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The influence of hydrodynamic processes on

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The influence of hydrodynamic processes on zooplankton transport and distributions in the North Western Mediterranean: estimates from a Lagrangian model Z.F.Qiu a,b, A.M.Doglioli a, Z.Y.Hu a, P.Marsaleix c, F.Carlotti a,? aLaboratoire d'Oceanographie Physique et Biogeochimie, Aix Marseille Universite, CNRS, UMR 6535, Marseille, France bKey Laboratory of Ocean Circulation and Waves, Institute of Oceanology, CAS, Qingdao, China cLaboratoire d'Aerologie, 14 Avenue Edouard Belin, Toulouse, France Abstract A Lagrangian module has been developed and coupled with the 3D circulation model Symphonie to study the influence of hydrodynamic processes on zooplankton trans- port and distributions in the North Western Mediterranean (NWM). Individuals are released every 3 days from March to August 2001 in two initial areas: around the DYFAMED sampling station in the central Ligurian Sea and in the Rhone river plume. Then the individuals are tracked for 40 days either as passive particles or with a simple diel vertical migration (DVM) pattern. The simulations suggest strong seasonal patterns in the distributions of the individuals released around the DY- FAMED sampling station. Individuals spread all over the NWM basin after 40 days Preprint submitted to Elsevier 23 May 2010

  • necessarily passive

  • hydrodynamic processes

  • offshore circulation

  • lagrangian model

  • transport and69

  • enables zooplankton

  • shelf transport


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TheinfluenceofhydrodynamicprocessesonzooplanktontransportanddistributionsintheNorthWesternMediterranean:estimatesfromaLagrangianmodelZ.F.Qiua,b,A.M.Dogliolia,Z.Y.Hua,P.Marsaleixc,F.Carlottia,aLaboratoired’Oce´anographiePhysiqueetBioge´ochimie,AixMarseilleUniversite´,CNRS,UMR6535,Marseille,FrancebKeyLaboratoryofOceanCirculationandWaves,InstituteofOceanology,CAS,Qingdao,ChinacLaboratoired’Ae´rologie,14AvenueEdouardBelin,Toulouse,FranceAbstractALagrangianmodulehasbeendevelopedandcoupledwiththe3DcirculationmodelSymphonietostudytheinfluenceofhydrodynamicprocessesonzooplanktontrans-portanddistributionsintheNorthWesternMediterranean(NWM).Individualsarereleasedevery3daysfromMarchtoAugust2001intwoinitialareas:aroundtheDYFAMEDsamplingstationinthecentralLigurianSeaandintheRhoˆneriverplume.Thentheindividualsaretrackedfor40dayseitheraspassiveparticlesorwithasimpledielverticalmigration(DVM)pattern.ThesimulationssuggeststrongseasonalpatternsinthedistributionsoftheindividualsreleasedaroundtheDY-FAMEDsamplingstation.IndividualsspreadallovertheNWMbasinafter40daysPreprintsubmittedtoElsevier23May2010
butdifferentpatternsoccurdependingontheseason,theinitialdepthsofreleaseandthecapacityofDVM.Offshore-shelftransportonlyoccursinAprilandMaywithparticlesendingupintheGulfofLions(GoL)inlowconcentrations.Inothermonths,theNorthernCurrent(NC)canbeconsideredasabarrierforparticlesenteringtheGoLfromtheoffshoresea.AquartertoahalfofpassiveindividualsreleasedintheRhoˆneriverplumeremainintheGoL.TherestistransportedbytheNCtowardstheCatalanSea.ApplyingasimpleDVMschemedoesnotincreasetheretentionofparticlesontheshelf.Keywords:Lagrangian,zooplankton,NorthWesternMediterranean,GulfofsnoiL11Introduction2Overthepastfewdecades,ithasbecomeclearthatphysicalprocesses3areimportantdriversofpopulationdynamicsintheoceans(Milleretal.,41998;Batchelderetal.,2002).Zooplanktonorganismsarecriticallydependent5ontheirphysicalenvironmentsbuttheyarenotnecessarilypassiveparticles6(Batchelderetal.,2002;Cianellietal.,2007;SentchevandKorotenko,2007;7Carretal.,2008).Theyswimverticallywhichinfluencestheirspatio-temporal8distributions.Ateachphaseoftheirdevelopment,theyhavetofindprey9andavoidpredators.Attheadultstagetheywillseekmatesandreproduce.10Therefore,zooplanktontransportinavarietyofphysicalconditionscanbe11consideredasthecombinationoftwocloselylinkedprocesses.Thefirstis12zooplanktontransportbynon-stationaryflowfieldsandthesecondistheCorrespondingauthor.Emailaddress:francois.carlotti@univmed.fr(F.Carlotti).2
13behaviouralresponseofzooplankton,mainlybyswimming,tothechangesof14environmentalconditions.15Wheninvestigatingtherelationshipsbetweenparticledistributionandphys-16icalprocesses,researchersoftenusedbio-physicalmodels(e.g.Levyetal.,172000;Oschlies,2002).Lagrangianparticletrackingmodelscoupledwithhy-18drodynamicmodelsareparticularlyefficienttoolstoexaminetheroleplayed19byvariousphysicalprocesses,tostudytransportprocessesoveranentirebasin20andtosimulatecomplexandinteractiveprocessesactingatdifferentscales21(e.g.Milleretal.,1998;Blankeetal.,1999;Falcoetal.,2000;Guizienetal.,222006;Speirsetal.,2006;Lettetal.,2007).23RecentdevelopmentsofLagrangianmodelinghavehighlightedthelinks24betweenphysicalstructures,zooplanktonbehaviourandmarineproductivity25inregionssuchastheBenguelaecosystem(Mullonetal.,2003;Lettetal.,262007)ortheGeorgesBank(Milleretal.,1998).Cianellietal.(2007)simulated27theparticleexchangeintheGulfofLions(GoL)usingaLagrangianapproach28coupledwithathree-dimensional(3D)circulationmodel.Theyfoundthat29particledistributionsarestronglyrelatedtothemesoscaleandsub-mesoscale30hydrodynamicstructuresontheshelfandtotheoffshorecirculationassociated31withtheNorthernCurrent(NC).32Dielverticalmigration(DVM)isthemostcommonzooplanktonswimming33behaviourinwhichorganismsresideinsurfaceornear-surfacewatersatnight34andindeeperwatersduringtheday.Thisbehaviourenableszooplanktonto35feedinrelativelyproductivesurfacewatersatnightandavoidvisualpredators36duringtheday(Haney,1988).ThepotentialeffectofDVMonzooplankton37transporthasbeendemonstratedbyseveralresearchers(Batchelderetal.,3