Chkili O., Meddeb M., Kousri K. M., Garali S. M. B., Belkhahia N. M., Tedetti Marc, Pagano Marc, Zouari A. B., Belhassen M., Niquil N., Hlaili A. S. (2023). Influence of nutrient gradient on phytoplankton size structure, primary production and carbon transfer pathway in a highly productive area (SE Mediterranean). Ocean Science Journal, 58 (1), 6 [23 p.]. ISSN 1738-5261.
Titre du document
Influence of nutrient gradient on phytoplankton size structure, primary production and carbon transfer pathway in a highly productive area (SE Mediterranean)
Année de publication
2023
Auteurs
Chkili O., Meddeb M., Kousri K. M., Garali S. M. B., Belkhahia N. M., Tedetti Marc, Pagano Marc, Zouari A. B., Belhassen M., Niquil N., Hlaili A. S.
Source
Ocean Science Journal, 2023,
58 (1), 6 [23 p.] ISSN 1738-5261
We assessed the spatial variability in the size structure of phytoplankton, community composition, primary production and carbon fluxes through the planktonic food web of the Gulf of Gabes (GG; Southeastern Mediterranean Sea) in the fall of 2017 during the MERMEX-MERITE cruise. High concentrations in nutrients, chlorophyll a (similar to 2-6 mu g L-1) and primary production (1816-3674 mg C m(-2) d(-1)) revealed an eutrophic status of the studied stations in the GG. In accordance with hydrodynamic features, inorganic nutrients showed increases in concentrations from North to South and from coast to offshore, these nutrient gradients impacting the spatial distribution of phytoplankton community. Size-fractioned phytoplankton biomass and production were the lowest in the northernmost zone where they were mainly sustained by pico-sized fraction. Concomitantly, in this area, small aloricate ciliates were dominant leading to a high microbivory. Conversely, higher biomass and production were measured towards the South and offshore with prevalence of larger phytoplankton (nano- and/or micro-sized fractions) supported by diatoms. The herbivorous protozooplankton and metazooplankton were more abundant in these zones, resulting in an increase of the herbivory. The vertical particulate organic carbon flux followed also a north-south and coast-offshore increasing gradient, with a higher contribution of phytoplankton, and zooplankton fecal pellets to the sinking organic matter in the southernmost area. Our results suggest that even in nutrient-rich and highly productive waters, a continuum of trophic pathways, ranging from microbial to multivorous and herbivorous food webs, may exist, which implies different efficiencies in carbon export and carrying capacity within the ecosystem.
Plan de classement
Limnologie biologique / Océanographie biologique [034]
;
Ecologie, systèmes aquatiques [036]
Description Géographique
MEDITERRANEE ; TUNISIE
Localisation
Fonds IRD [F B010086858]
Identifiant IRD
fdi:010086858
