The characterisation and summer distribution of ultraphytoplankton in the Gulf of Gabes (Eastern Mediterranean Sea, Tunisia) by using flow cytometry - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Continental Shelf Research Année : 2015

The characterisation and summer distribution of ultraphytoplankton in the Gulf of Gabes (Eastern Mediterranean Sea, Tunisia) by using flow cytometry

I. Hamdi
  • Fonction : Auteur
Michel Denis
A. Bellaaj-Zouari
  • Fonction : Auteur
H. Khemakhem
  • Fonction : Auteur
M. Bel Hassen
  • Fonction : Auteur
A. Hamza
  • Fonction : Auteur
Aude Barani
Chantal Bezac
  • Fonction : Auteur
S. Maalej
  • Fonction : Auteur

Résumé

TheGulfofGabèsintheEasternMediterraneanBasinisoneofthelargestcontinentalshelvesandisahighly productivearea.ThisisincontrasttotheEasternMediterraneanBasinasawholewhichisoligotrophicto ultraoligotrophic.Overrecentyears,duetoincreasedpressurefromanthropologicalactivities,therehas beenadeclineinthebiologicalresourcesintheGulfofGabès.Thishasledscientiststofocustheirresearch on thedifferenttrophiclevelsofthefoodchainandinparticularonphytoplankton.Studiesdedicatedto phytoplanktonintheGulfofGabèshavepreviouslyreliedonconventionalglobalapproaches.Thisworkon theotherhand,examinesultraphytoplankton(o10 mm) distributionatthesinglecelllevelindifferent watermasses,duringasummercruise(2008).Threedistinctwatermasseswereidentified:modified Mediterraneanwaters(MMW),modified Atlanticwaters(MAW)andIonianwaters(IW).Despitethe summerperiod,nutrientswereabundantandnon-limiting.Flowcytometryresolved five cellgroups, Prochlorococcus, Synechococcus, picoeukaryotes,nanoeukaryotesandagroupofunidentified cells.These cellswerecharacterisedbylow fluorescencesignalsandscattersignalslargerthanthatofcyanobacteriaand picoeukaryotesandthuswerelabelledLFNanoforlow fluorescencenanoeukaryotes.Theywerefoundin veryhighabundances,whereastheotherusualgroupswererelativelylowinabundancedespitethe favourablegrowthconditions.LFNanofoundduringa2012summercruiseinthesamearea,werealso sorted by flowcytometryandobservedbyscanningelectronmicroscopy.Choanoflagellateswereidentified, andthesenanoflagellatesappeartoaccountforthelowabundanceintheusualultraphytoplanktongroup due totheirefficientfeeding/grazingmechanism.However,themostabundantLFNanocouldnotbe identified.Resultsstronglysuggestatop-downcontroloftheecosystem,consistentwiththehigh productivityoftheGulfthatimpliesarapidtransferofmatterandenergytohighertrophiclevels.
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Dates et versions

hal-01436533 , version 1 (16-01-2017)

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Citer

I. Hamdi, Michel Denis, A. Bellaaj-Zouari, H. Khemakhem, M. Bel Hassen, et al.. The characterisation and summer distribution of ultraphytoplankton in the Gulf of Gabes (Eastern Mediterranean Sea, Tunisia) by using flow cytometry. Continental Shelf Research, 2015, 93, pp.27-38. ⟨10.1016/j.csr.2014.10.002⟩. ⟨hal-01436533⟩
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