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

Abstract : 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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Article dans une revue
Continental Shelf Research, Elsevier, 2015, 93, pp.27-38. 〈10.1016/j.csr.2014.10.002〉
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Soumis le : lundi 16 janvier 2017 - 15:03:45
Dernière modification le : vendredi 22 juin 2018 - 13:44:11

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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, Elsevier, 2015, 93, pp.27-38. 〈10.1016/j.csr.2014.10.002〉. 〈hal-01436533〉

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