10 Oct 2022
10 Oct 2022
Status: this preprint is open for discussion.

The contrasted phytoplankton dynamics across a frontal system in the southwestern Mediterranean Sea

Roxane Tzortzis1, Andrea M. Doglioli1, Stéphanie Barrillon1, Anne A. Petrenko1, Lloyd Izard2, Yuan Zhao3, Francesco d'Ovidio2, Franck Dumas4, and Gérald Gregori1 Roxane Tzortzis et al.
  • 1Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
  • 2Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d’Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN-IPSL), Paris, France
  • 3CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
  • 4SHOM, Service Hydrographique et Océanographique de la Marine, 13 rue de Chatellier, CS592803, 29228 Brest, CEDEX 2, France

Abstract. Phytoplankton plays a major role in the ocean, being the basis of the marine food web and controlling the biogeochemical cycles. Numerical simulation have shown that finescale structures such as fronts are often suitable places for the generation of vertical velocities, transporting subsurface nutrients to the euphotic zone and thus modulating phytoplankton abundance and community structure. Since several years, observations have concentrated on nutrient fluxes along these structures. Instead, direct in situ estimations of the phytoplankton growth rates are much less numerous; although difficult to obtain, they provide a precious information on the ecosystem functioning. Here, we consider the case of a front separating two water masses characterized by several phytoplankton groups with different abundances, in the southwestern Mediterranean Sea. In order to estimate possible differences in growing rates, we used an adaptive and Lagrangian sampling strategy to measure the phytoplankton diurnal cycle in these two water masses. The use of a size-structured population model was then applied to these data to estimate the growth and division rates for each phytoplankton groups identified by flow cytometry, showing that these two population parameters are significantly different on the two sides of the front, and consistent with the relative abundances. Our results introduce a general method for estimating growth rates at frontal systems, paving the way to in situ exploration of finescale biophysical scenarios.

Roxane Tzortzis et al.

Status: open (until 02 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-1008', Anonymous Referee #1, 23 Nov 2022 reply
    • AC1: 'Reply on RC1', Roxane Tzortzis, 25 Nov 2022 reply

Roxane Tzortzis et al.

Data sets

PROTEVS-MED field experiments: Very High Resolution Hydrographic Surveys in the Western Mediterranean Sea Dumas Franck, Garreau Pierre, Louazel Stephanie, Correard Stephanie, Fercoq Solenn, Le Menn Marc, Serpette Alain, Garnier Valerie, Stegner Alexandre, Le Vu Briac, Doglioli Andrea, Gregori Gerald

Roxane Tzortzis et al.


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Short summary
We studied a finescale frontal structure in order to highlight its influence on the dynamics and distribution of the phytoplankton communities. We computed the growth rates of several phytoplankton groups identified by flow cytometry, in two water masses separated by the front. We found contrasted phytoplankton dynamics on the two sides of the front, consistent with the distribution of their abundances. Our study bring new insights on the physical and biological coupling in a finescale front.