Preprints
https://doi.org/10.5194/bg-2022-237
https://doi.org/10.5194/bg-2022-237
 
14 Dec 2022
14 Dec 2022
Status: this preprint is currently under review for the journal BG.

Iron “Ore” Nothing: Benthic iron fluxes from the oxygen-deficient Santa Barbara Basin enhance phytoplankton productivity in surface waters

De’Marcus Robinson1, Anh L. D. Pham1, David J. Yousavich2, Felix Janssen3, Frank Wenzhöfer3, Eleanor C. Arrington4, Kelsey M. Gosselin5, Marco Sandoval-Belmar1, Matthew Mar1, David L. Valentine4, Daniele Bianchi1, and Tina Treude1,2 De’Marcus Robinson et al.
  • 1Department of Atmospheric and Oceanic Sciences, University of California Los Angeles, Los Angeles, CA, USA
  • 2Department of Earth, Planetary, and Space Sciences, University of California Los Angeles, Los Angeles, CA, USA
  • 3HGF-MPG Joint Research Group for Deep-Sea Ecology and Technology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 4Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106, USA
  • 5Interepartment Graduate Program in Marine Science, University of California, Santa Barbara, CA 93106, USA

Abstract. The trace metal iron (Fe) is an essential micronutrient that controls phytoplankton productivity, which subsequently affects the cycling of macronutrients. Along the continental margin of the U.S. West Coast, high benthic Fe release has been documented, in particular from deep anoxic basins in the Southern California Borderland. However, the influence of this Fe release on surface primary production remains poorly understood. In the present study from the Santa Barbara Basin, in-situ benthic Fe fluxes were determined along a transect from shallow to deep sites in the basin. Fluxes ranged between 0.23 and 4.9 mmol m-2 d-1, representing some of the highest benthic Fe fluxes reported to date. To investigate the influence of benthic Fe release from the oxygen-deficient deep basin on surface phytoplankton production, we combined benthic flux measurements with numerical simulations using the Regional Ocean Model System coupled to the Biogeochemical Elemental Cycling model (ROMS-BEC). For this purpose, we updated existing Fe flux parameterization to include new benthic fluxes from the Santa Barbara Basin. Our simulation suggests benthic iron fluxes support surface primary production creating positive feedback on benthic Fe release by enhancing low oxygen conditions in bottom waters. However, the easing of phytoplankton Fe limitation near the coast may be partially compensated by increased nitrogen limitation further offshore, reducing the efficacy of this positive feedback.

De’Marcus Robinson et al.

Status: open (until 25 Feb 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • AC1: 'Comment on bg-2022-237', Tina Treude, 17 Dec 2022 reply
  • RC1: 'Comment on bg-2022-237', Christopher Somes, 13 Jan 2023 reply

De’Marcus Robinson et al.

De’Marcus Robinson et al.

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Short summary
The present study suggests that high release of ferrous iron from the seafloor of the oxygen-deficient Santa Barabara Basin (California) supports surface primary productivity, creating positive feedback on seafloor iron release by enhancing low oxygen conditions in the basin.
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