FN Archimer Export Format PT J TI The contrasted phytoplankton dynamics across a frontal system in the southwestern Mediterranean Sea BT AF Tzortzis, Roxane Doglioli, Andrea M. Barrillon, Stéphanie Petrenko, Anne A. Izard, Lloyd Zhao, Yuan d'Ovidio, Francesco Dumas, Franck Gregori, Gérald AS 1:1;2:1;3:1;4:1;5:2;6:3;7:2;8:4;9:1; FF 1:;2:;3:;4:;5:;6:;7:;8:;9:; C1 Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d’Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN-IPSL), Paris, France CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, People’s Republic of China SHOM, Service Hydrographique et Océanographique de la Marine, 13 rue de Chatellier, CS592803, 29228 Brest, CEDEX 2, France C2 UNIV AIX MARSEILLE, FRANCE UNIV SORBONNE, FRANCE CHINESE ACAD SCI, CHINA SHOM, FRANCE IF 4.9 TC 0 UR https://archimer.ifremer.fr/doc/00797/90906/96572.pdf https://archimer.ifremer.fr/doc/00797/90906/104212.pdf LA English DT Article CR PROTEVSMED_SWOT_2018_LEG1 PROTEVSMED_SWOT_2018_LEG2 BO Beautemps-Beaupré AB 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. PY 2023 PD AUG SO Biogeosciences SN 1726-4170 PU Copernicus GmbH VL 20 IS 16 UT 001052147100001 BP 3491 EP 3508 DI 10.5194/bg-20-3491-2023 ID 90906 ER EF