and foraminifers, respectively. This translates to mean annual TIC fluxes of 14 (9-22) Tg TIC yr-1 for pteropod shells and 11 (3-27) Tg TIC yr-1 for foraminifer tests. These results are similar to previous estimates for foraminifers standing stocks and fluxes but approximately a factor of ten lower for pteropods. The two zooplankton calcifiers contribute approximately 1.5% each to global surface carbonate fluxes, leaving 40%-60% of the global carbonate fluxes unaccounted for. We make suggestions how to close this gap.
04 Jan 2023Submitted to ESS Open Archive
04 Jan 2023Published in ESS Open Archive