30 Nov 2022
30 Nov 2022

Including filter-feeding gelatinous macrozooplankton in a global marine biogeochemical model: model-data comparison and impact on the ocean carbon cycle

Corentin Clerc1, Laurent Bopp1, Fabio Benedetti2, Meike Vogt2, and Olivier Aumont3 Corentin Clerc et al.
  • 1LMD / IPSL, Ecole normale supérieure / Université PSL, CNRS, Ecole Polytechnique, Sorbonne Université, Paris, France
  • 2Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, 8092, Zürich, Switzerland
  • 3LOCEAN / IPSL, IRD, CNRS, Sorbonne Université, MNHN, Paris, France

Abstract. Filter-feeding gelatinous macrozooplankton (FFGM), namely salps, pyrosomes and doliolids, are increasingly recognized as an essential component of the marine ecosystem. Unlike crustacean zooplankton (e.g., copepods) that feed on preys that are an order of magnitude smaller, filter-feeding allows FFGM to have access to a wider range of organisms, with predator over prey ratios as high as 105 : 1. In addition, most FFGM produce carcasses and/or fecal pellets that sink 10 times faster than those of copepods. This implies a rapid and efficient export of organic matter to depth. Even if these organisms represent <5 % of the overall planktonic biomass, the induced organic matter flux could be substantial. Here we present a first estimate of the influence of FFGM organisms on the export of particulate organic matter to the deep ocean based on the marine biogeochemical model NEMO-PISCES. In this new version of PISCES, two processes characterize FFGM: the preference for small organisms due to filter feeding, and the rapid sinking of carcasses and fecal pellets. To evaluate our modeled FFGM distribution, we compiled FFGM abundance observations into a monthly biomass climatology using a taxon-specific conversion. A model-observation comparison supports the model ability to quantify the global and large-scale patterns of FFGM biomass distribution, but reveals an urgent need to better understand the factors triggering the boom-and-bust FFGM dynamics before we can reproduce the observed spatio-temporal variability of FFGM. FFGM contribute strongly to carbon export at depth (0.4 Pg C yr-1 at 1000 m), particularly in low-productivity region (up to 40 % of organic carbon export at 1000 m) where they dominate macrozooplankton by a factor of 2. The FFGM-induced export increases in importance with depth, with a simulated transfer efficiency close to one.

Corentin Clerc et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1282', Rebecca Wright, 06 Jan 2023
    • AC1: 'Reply on RC1', Corentin Clerc, 17 Jan 2023
  • RC2: 'Comment on egusphere-2022-1282', Anonymous Referee #2, 07 Jan 2023
    • AC2: 'Reply on RC2', Corentin Clerc, 17 Jan 2023

Corentin Clerc et al.

Corentin Clerc et al.


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Short summary
Gelatinous zooplankton play a key role in the ocean carbon cycle. In particular, pelagic tunicates, which feed on a wide size range of preys, produce rapidly sinking detritus. Thus, they efficiently transfer carbon from the surface to the depth. Consequently, we added these organisms to a marine biogeochemical model (PISCES-v2) and evaluated their impact on the global carbon cycle. We found that they contribute significantly to carbon export, and that this contribution increases with depth.