FN Archimer Export Format
PT J
TI Deep maxima of phytoplankton biomass, primary production and bacterial production in the Mediterranean Sea
BT 
AF Maranon, Emilio
   Van Vambeke, France
   Uitz, Julia
   Boss, Emmanuel S
   Dimier, Céline
   Dinasquet, Julie
   Engel, Anja
   Haentjens, Nils
   Perez-Lorenzo, Maria
   Taillandier, Vincent
   Zancker, Birthe
AS 1:1;2:2;3:3;4:4;5:3;6:5;7:6;8:4;9:1;10:3;11:6,7;
FF 1:;2:;3:;4:;5:;6:;7:;8:;9:;10:;11:;
C1 Department of Ecology and Animal Biology, Universidade de Vigo, 36310 Vigo, Spain
   Mediterranean Institute of Oceanography, Aix-Marseille Université, CNRS, Université de Toulon, CNRS, IRD, MIO UM 110, 13288 Marseille, France
   Laboratoire d'Océanographie de Villefranche, Sorbonne Université, CNRS, 06230 Villefranche-sur-Mer, France
   School of Marine Sciences, University of Maine, Orono, Maine, USA
   Scripps Institution of Oceanography, University of California, San Diego, San Diego, California, USA
   GEOMAR, Helmholtz Centre for Ocean Research Kiel, 24105 Kiel, Germany
   The Marine Biological Association of the United Kingdom, Plymouth, PL1 2PB, United Kingdom
C2 UNIV VIGO, SPAIN
   UNIV AIX MARSEILLE, FRANCE
   UNIV SORBONNE, FRANCE
   UNIV MAINE US, USA
   SCRIPPS INST OCEANOG, USA
   IFM GEOMAR, GERMANY
   MBA, UK
IN DOAJ
IF 5.092
TC 26
UR https://archimer.ifremer.fr/doc/00642/75454/76271.pdf
   https://archimer.ifremer.fr/doc/00642/75454/76272.pdf
   https://archimer.ifremer.fr/doc/00642/75454/83019.pdf
   https://archimer.ifremer.fr/doc/00642/75454/83020.pdf
LA English
DT Article
CR PEACETIME
BO Pourquoi pas ?
AB The deep chlorophyll maximum (DCM) is a ubiquitous feature of phytoplankton vertical distribution in stratified waters that is relevant to our understanding of the mechanisms that underpin the variability in photoautotroph ecophysiology across environmental gradients and has implications for remote sensing of aquatic productivity. During the PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea) cruise, carried out from 10 May to 11 June 2017, we obtained 23 concurrent vertical profiles of phytoplankton chlorophyll a, carbon biomass and primary production, as well as heterotrophic prokaryotic production, in the western and central Mediterranean basins. Our main aims were to quantify the relative role of photoacclimation and enhanced growth as underlying mechanisms of the DCM and to assess the trophic coupling between phytoplankton and heterotrophic prokaryotic production. We found that the DCM coincided with a maximum in both the biomass and primary production but not in the growth rate of phytoplankton, which averaged 0.3 d−1 and was relatively constant across the euphotic layer. Photoacclimation explained most of the increased chlorophyll a at the DCM, as the ratio of carbon to chlorophyll a (C:Chl a) decreased from ca. 90–100 (g:g) at the surface to 20–30 at the base of the euphotic layer, while phytoplankton carbon biomass increased from ca. 6 mg C m−3 at the surface to 10–15 mg C m−3 at the DCM. As a result of photoacclimation, there was an uncoupling between chlorophyll a-specific and carbon-specific productivity across the euphotic layer. The ratio of fucoxanthin to total chlorophyll a increased markedly with depth, suggesting an increased contribution of diatoms at the DCM. The increased biomass and carbon fixation at the base of the euphotic zone was associated with enhanced rates of heterotrophic prokaryotic activity, which also showed a surface peak linked with warmer temperatures. Considering the phytoplankton biomass and turnover rates measured at the DCM, nutrient diffusive fluxes across the nutricline were able to supply only a minor fraction of the photoautotroph nitrogen and phosphorus requirements. Thus the deep maxima in biomass and primary production were not fuelled by new nutrients but likely resulted from cell sinking from the upper layers in combination with the high photosynthetic efficiency of a diatom-rich, low-light acclimated community largely sustained by regenerated nutrients. Further studies with increased temporal and spatial resolution will be required to ascertain if the peaks of deep primary production associated with the DCM persist across the western and central Mediterranean Sea throughout the stratification season. 
PY 2021
PD MAR
SO Biogeosciences
SN 1726-4170
PU Copernicus GmbH
VL 18
IS 5
UT 000630062300001
BP 1749
EP 1767
DI 10.5194/bg-18-1749-2021
ID 75454
ER

EF