Live benthic foraminiferal faunas from the French Mediterranean Coast: towards a new biotic index of environmental quality

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Ecological Indicators

j o ur na l h o me p a g e :w w w . e l s e v i e r . c o m / l o c a t e / e c o l i n d

Live benthic foraminiferal faunas from the French Mediterranean Coast: Towards a new biotic index of environmental quality

Christine Barras

, Frans J. Jorissen

, Céline Labrune

, Bruno Andral

, Pierre Boissery

aUMRCNRS6112LPG-BIAF,Bio-IndicateursActuelsetFossiles,AngersUniversity,2BoulevardLavoisier,49045AngersCedex,France

bUPMC,UniversitéParis06,ObservatoireOcéanologique,66650Banyuls/Mer,France

cUMRCNRS8222LECOB,ObservatoireOcéanologique,66650Banyuls/Mer,France

dIFREMER,LaboratoireEnvironnementRessourcesProvence-Azur-Corse,CentreMéditerranée–ZonePortuairedeBrégaillon–BP330,83507La Seyne-sur-MerCedex,France

eAgencedel’EauRhône-MéditerranéeetCorse,2-4alléedeLodz,69363LyonCedex07,France

a r t i c l e i n f o

Articlehistory:

Received10April2013 Receivedinrevisedform 17September2013 Accepted21September2013

Keywords:

CoastalMediterraneanSea Foraminiferalfaunas Indicativespecies Tolerantspecies Bioticindex

WaterFrameworkDirective

a b s t r a c t

Inthisstudy,living(RoseBengalstained)foraminiferalfaunasfrom31stationsalongtheentireFrench MediterraneanSeacoastexceptCorsicahavebeenanalysed.InthecontextoftheWaterFramework Directive,theaimwastodevelopabioticindextoevaluatethebenthicecosystemquality.Therefore, differentfaunalparameters(diversityindices,wallstructureproportion,andindicativespeciesgroups) havebeentestedtodeterminetheirrelevanceasindicatorsofenvironmentalconditions.Thebestresults areobtainedwithabioticindexbasedontherelativeproportionofstress-toleranttaxa.Forecosys- temqualityevaluation,itisessentialtodistinguishbetweennaturalandanthropogeniceutrophication phenomena.Inordertodoso,weappliedacorrectiononourbioticindex,usingtheexpectedpercent- ageofstress-tolerantspeciesinnaturalenvironments,infunctionofsedimentgrainsize(percentage

<63␮m).Finally,acomparisonofthedifferentfaunalparameterscalculatedfortwodifferentsediment intervals(0–1and0–4cm)indicatesclearlythattheanalysisoftheuppermostcentimetreofthesediment issufficienttoobtainrelevantinformationneededforbio-monitoringpurposes.

© 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Duetotheirstrategiclocationattheinterfaceofmarineandter- restrialareas,coastalecosystemshavebeenimpactedbyhuman activities since the advent of human societies. Anthropogenic impactincoastalmarineecosystemshasmultipleorigins,suchas urbansewage,industrialandagriculturalactivitiesorfisheries,and resultsinenvironmentalproblems,suchaseutrophication,oxygen deficiency,chemicalpollutionorphysicaldisturbance.Awareness ofrecent changes inecologicalconditions in manycoastalseas hasfosteredaneedtoassessincreasinganthropogenicpressures andtheirconsequencesonsedimentandwaterquality,andtosug- gestmeasurestoreversethistrend.Inthiscontext,theEuropean commissionimplementedtheWaterFrameworkDirective(WFD, Directive2008/56/EC)withtheaimtoobtain(ortomaintain)a

“goodstatus”foralltheEuropeanwatersby2015.TheWFDdefines theecologicalstatusasthequalityofthestructureandfunctioning ofecosystemsandisassessedusingdifferentplanktonicandben- thicindicators(e.g.phytoplankton,macro-algae,angiosperms,fish

∗Correspondingauthor.Tel.:+33241735002.

E-mailaddress:christine.barras@univ-angers.fr(C.Barras).

faunasandsoftsubstratebenthicinvertebratefauna)(Devlinetal., 2007).

Thestudyofthebenthicmacrofaunaisthetraditionaltoolfor benthicecologicalqualityassessmentandbio-monitoringstudies, sincemacrofaunarespondsinapredictablewaytoanthropogenic and naturalstress(Pearsonand Rosenberg,1978).Environmen- talmanagersneedaneasilyinterpretableecologicalqualitystatus based onquantitativedata. Numerousbiotic indicatormethods weredevelopedformacrofauna(seereviewinDiazetal.,2004) basedeitherondiversityindices(e.g.Shannonindex,Pielou,1975) oronindicesbasedontherelativeproportionsoffaunalgroupswith differentecologicalcharacteristics.Someofthelattermethodsare basedongroupswithdifferentfeedingstrategies(e.g.ITI,Word, 1979), whereas others distinguish several classes of pollution- sensitive versus opportunistic, pollution-tolerant, species (e.g.

AMBI, Borjaet al., 2000; BENTIX,Simbouraand Zenetos, 2002;

BOPA,GomezGesteiraandDauvin,2000;DauvinandRuellet,2007;

BQI,Rosenbergetal.,2004).

Morerecently,benthicforaminiferalfaunashavebeenincreas- inglyusedasbio-indicatorsofanthropogenicpollution.Initially, foraminiferaweremainlystudiedinfossilrecordsfor biostrati- graphic and paleoenvironmental purposes. The interest for the living organisms greatly expanded when researchersstarted to 1470-160X/$–seefrontmatter© 2013 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.ecolind.2013.09.028

studytheirecologyin1960s.Becauseoftheirshortlifecycle(3 monthsto2 years, Murray, 1991),theseorganisms are ableto respondrapidlytoenvironmentalchanges,withachangeindiver- sityand in species composition.Such rapidadaptive responses havebeenobservedinresponsetochangesin thequantityand qualityoforganicsupplies (e.g.AltenbachandSarnthein,1989;

Corlissand Emerson,1990; Corliss,1991; Hergueraand Berger, 1991;RathburnandCorliss,1994;Jorissenetal.,1995,1998;De Rijketal.,2000;Licarietal.,2003),inoxygenconditions(e.g.Sen GuptaandMachain-Castillo,1993;Gooday,1994;Jorissenetal., 1995;Goodayetal.,2000),pH(e.g.Murray, 1989),salinity and temperature(e.g.Murray,2006).Moreover,foraminiferaareubiq- uitousinmarineenvironments,inhabitingtransitionaltoabyssal areas and tropical to polarlatitudes (review in Murray, 2006).

Foraminiferaare abundantin marine sediments,even in deep- seaenvironments where theycommonly represent more than 50%ofthetotalbiomass(Goodayetal.,1992).Thehighnumber ofindividualssampledwithalittlequantityofsedimentassures therobustnessof dataanalysis and limitstheimpactof samp- lingontheseafloor.Furthermore,foraminiferaltaxonomyiseasy comparedtotheidentificationofmacrofauna,sinceonlyasingle biologicalgroupisconsidered,insteadofseveralphyla.Although foraminiferarepresentonlyapartofthetrophicnichesandguilds, theecologicalcharacteristicsofthedifferentspeciesaredifferent enoughtoobtainreliable informationabouttheenvironmental conditions,as ithasbeen shown ina wide range of paperson benthicforaminiferalecology (e.g.Goodayand Rathburn,1999;

Jorissenetal.,2007;Murray,2006).Finally,themainadvantage offoraminiferaistheconservationof alargepartoftheirtests (shells)inthesedimentaftertheirdeath.Thestudyofdeadfaunas atdifferentdepthsinthesedimentcangiveimportantinformation aboutthenaturalconditionswhichexistedbeforeasitebecame polluted.Thisisespeciallyusefulincaseoftheabsenceofanenvi- ronmentalbaselinestudy(Alve,1995).Comparisonoflivingfaunas andpre-impactfaunascanalsoyieldessentialinformationabout individualspeciesecologicalstrategies.Forexample,opportunistic specieswhichhavecolonisedthearea,orsensitivespecieswhich disappearfromtheareaafter theonset ofpollution, caneasily berecognised. Assuch, thecomparisonofliveand deadfaunas canensurethatlistswithspecies ecologicalcharacteristicscor- rectlytranslatethebehaviourofthevariousspeciesatthestudy site.

Alltheseadvantagesmakeforaminiferaaninnovativeandvery interestingtoolforbio-monitoringstudiesofanthropogenicimpact (reviewsinAlve,1995;Nigametal.,2006;FrontaliniandCoccioni, 2011).Thefirststudiesusingforaminiferaasindicatorsofenvi- ronmentalqualityappearedin1960s(Resig,1960;Watkins,1961;

Bandyetal.,1964,1965;Seiglie,1968,1971;Clark,1971).Today, numerousstudiesuseforaminiferaasbio-indicatorsofdifferent typesofpollutionsuchaseutrophication(e.g.Platonetal.,2005;

Mojtahidetal.,2008;Hyams-Kaphzanetal.,2009),heavymetals (e.g.Alve,1991;ArmynotduChateletetal.,2004;Frontaliniand Coccioni,2008;Bergaminetal.,2009;Cherchietal.,2009;Coccioni etal.,2009;Frontalinietal.,2009;Romanoetal.,2009;Vilelaetal., 2011),urbansewage(e.g.Buroneetal.,2006;Teodoroetal.,2010), oildrillingactivities(e.g.Durrieuetal.,2006;Mojtahidetal.,2006;

Ducheminetal.,2008;Jorissenetal.,2009;Denoyelleetal.,2010), oilspills(e.g. Morvanet al.,2004)oraquaculture(e.g.Bouchet etal.,2007).However,nostandardisedprotocolsforsamplingand samplingtreatmenthavebeendefineduntilrecently(Schönfeld etal.,2012)sothatdirect comparison ofthevarious studiesis verydifficult, ifnot impossible.However, a careful observation ofthefaunalpatternsdescribedinthesestudiesallowsidentify- ingdifferenttypesofspeciesbehaviourinresponsetopollution.

Justasformacrofauna,somestudiestriedtodevelopbioticindices, eitherbasedonfaunaldiversity(e.g.Bouchetetal.,2012)oronthe

proportionofindicativespecies(e.g.Mojtahidetal.,2006;Jorissen etal.,2009).

Inthepresentstudy,weanalyseliving(RoseBengalstained) foraminiferal faunas from the French Mediterranean Sea coast (exceptCorsica)inthecontextoftheWFD,withtheaimtoeval- uatetheecosystemquality.Thestudyarearepresentsmorethan 1000kmofcoastalzoneforwhichthepresenceofanthropogenic stressparametersisbadlyknown.Therearenopointsourcesof pollutionclosetosamplingstations,andtherearenowell-defined reference stations exempt of anyanthropogenic impact either.

Therefore,wefirstanalysedthevariousfaunalparameters(faunal density,diversityandfaunalcomposition)thatcouldbeusedforthe evaluationoftheenvironmentalquality.Next,wetriedtotakeinto accountthenaturalvariabilityofthesysteminordertodistinguish betweentheimpactofthisnaturalvariabilityandaputativeanthro- pogenicimpact.Unfortunately,ourstudywasperformedpriorto theestablishmentofastandardisedsamplingandsamplingtreat- mentprotocolbytheFOBIMOgroup(Schönfeldetal.,2012),and thereforedoesnotfollowallrecommendationsmadeinthispaper.

However,bycomparingthefaunaldataforthe0–1cmand0–4cm sedimentlevels,wetestedthepossibilitytorestrictfaunalanaly- sestothetopmostcentimetre,asrecommendedbySchönfeldetal.

(2012).Bystudyingonlythetopmostcentimetre,thetimeneeded forpickingtheforaminiferawouldbelargelyreduced,makingthe methodbetteradaptedforcost-efficientbio-monitoringstudies.

Thisstudyrepresentsthefirstcrucialstepforthedevelopmentof anewbioticindexbasedonbenthicforaminiferalfaunas.Inorder tobeusedroutinelyinfuturesurveys,thepresentedindexwill needtobetestedincaseswithastrongpollutiongradientandin othergeographicareas.Sinceitisthefirstlargescalestudyofliving foraminiferalfaunasalongtheentireFrenchMediterraneancoast (exceptCorsica),theresultsofthepresentstudycanalsoserveas aglobalinventoryandabaselineforfuturestudies.

2. Materialsandmethods

2.1. Regionalsettingofthestudyarea

The Mediterranean Sea is generally considered as a semi- enclosedoligotrophicbasin.Lowsalinitysurfacewaterfromthe AtlanticOcean enterstheMediterranean Seathrough theStrait ofGibraltarandcreatestheLiguro-ProvencalCurrent(LPC)which flowsalongtheFrenchMediterraneancoast,fromItaly toSpain throughtheGulfofLion(MillotandTaupier-Letage,2005;Pairaud andDesmare,2011).TheLPCcandevelopsmallscalegyres,depend- ingofthebackgroundstratificationor externalforcingthat can influencetheshelfcirculation.

Thereisacleardifferenceinthecontinentalshelfcharacteris- ticsalongtheMediterraneanFrenchcoast.Thecontinentalshelf infrontoftheProvenceAlpeCôted’Azurregionisrelativelynar- row,lessthan1milewide(PairaudandDesmare,2011).Eastof Toulon,anareawithrockyseafloorisinterruptedbyseveralsmall embaymentscontainingmorefine-grainedsediments,suchasthe BayofVillefranche,betweenVillefrancheandNice.Onthewestern sideoftheFrenchMediterraneancoast,thecontinentalshelfofthe GulfofLioniswide(upto40miles;Bassettietal.,2006)andcon- sistsofalargecrescentshapedareaincisedbysub-marinecanyons (BernéandGorini,2005).Thebottomsedimentdistributiondis- playsamid-shelfmudbeltandtheinnerandoutershelfregions withmixedsandytomuddydeposits(Aloisietal.,1973).

TheGulfofLionsisalsostronglyinfluencedbytheRhôneRiver input (Raimbault and Durrieu de Madron, 2003).Witha mean annualdischargeof1700m³/s(Thilletal.,2001),theRhôneisoneof themainsourcesoffreshwaterandorganiccarbonfortheMediter- raneanSea(Pont,1997;Sempéréetal.,2000).TheRhôneRiverhas

ameansedimentdischargeofabout9.9±6.4×10⁹kg/yr(Sempéré etal.,2000;Pontetal.,2002),accountingfor80%oftheriverine inputtotheGulfofLions(DurrieudeMadronetal.,2000).The Rhôneprodeltaischaracterisedbysiltymudswithhighorganiccar- boncontent(1–2%;DurrieudeMadronetal.,2000)andveryhigh sedimentaccumulationrates.Alsosmallercoastalrivers(e.g.the TêtandHéraultRivers)cansignificantlycontributetothesediment budgetinthisarea(Kimetal.,2006).

Finally,thispartoftheMediterraneanSeaischaracterisedby endemicPosidoniaseagrassmeadows.Inourstudyarea,Posidonia meadowsarelocatedinfrontofBanyuls-sur-Mer(Blanc-Vernet, 1969,1984;Vénec-PeyréandLeCalvez,1981,1988;Vénec-Peyré, 1984)andformacontinuousbandfromtheeastsideoftheRhône prodeltatotheItalianfrontier(Boudouresqueetal.,2006).

2.2. Samplingstrategy

FromMarch26thtoApril9th2009,31stationsweresampledfor thestudyofbenthicforaminiferalfaunasalongtheFrenchMediter- ranean coaston board of the research vessel“Europe” (Fig. 1, AppendixA).Thelocationofthestationswaschosenaccordingto theWFDcriteria,i.e.withinonemilefromthecoastlineandatleast onestationperwaterbody(i.e.acoherentgeographicareabasedon physical(e.g.hydrodynamic,sedimentological)criteriainfluencing biologicalactivities).

2.3. Foraminiferalsamplingmethods

SurfacesedimentwassampledusingaReineckboxcorer,which was subsampled with plexiglass cores (diameter 7.1cm). Only stationCerbèrecouldbesampledwithaninterfacecorer(Gemax twincorer,corediameter8.8cm).

Onboard,coreswereslicedhorizontally,everyhalfcentime- trefromthesurfaceto2cm depth,everycentimetrebetween2 and6cmdepth,andeverytwocentimetresfrom6to10cmdepth.

Sometimes,coresweretooshorttosampleuntil10cmdepth.For stationsGruissan,LavandouandFaraman,itwasnotpossibleto

takeacoreintheReineckbox(e.g.becauseofthepresenceofmany pebbles),andthefirstcentimetreofthesurfacewassampledwith aspoon.Inthiscase,afterhomogenisation,50cm³ofsedimentwas subsampledforforaminiferalanalyses.

Aftersampling,sedimentswerestoredinplasticbottlesfilled withamixtureofethanol(95%)andRoseBengalstain(1g/l).Rose Bengaliscommonlyusedtoobtainarapidoverviewoftheliving faunas.Itstainsthecytoplasmofforaminiferaaliveatthetimeof sampling(Walton,1952),orwhichdiedinarecentpast(weeks tomonths,Bernhard, 1988;Corliss and Emerson,1990),and in whichthenon-degradedproteinsarestillstainable.Ethanolallows preservingstainedcellulartissuesforaprolongedperiodoftime.

Samplesweregentlyshakentoobtainahomogeneousmixtureand weretransportedtothelaboratoryforfurtherprocessing.

2.4. Foraminiferalanalyses

Inthelaboratory,sedimentsamplestreatedwithRoseBengal weresievedthrough150and,ifnecessary,500␮mmeshscreens.

For our study, only the >150␮m or 150–500␮mfraction was analysed, depending onthe station. The >500␮msize fraction was removedwhen the sediment containedlarge quantitiesof vegetal detritus, shellfragments or coarsesand,which compli- cated foraminiferal picking. The>500␮mfraction waschecked on someoccasions and no living foraminiferawere found.We consider therefore that in our study area, the resultsobtained for the 150–500␮m size fraction are comparable with those of the >150␮m fraction. Also Bouchet et al. (2012) observed that the number ofindividuals >500␮m in theirsamplesfrom theNorwegianSkagerrakcoastwasminimal.Unfortunately,our foraminiferalanalyseswereperformedpriortotheestablishment of the methodological recommendations of the FOBIMO group (Schönfeldetal.,2012).Themaindifferencesbetweenourmethod- ology and theone described by the FOBIMO group is the use of the >150␮m instead of the >125␮m size fraction, and the absenceofreplicatecores,whichcouldnotbesampledduetotime constraints.

Fig.1. LocalisationofthesamplingstationsalongtheFrenchMediterraneancoast.

Rose Bengal stained foraminifera were wet-picked in 50%

ethanolunderabinocularmicroscope(LeicaMZ95).Onlyspeci- mensshowingaclearpinkcolour(orred,dependingonthespecies) inallbut thelast chamberswere consideredasliving fauna.If necessary,opaqueporcelaneousandagglutinatedspecimenswere brokentocheckforthepresenceofprotoplasm.Next,foraminifera werearrangedonmicropaleontologicalslides,identifiedonspecies levelusingtaxonomichandbooks,andcounted.

Inordertostudytheverticaldistribution(andmicrohabitats) oflivingforaminiferainthesediment,14stationshavebeenana- lyseduntilatleast4cmdepthinsediment(stationToulonGrande Radehasonlybeensampleduntil3cm)andamaximumof10cm depth.Thefaunalparametersfromthe0–4cmsedimentinterval havebeencompared tothose obtainedforthe0–1cm interval, to determine whether the study of deeper sediment intervals (time-consumingandthereforemoreexpensive)yieldsimportant complementaryinformation.Animportantaimofthepresentstudy wastodeterminewhetherthestudyofthe0–1cmsedimentinter- valissufficienttodescribethequalityofthebenthicecosystem,if so,supportingoneoftherecommendationsoftheFOBIMOgroup (Schönfeldetal.,2012).

2.5. Foraminiferalparameters

Foreachstationandstudiedsedimentinterval(i.e.0–1cmor 0–4cm),wecalculatedthefollowingfaunalparameters:(1)total foraminiferaldensity(standardisedfora50cm²sedimentsurface), (2)specificrichness,and(3)therespectiveproportionofthethree principalforaminiferalgroups(perforate,porcelaneousandagglu- tinatedforaminifera).Todescribethediversityoftheforaminiferal faunas,weusedtheShannon–WienerHindex(HayekandBuzas, 1997)andtheequitabilityJindex(Pielou,1966)whicharedefined bythefollowingequations:

H=− n_i N

×ln

i

N

and J= H ln(S)

wheren_iisthenumberofindividualsofspeciesi,Nisthetotal number of individuals, and S is the totalnumber of species at theconsideredstation.TheShannon–Wienerindexlinksthenum- berofspeciestotheassemblagedensitywhereastheequitability indexfocusesparticularlyonthedistributionofindividualdensities betweenthedifferentspecies(itdistinguishesbetweensamples withcomparabledensitiesforallspeciesorsampleswithadomi- nanceofoneorafewspecies).

Becauseforaminiferalabundancesareverydifferentbetween stations,wealsocalculated (usingPASTsoftware,Hammer and Harper,2005)theexpectednumberofspeciesfromasub-sample of50individualstakenfromthepopulationofalltheindividuals (ES50).Theconceptofexpectednumberofspecies(ES)wasfirst introducedbySanders(1968)butitscomputationwasmodifiedby Hurlbert(1971).Itiscomputedas:

ES₅₀=1−

i=1

(N−Ni)!(N−50)!

(N−Ni−50)!N!

whereNisthetotalabundanceofindividualsattheconsidered station,N_iistheabundanceoftheithspeciesattheconsidered station,andsisthenumberofspeciesattheconsideredstation.

ES50wasnotcalculatedwhenabsolutedensitywaslowerthan50 individuals.

Aftertestingthedatafornormaldistribution(Shapiro–Wilktest adaptedtosmallsizesamples,n<50),weusedparametric(Stu- denttest)ornon-parametric(Wilcoxontest)statisticalanalysesfor pairedsamplesinordertocomparethedataobtainedfor0–1cm and0–4cmsedimentintervals.Differenceswereconsideredsignif- icantwhenp<0.05.

Wealsostudiedtheverticaldistributionofthevarioustaxain thefirstcentimetresofsediment.Foraminiferalmicrohabitatsare controlledbyphysical,chemicalandbiologicalprocesses(Corliss, 1985;Buzasetal.,1993;Jorissenetal.,1995).Themicrohabitatcon- ceptallowsabetterunderstandingofthefoodandoxygenneeds ofeachspecies.ThereforewecalculatedtheAverageLivingDepth (ALDx)forthetotalfaunaofthecoreasfollows(Jorissenet al., 1995):

ALD_x=

i=1,x

(n_i×D_i) N

inwhichALDxistheaveragelivingdepth(incm)ofthefaunaina coreofxcentimetresdepth;n_iisthenumberofspecimensinthe sedimentintervali;D_iisthemidpointofthesedimentintervali(in cm);andNisthetotalnumberofindividualsforalllevels.

2.6. Environmentalparameters

Pore water oxygen profiles were measured onboard under insitutemperatureconditionsusingacathode-typemini-electrode (100 or 500␮m tips, Unisense©) (Revsbech, 1983; Helderand Bakker, 1985;Revsbechand Jørgensen, 1986)forReineck cores withawell-preservedsedimentwaterinterfacewithoverlyingbot- tomwaters.Theseanalysesweregenerallyduplicatedandallowed todeterminethemaximumoxygenpenetrationdepth(OPD)inthe sediment.

During the oceanographic cruise, in addition to sediment for foraminiferal analysis,sediment wasalsosampledfor grain size and total organicmatter analyses.Grain sizeanalysis was conductedusingaMalvern®Mastersizer2000lasermicrogranu- lometer.Organicmattercontentcorrespondstoashfreedryweight.

Weight-lossaftercombustion(450^◦C,5H)oflyophilisedsamples ismeasured.

3. Results

3.1. Sedimentcharacteristics

Thelargedifferenceinthecontinentalshelffeaturesbetween the eastern and western French Mediterranean coast has an importantimpactonthesedimentcharacteristicsobservedatour samplingstations.

The31 stations sampledhave beenchosen accordingtothe WaterFrameworkDirectivestrategy,andaresystematicallypos- itionedwithin1milefromthecoastline.Becauseofthissampling policyandtheheterogeneityoftheFrenchMediterraneancoast, thereisacleardifferenceintheaveragewaterdepthofthestations fromthewesternpartofourstudyarea(18monaverage)com- paredtothosefromtheeast(40monaverage).Thelimitbetween thetwoareasisapproximatelypositionedbetweenthestationsFos andCarry(Fig.2a,AppendixB).

Thegrainsizeanalysesshowacleardifferencebetweenwest- ernandeasternstations(Fig.2c–e,AppendixB).Stationswestof Carrycontainalowproportionofsand>250␮m,withtheexcep- tionof thestationsCollioureand Cerbère, whichare locatedat themostwesternpartoftheFrenchcoast.Conversely,theeast- ern stations show a highproportion of medium (250–500␮m) and coarse (500–1000␮m) sands, with the exception of some stations(e.g.MarseilleJetée,IleEmbiez,Nice,Menton).Thereis a significantpositivecorrelationbetweenthepercentageofthe

>500␮mfractionandwaterdepth(r=0.50,p<0.05;AppendixC), whichunderlinesthedifferenceinsedimentcharacteristicsalong theFrenchMediterraneancoast.Conversely,stationslocatedclose tothe Rhône rivermouth (Fos, Carteau, Beauduc) showa high

Fig.2. Environmentalparametersforthe31samplingstations,fromwest(leftside)toeast(rightside)stations:(a)waterdepth,(b)percentageoforganicmatter,(c) percentageofclayandsilt(<63␮m),(d)percentageofveryfinetofinesand(63–250␮m),and(e)percentageofmediumtocoarsesand(>250␮m).

proportion ofclay and siltparticles (<63␮m), in response toa continuousinputoffine-grainedsedimentfromtheRhôneriver.

The organic matter content (Fig. 2b, Appendix B) has been analysedonthetotalsediment,withoutanypre-treatment.Con- sequently,this organicmatter is notonly composed ofmarine phytoplanktondetritusandofriver-suppliedcontinentalorganic matter,butalsobymuchlargerdebrisofmacro-algaeandseagrass (roots,leaves).Thefeedingstrategiesofforaminiferaarevarious, fromdetritivoryonlabile or alsomore refractory organicmat- ter,tocarnivoryandbactivory(reviewinMurray,2006).In our studyarea, marineand continentalsedimentary organicmatter canprobablyserveasfoodforthebenthicforaminifera,whichis probablynotthecasefortheseagrassdebris.Infact,thetrophic stateofmarinesedimentsisnotonlydependentontheabsolute

quantitiesoforganicmatterdepositedontheseafloor,butitisalso afunctionofitsbiochemicalcompositionandnutritionalquality forconsumers(Puscedduetal.,2009).Severalstudies(e.g.Mateo et al.,2006;Østergaard Pedersenet al.,2011)haveshown that theroots,rhizomes,andleafsheathsofPosidoniadecomposevery slowlyduetotheirhighcontentoflignin,cellulose,andphenolic compounds(Harrison,1989;Klapetal.,2000),whicharenotreadily degradedbymicrobes(GodshalkandWetzel,1978).Thereforethe largeamountsofPosidonialeavesandrootsfoundatseveralsta- tionsinourstudyarea,resultinginveryhighOMvaluesinsome stations,cannotbeconsideredasreadilyavailablefoodforben- thicorganisms.Consequently,itappearsimpossibletousetheOM percentagesasmeasureofthetrophiclevelorasanindicatorof anthropogenicpressure.Thereisnoclearwest-easttrendinthe

OMpercentage(Fig.2b),butthereisastatisticallysignificantpos- itivecorrelationbetweentheOMcontentandthepercentageof clay/silt(<63␮m)particles(r=0.42,p<0.05;AppendixC),aswas observedpreviouslyinothercoastalareas(e.g.Jorissen,1987,1988;

Fontanieretal.,2008).Largequantitiesofmacro-algaeand sea- grasses(e.g.detritusofPosidoniaroots)observedinthesediment collectedatstationseastofFosexplaintheabnormallyhighOM percentagesfoundinsomestationswithcoarsesediments(e.g.Ile Maire,Porquerolles,IleLevant).

Summarising,naturalenvironmentalcharacteristicsappearto beverydifferentbetweenthewesternstations(lowerwaterdepth, finesediment,enriched insedimentaryorganicmatter)andthe easternstations(higherwaterdepth,coarsersediment,andsome- times abundant plant remains) in our study area. The faunal assemblagesthatarecolonisingthesedifferenttypesofenviron- mentswillthereforebeverydifferentnaturally.Thisbiaswillhave tobetakenintoaccountwhentryingtoconstructabio-indicator method based onthe foraminiferal faunas.However, it is very

Fig.3.Densityanddiversity(speciesnumber)oflivingforaminiferalfaunasforthe31samplingstations,fromwest(leftside)toeast(rightside),consideringeither0–1cm (black/diamonds)or0–4cm(white/squares)sedimentintervals:(a)livingforaminiferaldensity(numberofspecimensstandardisedfor50cm²,crossesnotifysamplesfor whichonlythefirstcmofsedimentwasanalysed),(b)speciesrichness,(c)Shannon–Wienerindex,(d)equitabilityindex,and(e)ES50.NB:ForstationToulonGrandeRade dataarebasedonastudyofthe0–1and0–3cmintervals.

probablethatthisstrongwest-eastdichotomywillequallyaffect themacrofaunaldistribution.

3.2. Diversityanddensityofthelivingfauna

Livingforaminiferaldensitiesstandardisedfor50cm²arehighly variable among stations (Fig. 3a, Appendix B). For the 0–1cm sediment interval (31stations considered),thetotalnumber of foraminiferavariesbetween22specimens/50cm²forstationFara- manand2091specimens/50cm²forstationGrauduRoi.Forthe 0–4cmsedimentinterval(14stationsconsidered),totaldensities varybetween387and2526specimens/50cm²forstationsIleMaire and Graudu Roi, respectively. Thevery low densities foundat stationsFaraman,LavandouandPorquerolles(22,43and51spec- imens/50cm²,respectively)couldresultfromthelossofalarge partofthesuperficialsedimentbeforetheReineckcorereached thedeckoftheship.

ThestationsLeucate,VillefrancheandMentonexhibitaparticu- larlystrongdifferenceindensitiesbetweenbothstudiedsediment intervals(0–1and0–4cm),indicatingthepresenceofabundant liveforaminiferalfaunasindeepersedimentlayers.Inmostother stations,thisdifferenceissmaller.

Diversity indices are relatively high at all studied stations (Appendix B). Species richness in the first centimetre of sedi- mentvariesbetween20(stationAgdeEst)and73species(station Monaco) (Fig. 3b). The Shannon–Wiener index (Fig. 3c) varies between1.9(stationGrauduRoi)and3.7(stationMonaco).The equitabilityindex(Fig.3d),whichgivesinformationaboutthedom- inanceofoneormoretaxa,variesbetween0.53(stationGraudu Roi)and0.96(stationMarseilleGrandeRade).Accordingtothese indices,biodiversityseemstoincreasetotheeasternpartofthe FrenchMediterraneancoast,wherethedepthofthesamplingsta- tionsismoreimportant.Thereisindeedastatisticallysignificant positivecorrelationbetweenthediversityindicesandwaterdepth (r=0.79forES50,r=0.74for Shannon–Wienerindex,r=0.66for specificrichness,andr=0.52forequitabilityindex,p<0.05forall correlations;AppendixC).

Theexpectednumberofspeciesfromasub-sampleof50indi- viduals(ES₅₀,Fig.3e)exhibitssmallerdifferencesbetweenstations comparedtouncorrectedspeciesrichness.Ingeneral,stationswith relativelylowtotalfaunaldensities(e.g.Cerbère,MarseilleGrande Rade or Porquerolles) deviate less from theoverall trend. This observationconfirmsthegoodperformanceoftheES₅₀indexin caseofsampleswithlargedifferencesinfaunaldensity,whichis alsothecasefortheShannon–Wienerandequitabilityindices.

The comparison of thediversity indices for the 0–1cm and 0–4cmintervalsshowsfirstthatonaverage8additionalspecies(a maximumof16species),havebeenfoundwhenthe1–4cminter- valisadded(Fig.3b).However,thedifferenceinShannon–Wiener andES50indicesbetweenthe2considereddepthintervalsisrela- tivelysmall(Fig.3candd).Speciesexclusivelyfoundinthe1–4cm sedimentintervalarerepresentedbyfewspecimens;thedensity differencesbetweenthe0–1and0–4cmlevelshighlightedinFig.3a aremainlyresultingfromanincreaseinthedensityofspeciesthat alsooccurinthefirstcentimetreofthesediment.Thestatistical comparisonofthediversityindicesofbothintervalsshowsasig- nificantdifferenceforthespecificrichness(t=−7.05,p=0.000)and Shannonindex(t=−2.71,p=0.02),butnosignificantdifferences for theequitability index (t=1.53, p=0.15) and ES₅₀ (t=−1.12, p=0.28).

3.3. Verticaldistributionoftotallivingforaminiferalfaunas

Oxygenprofileshavebeenmeasuredat11stations.Infact,over- lyingwater,essentialforoxygenprofiles,wasnotalwaysavailable whenweusedaReineckcorer.Atypicalexampleofanoxygenpro- fileobtainedatstationCarteauisshowninAppendixD.Oxygen saturationis93%inthebottomwatersandstartstodecreaseatthe sediment-waterinterface.Theoxygenconcentrationintheinter- stitialwatersdecreasesrapidlywithinthefirstmillimetresofthe sedimenttoreachanoxicconditionsat6mm.

Theverticaldistributionoflivingforaminiferaiscontrolledby theoxygenpenetrationdepthinthesediment,thegrainsize,the availabilityoflabileorganicmatterandbymacrofaunalbioturba- tion,thelatterparametermodifyingtheformerthree(e.g.Corliss, 1985;Shirayama,1984;CorlissandEmerson,1990).

Theverticaldistributionofforaminiferalfaunaswasstudiedat 14stations.Inordertogroupthese14stationsinfunctionofsed- imentgrainsize,weperformedaclusteranalysis(usingtheWard method)usingthedifferentmeasuredgrainsizefractions(percent- agesofparticles<63␮m,63–125␮m,125–250␮m,250–500␮m and >500␮m).Asaresult,we obtainedtwo groupsofstations:

groupAwithmuddytosiltysediments,andgroupBwithsandy sediments.InTable1,itcanbeseenthattheaveragelivingdepth (ALD₅/ALD₆)oftheliveforaminiferalfaunaisconsiderablyhigher forthesandystations(groupB)thanfortheclayey-siltystations (groupA)(Figs.4and5).

ForthestationsofgroupA,withclayey-siltysediment(Fig.4), faunas present a maximum density in the first centimetre of the sediment (oftenin the first halfcentimetre) followed by a Table1

Oxygenpenetrationdepth(OPD)andaveragelivingdepth(ALD5/ALD6)forstationswhereoxygenprofileswereperformedandaveragelivingdepthwascalculatedforcores of5or6cmlength(dependingontheslicing)inordertocomparetheALDxofdifferentstations.NB:ALD3forToulonandALD4forAgdeEst.Environmentalparametersare addedtocomparewiththeverticaldistributionofforaminifera.

Station OPD(mm) ALD5/ALD6(cm) Depth(m) %OM %<63␮m %63–125␮m %125–250␮m %250–500␮m %>500␮m GroupA

Grau 7 1.0 15 3.28 67.92 25.86 6.21 0.00 0.00

Toul – 1.1 43 7.52 50.90 11.59 4.84 2.82 29.85

Cart 6 1.3 10 5.91 80.80 13.07 6.14 0.00 0.00

Mjet 14 1.4 41 5.41 51.91 19.80 19.78 7.61 0.90

Nice 12 1.4 30 2.21 46.12 28.47 17.79 6.80 0.81

Bduc – 1.6 14 1.68 87.52 10.75 1.73 0.00 0.00

GroupB

Colli – 1.4 23 1.37 2.89 13.86 39.90 33.74 9.62

AgdE – 1.8 21 1.57 8.45 27.56 56.99 6.99 0.00

Maire – 2.0 40 3.31 4.82 4.26 11.22 23.28 56.42

Vfran – 2.0 42 3.99 14.66 12.25 18.11 22.75 32.22

Leuc – 2.2 22 1.72 19.73 53.10 24.61 2.41 0.14

Carry – 2.3 48 3.54 26.28 14.25 17.57 17.72 24.18

Ment – 2.3 51 1.73 28.26 37.50 32.75 1.49 0.00

Pamp – 2.7 42 2.78 19.10 6.06 11.39 23.95 39.49

Fig.4.VerticaldistributionoflivingforaminiferalfaunasforstationsofgroupA.Foraminiferaldensitiesarestandardisedfor50cm³.Majorspecies(>5%ofthetotalfaunaof thecore)arepresentedseparatelyfromtherestofthespeciesgatheredin“others”.NB:xandyaxesscaleschangeaccordingtothestations.

noticeabledecreasedowncore,moreorlesssharp.GroupAsta- tionsarecharacterisedbyarelativelyshallowaveragelivingdepth (ALD₅/ALD₆),from1.0to1.6cm(Table1).Thesestationshavea relativelyhighOMcontent,between1.68and7.52%(4.34%onaver- age).Thereisastrongnegativecorrelationbetweenthe<63␮m particlesize fractionandtheALDxof thetotalfauna(r=−0.57, p<0.03).Generally,silty-clayedmarineenvironmentsarecharac- terisedbyweakhydrodynamicsallowingthedepositionoforganic matter(Tyson,1995)anditsadsorptiononclayparticles(Hedges andKeil,1995).Fine-grainedsubstratescanthereforeoftenbecon- sideredaseutrophictomesotrophicenvironments.

The strong surface maximum, together with poorfaunas in deeper sediment layers found at these stations is typical for eutrophicenvironmentswithlimitedoxygenpenetrationdepth(a maximumOPDof14mmforstationswhereoxygenprofileswere performed)(Jorissenetal.,1995).

AlsoforthestationsofgroupB(Fig.5),theforaminiferalverti- caldistributionisgenerallycharacterisedbyadensitymaximum inthefirstcentimetreofsediment.However,unlikegroupA,den- sitiesremainhighindeepersedimentlayers.Consequently,the

ALD₅/ALD₆ of these stations is muchhigher (between 1.4 and 2.7cm,2.1cmonaverage;Table1).

Forsomestations(e.g.AgdeEst,Leucate),thefaunaldensityand compositionarealmostthesameineverysedimentlayerdownto 5cm.ThestationsofgroupBaregenerallycharacterisedbyalower OM,of2.5%onaverage(1.37–3.99%).

Unfortunately,nooxygenmeasurementscouldbeperformed forthestationsofgroupB.However,theabundantfaunasindeeper sedimentlayerssuggestthatoxygenpenetrationisconsiderably deeperherethanatthestationsofgroupA,whereoxygenpenetra- tionvariesfrom6to14mm(Table1).

3.4. Speciescompositionoflivingforaminiferalfaunas

In total, 40 major species (>5% in at least one station, 150–500␮m)havebeenidentified:20perforate,8porcelaneous and12agglutinatedtaxa(Table2,seePlates1–4inSupplemen- tarymaterial1forplatesshowingMEBpicturesofmajorspecies, Supplementarymaterial2forstandardisedcountingdataandSup- plementarymaterial3forthetaxonomicallistofmajorspecies).

Fig.5.VerticaldistributionoflivingforaminiferalfaunasforstationsofgroupB.Foraminiferaldensitiesarestandardisedfor50cm³.Majorspecies(>5%ofthetotalfaunaof thecore)arepresentedseparatelyfromtherestofthespeciesgatheredin“others”.NB:xandyaxesscaleschangeaccordingtothestations.

Table2

Listofmajorspecies(relativedensity>5%inatleastoneofthestationsstudiedbetween0and1cm).

Perforatespecies Porcelaneousspecies Agglutinatedspecies

Name Abbrev. Name Abbrev. Name Abbrev.

Ammoniabeccariif.beccarii Abecc Adelosinalongirostra Along Ammoscalariapseudospiralis Apseudo

Asterigerinatamamilla Amami Biloculinellairregularis Birreg Eggerellascabra Escab

Astrononionstelligerum Astel Quinqueloculinaaspera Qasp Lagenamminasp.a LagenamA

Buccellagranulata Bgran Quinqueloculinabosciana Qbosc Lagenamminasp.b LagenamB

Buliminaaculeata Bacul Quinqueloculinacostata Qcost Leptohalysisscotti Rscot

Cancrisauriculus Cauri Quinqueloculinaseminula Qsemi Psamosphaerafusca Pfusc

Cibicideslobatulus Cloba Sigmoilinagrata Sgrata Reophaxfusiformis Rfusif

Elphidiumcrispum Ecris Triloculinatrigonula Ttrigo Reophaxmicaceus Rmica

Elphidiumgranosum Egran Reophaxscorpiurus Rscorp

Elphidiumpoeyanumf.decipiens Epoey Reophaxsubfusiformis Rsubfus

Hanzawaiaboueana Hboue Textulariaagglutinans Taggl

Neoconorbinaterquemi Nterq Textulariasagittula Tsagit

Noniondepressulum Ndepres

Nonionscaphum Nscap

Nonionellaturgida Nturg

Planorbulinamediterranensis Pmedit

Rectuvigerinaphlegeri Rphle

Rosalinaglobularis Rglob

Spirillinasp. Spiril

Valvulineriabradyana Vbrad

Therelativedensitiesofthesemajorspeciesdonotshowasta- tisticallysignificantdifferencebetweenthe0–1and0–4cmlevels (AppendixE).Thisresultindicatesthatthepercentagesofthedomi- nanttaxaofthefirstcentimetrecanbeconsideredasrepresentative forthewholefauna.Thefollowingdiscussionisthereforeuniquely basedonthe0–1cmlevel.

Amongthe40majorspecies,10areverycommoninthestudy area,andarepresentinmorethan70%ofthestations:2perfo- ratetaxa(Ammonia beccarii,Buccella granulata),4 porcelaneous taxa(Adelosinalongirostra,Quinqueloculinaaspera,Quinqueloculina seminula,Triloculinatrigonula)and4agglutinatedtaxa(Eggerella scabra, Lagenammina spp., Reophax fusiformis, Textularia agglu- tinans). More specifically, Eggerella scabra is clearly the most commonspecies sinceit ispresent in26of the31stations;15 stationswithrelativedensities over 5%and7 stationswhere it representsmorethan30%ofthetotalfauna.

On thecontrary,somestationsarecharacterisedbya strong relative abundance of species that are not frequentlyfound at otherstations.Forexample,Elphidiumcrispumisdominantatthe stationGrauduRoiwhereitrepresents54.6%(1142specimensper 50cm²).Thisspeciesshowsonlyverylowabundances(lessthan 15specimens)in13otherstationsandisabsentintherestofthe stations.StationLeucatepresentsalsoapeculiarfaunalcomposi- tioncomparedtootherstudiedstationswithhighrelativedensities ofNoniondepressulum(18.4%)andNonionellaturgida(16.1%),these speciesbeingveryscarceinotherlocationsexceptatGrauduRoi.

Leucateis alsocharacterisedbyarelative abundanceof6.7%of Leptohalysisscotti,which appearsonlywithsingleindividualsin 3otherstations.

The analysis of thecorrelations betweenthe availableenvi- ronmentaldataandtherelativedensitiesofthemajorspeciesis giveninAppendixF.Sinceourstudyconcernsaverylargearea withstronglycontrastingenvironmentalcharacteristics,itmaybe expectedthatalsothefaunalcompositionwillshowlargediffer- encesbetweenstations.Forexample,thepositivecorrelationof Noniondepressulumand Nonionellaturgidawiththe63–125␮m grainsizefractionismainlydeterminedbytheirhighpercentages atstationLeucate,whichischaracterisedby53%ofveryfinesand (63–125␮m).Atotherstationswithsimilarsediment grainsize (e.g.IleEmbiez,AgdeOuest),thesetaxaaremuchlessfrequentor absent.Consequently,itbecomes difficulttoworkwithindivid- ual(marker)speciesandtoobserveclearrelationsbetweensingle speciespercentagesandenvironmentalparameters.Itistherefore

morerelevanttodefinegroupsofspecieswithasimilardistribu- tion,whichwillrespondin thesamewaytotheenvironmental parameters.

SeveraltrialswithQ-andR-modemultivariatestatistics(Prin- cipal ComponentAnalysis,cluster analysis)toconstructspecies clustersonlyyieldedveryinconclusiveresults.Q-modePCAresults showthatElphidiumcrispumandEggerellascabraareresponsiblefor mostofthevariabilityinthedatasetwhenconsideringthetwofirst PCAaxes(seeSupplementarymaterial4).Thisisduetothestrong dominanceofElphidiumcrispumatstationGrauduRoiandthehigh relativedensitiesofEggerellascabraatanumberofstations.These speciesalsostandoutintheR-modePCA.Theotherspeciesclus- tertogether,anddonotformclearspeciesgroups,evennotwhen consideringthenextaxes.Faunalclusterssystematicallycontaina mixofspecieswithdifferentecologicalcharacteristics,andwere thereforeverydifficulttointerpretecologically(seeSupplemen- tarymaterial5).Forthisreason,wepreferredtotestthreeapriori groupings,basedon:(1)wallstructure,(2)lifeposition(epiphytic species),and (3) literatureobservations ontolerance/sensitivity withrespecttoeutrophication.

3.5. Speciesgroupsindicativeofenvironmentalquality

Accordingtothecomparisonbetween0–1cmand0–4cmsed- imentintervalsfordensity,diversityandspeciescomposition(see paragraph5.1formoredetails),weconsideredonlydatafromthe firstcentimetreofthesedimentforthestudyofgroupsofindicative speciesofenvironmentalquality.

3.5.1. Speciesgroupsaccordingtowallstructure

Aternarydiagram(Fig.6,afterMurray,1973)presentsthecon- tributionofthe3maingroups(definedbywallstructure)tothe foraminiferalfaunas(ofthe0–1cmlevel):perforate,porcelaneous andagglutinatedspecies(seealsoAppendixB).StationCollioureis theonlyoneshowingamajorityofporcelaneoustaxa(Fig.6,upper bluetriangle).ThefaunasofstationsToulonGrandeRade,Marseille GrandeRade,IlePlane,Porquerolles,MarseilleJetée,Carry,Fosand GrauduRoi arecomposedinmajorityofperforateforaminifera (Fig.6,lowerrightredtriangle)whereasstationsNice,AgdeEstand Ouest,Gruissan,SèteandIleEmbiezarecharacterisedbyadomi- nanceofagglutinatedtests(between54and71%;Fig.6,lowerleft greentriangle).AtstationBeauduc,whereporcelaneoustaxaare almostabsent,equalamountsofperforateandagglutinatedtaxa

Fig.6.Ternarydiagramrepresentingstationsaccordingtothefractionsofthe3maingroupsofforaminifera(perforate,porcelaneousandagglutinatedtaxa)intheliving faunainthe0–1cminterval.Stationsdominatedbyperforateforaminiferaplotintheredarea(lowerrighttriangle),thosedominatedbyporcelaneoustaxainthebluearea (uppertriangle),andthosedominatedbyagglutinatedtaxainthegreenarea(lowerlefttriangle).(Forinterpretationofthereferencestocolorinthisfigurelegend,thereader isreferredtothewebversionofthisarticle.)

arefound.Theremainingstationsdonotshowacleardominance ofoneofthegroups.

Weperformeda canonical correspondence analysisto com- paretheavailableenvironmentalparameters(grainsizefractions, OMcontentand waterdepth) withthepercentageofthethree wall structure groups. The result shows that the five distin- guishedgrainsizefractionsaredistributedinahorseshoepattern

(Fig. 7). The percentageof porcelaneous taxa is plotted in the sameareaasmediumsand(250–500␮m),andisopposedtothe percentages of clay and silt.In fact, there is a significantposi- tivecorrelationbetweenthepercentageofporcelaneoustaxaand the fine and medium sand fractions (for 125–250␮m, r=0.57, p<0.05;for250–500␮m,r=0.55,p<0.05)andanegativecorre- lationwiththeclay/siltfraction(r=−0.71,p<0.05;AppendixC).

Fig.7. Canonicalcorrespondenceanalysis(axis1vs.axis2)performedonenvironmentalparametersandthepercentagesofthe3mainforaminiferalgroups(without consideringMarseilleGrandeRadeandCapCanailleforwhichnoenvironmentaldatawereavailable).

Thepercentageofperforateforaminiferaplotsinthesameareaas OMcontentandwaterdepth;thereisindeedapositivecorrelation betweentheirpercentageandthepercentageofclay/silt(r=0.42, p<0.05)andwiththeOMcontent(r=0.50,p<0.05;AppendixC).

Finally,thepercentageofagglutinated taxa plotstogether with the63–125␮mfractionshowinga positivecorrelation(r=0.47, p<0.05). Thisgroupanti-correlateswithcoarsesand(>500␮m, r=−0.52,p<0.05).Ingeneral,thedistributionofthisgroupseems tobeoppositetotheoneoftheperforatetaxa(r=−0.74,p<0.05;

AppendixC).

3.5.2. Speciesgroupaccordingtolifeposition(epiphyticspecies) Toconstitutetheepiphyticspeciesgroup(i.e.capabletolive fixedonalgae),weselectedthespeciesclassifiedinmorphotypes AandBasdefinedbyLanger(1993).Thesemorphotypeshavebeen definedaccordingtothedifferentmodesofsurfaceattachmentand thefeedingstrategies.MorphotypeArepresentsstationary,perma- nentlyattachedspecieswhichsecreteanorganicsubstancetoglue toseagrassleavesoralgalblades(e.g.Planorbulinamediterranen- sis).MorphotypeBrepresentstemporaryattachedspecieswhich haveatrochospiralshapewithaperturesfacingthesubstrate(e.g.

Rosalinaglobularis).MorphotypesCandDarenotconsideredinour groupofepiphyticspeciessincetheycanalsoliveinareaswithout seagrassoralgaeconsideringtheirpermanentlymotilebehaviour (e.g. elphidiids, porcelaneous species). The epiphytic species

identified in our samples are Asterigerinata mamilla, Cibicides lobatulus,Gavelinopsispraegeri,Hanzawaiaboueana,Neoconorbina terquemi, Planorbulina mediterranensis, Rosalina bradyi, Rosalina globularis, Rosalina vilardeboanaand otherRosalina species (e.g.

Jorissen,1987;Kitazato,1988;Langer,1993;Barmawidjajaetal., 1995;Schönfeld, 2002;Murray,2006; Buosietal.,2012).These epiphytic species are indicative of the presence of vegetation in thevicinity of thesamplingstation and generally ofa good ventilationofbottomwaters.AccordingtovanderZwaanetal.

(1999), many epiphytic species are sensitiveto oxygen-limited conditions and would be competitive in oligotrophic environ- ments.Theyaremainlyfoundinsandysediments(Pujos,1976;

Spindler, 1980; Bizonand Bizon, 1984; Jorissen,1987; Murray, 1991;VillanuevaGuimeransandCerveraCurrado,1999;Mendes etal.,2004;Mojtahidetal.,2006)andsomeofthesespecies,suchas CibicideslobatulusandG.praegeri,cantoleratehighenergyenviron- ments(CoppaandDiTuoro,1995;GuimeransandCurrado,1999;

Schönfeld,2002;Panierietal.,2005;Martinsetal.,2007;Milker et al.,2009).In ourstudyarea, thePosidoniameadows provide abundantnichesfortheseforaminiferalspecies;therhizomesactas sedimenttrapsandtheleavesareoftencolonisedbymotileor(tem- porarily)fixedepiphyticforaminifera(Vénec-Peyré,1984;Langer, 1993).

Wecalculatedthecumulativepercentageofepiphyticspecies forthe0–1cmintervalofthe31studiedstations(Fig.8a,Appendix

Fig.8.Percentageofindicativespeciesinthesample(0–1cminterval)ateachstation(West-Easttransect):(a)epiphyticspecies,(b)sensitivespecies,and(c)stress-tolerant species.

B).Fig.8ahighlightsagainthecleardifferencebetweenwestern shallowstationsandeasterndeeperstations(limitbetweenFosand Carry),withtheexceptionofAntibesNordandNicewereepiphytic speciesareabsent.AsillustratedbytheCCAanalysis(Fig.9),thereis apositivecorrelationbetweenthepercentageofepiphyticspecies andwaterdepth(r=0.53,p<0.05),mediumandcoarsesediment (for250–500␮m,r=0.40,p<0.05;for>500␮m,r=0.80,p<0.05).

Ontheotherside,thereisanegativecorrelationwithfinesands (63–125␮m;r=−0.50,p<0.05;AppendixC).

3.5.3. Speciesgroupsaccordingtotolerance/sensitivitytoorganic enrichment

Accordingto theliterature, we defined two species groups:

(1) a groupof“stress-tolerant” species, witha highpercentage beingindicativeofstressedconditions,suchaseutrophicationor abundantsuppliesoffine-grained sediments,and(2)a groupof sensitivespecies,whicharesupposedtobeindicativeofagood overallqualityoftheecosystem,andwhichshoulddisappearwhen environmentalconditionsbecomemorestressful.

Tenstress-toleranttaxa wereidentifiedonthebasisof liter- atureevidence:Buliminaspp.,Cancrisauriculus,Nonionscaphum, Noniondepressulum,Nonionellaturgida,Nonionellastella,Pseudoe- ponidesfalsobeccarii,Rectuvigerinaphlegeri,Valvulineriabradyana andtheagglutinatedLeptohalysisscotti(seePlate2inSupplemen- tarymaterial1).Theobservationspresentedintheliteraturewhich supportedourdecisiontoplacethese10taxainthetolerantgroup arelistedinAppendixG.

Thegroupofsensitivespecies(seePlate3and4inSupplemen- tarymaterial1)includesallporcelaneousspeciesandallepiphytic species.Inaddition,wealsoincludedothermotileepiphyticspecies (morphotypesCandDaccordingtoLanger,1993)suchasElphidium species(E.crispum,E.granosumandE.poeyanum),Reussellaspinu- losaandSpirillinaspp.Accordingtotheliteraturethatsupportsour choicetogroupallthesespeciessensitivetostressedconditions (seeAppendixGforliteraturereferencesonwhichthisgrouping wasbased),apoorrepresentationofthisgroupinthetotalfauna

wouldbeindicativeofenrichmentinmuddysediments,eventually leadingtolowoxygenconditions.

Amongthe40majorspeciesidentified,14specieshavenotbeen assignedtooneofthesetwogroups,eitherbecausetheyareneither sensitivenorstress-tolerant,orduetoalackofwelldocumented studieswithclearpollutiongradients,orduetocontradictorylit- eraturedatawithrespecttotheirecologicalcharacteristics.

The caseof Eggerellascabraisparticularlystriking.Although thisspecieshasbeenreportedinseveralarticlesasbeingableto toleratestressedconditions,wedidnotincludeitinthegroupof tolerantspecies.Eggerellascabraisacontinentalshelfspecies(e.g.

Murray,1991;Barmawidjajaetal.,1992)thatlivesinmuddyto sandysubstrates(Murray,1986;AlveandNagy,1986;Scottetal., 2003)andinvariousmicrohabitats,fromtheoxygenatedsediment surfacetothedeepestanoxiclayers(e.g.Barmawidjajaetal.,1992;

Jorissenetal.,1992;Ernstetal.,2002,2005;Duijnsteeetal.,2003, 2004).Itappearsthereforetobetolerantforhypoxicconditions.

Forinstance,EggerellascabraiscommonintheAdriaticSea,inareas whereimportantamountsofdegradedorganicmattercauseoxy- gendepletion(DonniciandSerandrei-Barbero,2002).Ithasalso beenshowntosupportextremelypollutedenvironmentsinSor- fjord,westernNorway(Alve,1991).Ontheotherhand,thisspecies isverycommonandtypicalinmanyapparentlyunpollutedcoastal Mediterraneanenvironments(e.g.Vénec-Peyré,1984;Donniciand Serandrei-Barbero, 2002; Duijnstee et al., 2003; Frontalini and Coccioni,2008;Mojtahidetal.,2009;Goineauetal.,2012;Sabbatini etal.,2010,2012).Severalauthorssuggestedthatthisspecieshas apoorertolerancetostressedconditionsthansomeclearoppor- tunists,althoughithasagreatabilitytowithstandfluctuationsin diverseparametersincludinganabsenceoflabileorganicmatter (Scottetal.,2003;Mojtahid,2007;deNooijeretal.,2008;Sabbatini etal.,2012).Finally,someauthorshaveconsideredEggerellascabra asanepiphyticspeciesonseagrass(RedoisandDebenay,1996;

Debenay,2000),againsuggestingthatitcanbeadominantfaunal elementinhighqualityecosystems.Becauseofthisstronglycon- trastingevidenceandthehighdensitiesofEggerellascabrainmost

Fig.9.Canonicalcorrespondenceanalysis(axis1vs.axis2)performedonenvironmentalparametersandthepercentagesoftheindicativespeciesgroups:epiphyticspecies, stress-tolerantandsensitivespecies(withoutconsideringMarseilleGrandeRadeandCapCanailleforwhichnoenvironmentaldatawereavailable).

ofourstudiedstations,wedecidednottoincludethisspeciesin ourstress-tolerantgroupsothatitdoesnotobscurethemessage givenbymoreclearstress-tolerantspecies.

Fig.8band cshows thepercentagesof sensitiveand stress- tolerantspeciesinourstudyareafollowingaWest-Easttransect.In ourdataset,thepercentageofstress-tolerantspeciespositivelycor- relateswiththepercentageoffineparticles(r=0.48,p<0.05)and organicmatter(r=0.40,p<0.05;Fig.9,AppendixC).Conversely, stress-tolerantspeciesareweaklyrepresentedineasternstations, inspiteofhighorganicmattercontentsmeasuredatsomestations (e.g.stationsFréjusandAntibes).

Conversely, sensitive species are negatively correlated with thepercentageof fine particles (for<63␮m, r=−0.49, p<0.05;

for63–125␮m,r=−0.44,p<0.05)andpositivelycorrelatedwith coarserparticles(for250–500␮m,r=0.59,p<0.05;for>500␮m, r=0.60,p<0.05;Fig.9,AppendixC).

4. Discussion

4.1. Representativityofthefaunaofthefirstcentimetreof sediment

Ecological studies of recent foraminiferal faunas are usually basedontheanalysesofthetotalfaunainthesedimentcolumn, downto 5 or 10cm depth. In fact, the vertical distribution of foraminiferacangiveinformationabouttheecologicalstrategies ofdifferentspeciesorabouttheenvironmentalconditions.Inour study,thefaunaofdeepersedimentlayersallowsustodistinguish twotypesofenvironments.Moreeutrophic,silty/clayeystations withalimitedoxygenpenetrationdepthhavethelargemajorityof thefaunainthetopmostcentimetre,whereassandystations,prob- ablywithlowerorganicmattersupplies,showamoreevenfaunal distributioninthefirst2to5cmofthesediment.

Althoughthisenvironmentalinformationisnotwithoutinter- est,thesignificantlylongerpickingtimerequiredtoobtaindata fromdeeperlayermakesthatthestudyoftheverticaldistribution analysisishardlypossibleforbio-monitoringstudies,inwhicheco- nomicalaspectsareimportant,andstrictdeadlineshaveoftento berespected.Recently,theFOBIMOgrouprecommendedthere- foretolimitforaminiferalbio-monitoringstudiestotheanalysis ofthefirstcentimetreofthesediment.Thisrecommendationwas supportedbytheresultsofBouchetetal.(2012),whostudiedthe faunalresponsetovariousoxygenconcentrationsintheNorwegian Skagerrak,usingdiversityindicesbasedonthefaunasinthe0–1cm and0–2cmintervals.Itturnedoutthattheresultswerevirtually similar,suggestingthatthestudyofthe0–1cmwassufficient.

However,beforetakingthedecisiontorestrictthefaunalanal- ysistotheuppermostcentimetre,wewantedtoverifywhether thisdoesnotleadtoanerroneousorincompleteinterpretationof thefaunalresponsetoenvironmentalconditionswhenconsider- ingourcoastalMediterraneansamples.Inourstudyarea,species livingexclusively in deepersediment layers (e.g.Corliss, 1985;

Jorissenetal.,1995)werenotobserved(Figs.4and5).Buzasetal.

(1993)highlightedthefactthatthemicrohabitatsuccessionusu- allyobservedindeepwater(outercontinentalshelfandslope)is muchlessevidentoninnercontinentalshelfenvironments.They explainedthisdifferencebythemoredynamicnatureofcoastal areas(sedimentdisturbance,bioturbation,etc.).

Toknowifastudyrestrictedtothefirstcentimetreofsediment (generallycontainingthemajorityofthelivingfauna)issufficient tocorrectlydefinetheenvironmentalquality,wecomparedfaunal parametersbetween0–1and0–4cmintervals.Statisticalcompar- isonofequitabilityindicesandES₅₀shownosignificantdifference between0–1and 0–4cm. However,faunaldensities aresignifi- cantlydifferent.FortheShannonindex,thestatisticaltestidentified

significantlyhighervaluesforthe0–4cminterval(testbasedonthe signofthedifference).However,thedifferencesaresmall(average shiftbetweenthevaluesfrom0–1and0–4cmintervalsof0.11),and wouldnotcausemajorchangesintheclassificationofthestations intothedifferentqualitycategories.Itisalsointerestingtoobserve thattherearenosignificantdifferencesin therelativedensities ofmajorspecieswhichchangeonlyslightlybetweenthe0–1and 0–4cmintervals(Wilcoxontest,AppendixE).

Inviewofalltheseresults,weconcludethatinourstudyarea, thefirstcentimetreofthesedimentgivesaverygoodpictureof theoveralllivefauna,itsdiversityandcomposition.Therefore,our resultsfullysupporttherecommendationoftheFOBIMOgroup (Schönfeldetal.,2012).

4.2. Relevanceofthevariousfaunalparametersforecosystem qualityevaluation

Ideally, thedevelopmentofa faunalindex ofenvironmental qualityshouldbebasedonapreciseknowledgeofpollutionsources andintensitiesinthestudyarea.Theanalysisoffaunalpatterns alongawell-describedpollutiongradientmakesitpossibletodis- tinguishspecieswithvariousdegreesoftolerance,andtoidentify the faunalparameter(s) or indices that correlate best withthe stateoftheenvironment,asdefinedbytheconcentrationofone ormorepollutants.Usually,suchstudiesfocusontheimpactofa singlestressparameterontheforaminiferalfaunas,suchasbottom water oxygen concentration(Bouchet et al., 2012), eutrophica- tion(Mojtahidetal.,2008),orchemicalpollution(Frontaliniand Coccioni,2008;Mojtahidetal.,2006).Inourstudy,thegeograph- icalareaofconcernisverywide,pollutantsaredispersed inan erraticway,andtheirconcentrationisnotknown.Consequently, wedonotdisposeofacleartransectfollowingapollutiongradient, andourapproachhasthereforetobeslightlydifferent.Wecannot havetheambitiontodirectlydevelopabioticindex,butinstead,we willtrytodeterminewhichfaunalparameterscouldberelevantto adequatelydescribetheecosystemhealth.

4.2.1. Biodiversityindices

Accordingtodifferentdiversityindicescalculated,biodiversity seemstobehigherattheeasternpartoftheFrenchMediterranean coast. Unfortunately, becauseof the strong positive correlation betweendiversityindicesandwaterdepth,itisimpossibletosay whetherthehighervaluesofthediversityindicesoftheeastern stationsindicateahigheroverallbiodiversity,orwhethertheyare theresultofasamplingbias(shiftinwaterdepth).

Diversityindicesgiveimportantinformationaboutbiodiversity andfaunalequilibriumatastation.It hasbeenshown thatbio- diversityindicesmaybeusefultoclassifytheecosystemquality instronglypollutedconditions(e.g.Bouchetetal.,2012;Armynot duChateletetal.,2004).Ourstudyareadiffersfromtheseverely stressedenvironmentsdescribedbytheseauthors,becauseofthe absenceofaclearstressparameter,suchasoxygendepletionor heavy metal pollution. In fact, the French Mediterranean coast is generally considered as rather oligotrophic (e.g. Bosc et al., 2004).Consequently,aslighteutrophisationofthebenthicecosys- tem does not necessarily lead to a decreased biodiversity, but couldeasilycauseanincreaseofthevaluesofdiversityindices.

Basedonseveralstudiesofmacrofaunaalongagradientoforganic enrichment,thePearson–Rosenbergmodel(alsocalledSABmodel, PearsonandRosenberg,1978)clearlyshowsthataslightincrease inorganicmattercontentleadsfirsttoanincreaseofthenumberof species.Severalearlierstudiesshowthatforaminiferaldiversityis decreasingalongbathymetrictransectsinresponsetoloweringof theOMfluxtowardsgreaterwaterdepth(e.g.Rathburnetal.,1996;

Schmiedlet al.,2000; Fontanieretal., 2008).Consequently, we thinkthatintheoligotrophicMediterraneansea,diversityindices