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 Robinson, Anh L. D. Pham, David J. Yousavich, Felix Janssen, Frank Wenzhöfer, Eleanor C. Arrington, Kelsey M. Gosselin, Marco Sandoval-Belmar, Matthew Mar, David L. Valentine, Daniele Bianchi, and Tina Treude

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: final response (author comments only)

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
  • RC1: 'Comment on bg-2022-237', Christopher Somes, 13 Jan 2023
    • AC2: 'Reply on RC1', Tina Treude, 10 Aug 2023
  • RC2: 'Comment on bg-2022-237', Anonymous Referee #2, 20 Mar 2023
    • AC3: 'Reply on RC2', Tina Treude, 10 Aug 2023

De’Marcus Robinson et al.

De’Marcus Robinson et al.


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Latest update: 10 Aug 2023
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.