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

Authors :
Michel Denis
A. Hamza
I. Hamdi
Chantal Bézac
M. Bel Hassen
Sami Maalej
Amel Bellaaj-Zouari
Aude Barani
H. Khemakhem
Institut méditerranéen d'océanologie (MIO)
Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN)
Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS)
Source :
Continental Shelf Research, Continental Shelf Research, Elsevier, 2015, 93, pp.27-38. ⟨10.1016/j.csr.2014.10.002⟩, Continental Shelf Research, 2015, 93, pp.27-38. ⟨10.1016/j.csr.2014.10.002⟩
Publication Year :
2015
Publisher :
HAL CCSD, 2015.

Abstract

TheGulfofGabesintheEasternMediterraneanBasinisoneofthelargestcontinentalshelvesandisahighly productivearea.ThisisincontrasttotheEasternMediterraneanBasinasawholewhichisoligotrophicto ultraoligotrophic.Overrecentyears,duetoincreasedpressurefromanthropologicalactivities,therehas beenadeclineinthebiologicalresourcesintheGulfofGabes.Thishasledscientiststofocustheirresearch on thedifferenttrophiclevelsofthefoodchainandinparticularonphytoplankton.Studiesdedicatedto phytoplanktonintheGulfofGabeshavepreviouslyreliedonconventionalglobalapproaches.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.

Details

Language :
English
ISSN :
02784343 and 18736955
Database :
OpenAIRE
Journal :
Continental Shelf Research, Continental Shelf Research, Elsevier, 2015, 93, pp.27-38. ⟨10.1016/j.csr.2014.10.002⟩, Continental Shelf Research, 2015, 93, pp.27-38. ⟨10.1016/j.csr.2014.10.002⟩
Accession number :
edsair.doi.dedup.....c10e6fc9363e7e817c56c24e1178515c
Full Text :
https://doi.org/10.1016/j.csr.2014.10.002⟩