Copepods Come in First: Rapid Colonization of Newly Constructed Temporary Ponds

Dagmar Frisch1,2

Andy J. Green1

1WetlandEcologyGroup, EstaciónBiológicadeDoñana-CSIC,Avda MaríaLuisas/n,E-

41013 Sevilla,Spain

2Author for correspondence,email:

Abstract

Thesequenceinwhichnewcolonistsreachanemptyhabitatcanbecrucialfor future developmentandspeciesstructureofcommunities.Itisthereforeimportanttoassess species compositionandabundanceintheinitialstagesofhabitatexistence.In thepresentstudywe focussed on colonizationof newlyconstructedtemporaryponds inDoñana,SouthwestSpain, createdby removing30 or 60 cmof topsoil.Toconfirmthatno egg-bankwas present,we conductedhatchingexperimentsusingsedimentcoresfromsixnew ponds andtwo reference sites.Hatchingwas notrecordedinthesedimentof thenew ponds withtheexceptionof two rotiferindividuals.In contrast,inthereferencesitesa maximumof 103 individualsper

samplehatched,includingcyclopoids,cladocerans,ostracodsandrotifers.In thefield,water sampleswerecollectedfromsevenponds after19 days of theirfirsthydroperiod.Cyclopoid copepods,mostlyMetacyclops minutus, hadarrivedanddominatedallsampledponds. Other taxawerethemonogonontrotiferBrachionus plicatilisinfour ponds, andthecladoceran Moina brachiata inonepond. Theabundanceof zooplanktonwas negativelycorrelatedwith conductivity,suggestingthatponds withhigherconductivityundergodelayedcolonization. We suggest thatfastdispersalanddominanceof certaincyclopoidcopepodsduringearly colonizationisrelatedtotheirabilitytostorespermandfastindividualdevelopment.Given thatcyclopoidcopepodscansurvivedroughtperiodsinthesedimentof temporaryponds, first andearlycolonizationby cyclopoidsislikelytohaveaprofound effecton thepropagulebank andfutureplanktoncommunitieswhenthepondsrefill.

Introduction

Rotifersandcyclopoidcopepodsareamongthefirstzooplanktontocolonize experimentaltanks(COHENSHURIN2003, CÁCERESSOLUK2002, JENKINSBUIKEMA

1998). JENKINSBUIKEMA(1998) found that,innewlycolonizedexperimentalponds, copepodsweresecondinnumberandbiomasstorotifers.Althoughcladoceranshave generallynotbeenfound toenterexperimentalponds or mesocosmsuntilthethirdmonthof theirexistence,ithas recentlybeensuggestedthatcladoceransarefasterdispersers than copepods(DEJENetal.2004).

Priorityeffectsof initialzooplanktoncolonistsmaystronglydeterminespecies composition(ROBINSON DICKERSON1987, JENKINSBUIKEMA1998). Experimental introductionof zooplanktonspeciesintoestablishedaquaticcommunitiesindicatesthatlocal biologicalinteractionsmightprecludeinvasionofexistingcommunities(SHURIN2000). The arrivalsequenceof speciesisthusacrucialfactorshapingthestructureof zooplankton communities,anditisimportanttostudycolonistspeciesandtheirabundanceduringthefirst weeks of habitatexistenceinordertounderstandthedeterminantsof communitystructurein thelongterm.

Thecolonizationby cladoceransof newlycreatedponds inBelgiumhas recentlybeen studied,beginninginthethirdmonthof pond existence(LOUETTEDEMEESTER2004, LOUETTEDE MEESTER2005). In contrast,despitetheobviousspeedwithwhichsome cyclopoidcopepodsenterexperimentalsystems(JENKINSBUIKEMA1998, CÁCERES& SOLUK2002), littleisknown abouttheircolonizationof new habitatsundernaturalconditions inthefield.Themainmodesof dispersalof copepodsremainsunclear,althoughthe possibilitiesof bird,insectandwind mediateddispersalhavebeensuggested(FIGUEROLAGREEN2002, HAVELSHURIN2004, GREENFIGUEROLA2005), as wellas dispersalvia hydrologicalconnections(MICHELSetal.2001, FRISCHTHRELKELD 2005).

Isolated,newlyconstructedponds thatfillwithrainwaterofferanidealopportunityto studyinitialcolonizationandcommunitysuccession.Whileapropagulebankstartstobuildup duringthefirstyearof existenceof new ponds(LOUETTEDE MEESTER2005, VANDEKERKHOVEetal.2005), thesedimentof olderwaterbodiescontainsdormantstagesof majorzooplanktontaxaandisanimportantsourcefor annualrecruitment(HAVELetal.2000, GYLLSTROMHANSSON2004). Thedormancystagediffersbetweentaxa:restingeggs are generallyproducedby rotifers,cladoceransandcalanoidcopepodswhileinothercopepodtaxa dormancyisexpressedin moreadvanceddevelopmentalstages,e.g.incopepodidsor adultsof cyclopoids,andinadultsof harpacticoids(GYLLSTROMHANSSON2004, SANTER

1998).

For thepresentstudywe used asetofnew temporaryponds inDoñana,Southwest Spain.For pond construction,30 or 60 cmof thetopsoilwereremoved.Giventherich diversityof zooplanktonpresentintemporaryponds of Doñana(FAHDetal.2000, SERRANO

FAHD2005, FRISCHetal.2006), thereishighpotentialfor colonizationof thenew ponds. Weaimedtoconfirmtheabsenceof apropagulebankpriortofloodingby conducting hatchingexperimentsfrompond sediments.Secondly,we aimedtoassess species compositionanddominancestructureof thezooplanktonspeciespresentafterinitial colonizationintheearlieststagesof pond existence(within19 days). Thisgenerally representsthedepthin whichapropagulebank,ifpresent,islocated(GYLLSTROMHANSSON2004). Giventheevidencefrommesocosmstudies(JENKINSBUIKEMA1998,

CÁCERESSOLUK2002), we hypothesizedthatcyclopoidcopepodsandrotiferswould bethe mainearlycolonistsinthenew ponds. As faras weareaware,thisisthefirststudyofitskind inMediterraneanhabitats.

Methods

Study area

Caracolesestate(37º07’N, 6º31’W)isa formermarshlandareaof 2,700 ha,whichwas incorporatedintoDoñanaNationalPark inFebruary2004. Untilthenit hadbeencultivated mainlywithcerealsfor over20 years.Theareawaslevelledanddrainedby ditchesinthe

1970s. Untilthewinterof 2004-2005, waterbodieswerelimitedtodrainageditchesandsmall, highlyephemeralrainpools.Theregionalzooplanktonspeciespoolwas studiedinspring

2004, includingthenaturalmarshesandneighbouringwetlandsof Doñana(FRISCHetal.

2006). Betweensummer2004 andspring 2005, atotalof 96 ponds of threedifferent diameters (60, 125 and250 m)andtwo depths(30 and60 cm)wereexcavated(Fig.1, and SANTAMARÍA etal.2005). For pond construction,30 or 60 cmof soilwas removedacross the wholepond areaby heavymachinery,withanarrow,slopedborder(less than1 mwide). Lasertechnologywas used tolevelthebottomof theponds.

Doñanahas aMediterraneanclimatewithrainfallconcentratedbetweenOctoberand May. The2004-2005 winterfollowingpond constructionwas exceptionallydry, andmostof the96 new ponds didnotcontainwateratanytime.Precipitationoccurredbetween27

Februaryand1 March2005 duringwhichatotalof 43.2 mmof rainwaterwas recordedatthe meteorologicalstation30 kmnorthof thestudyarea(Aznalcazar,37º 09'10''N, 06º 16'19'' W, source:JuntadeAndalucia,ConsejeríadeAgriculturay Pesca).Rainwateraccumulatedin severalponds for thefirsttimesincetheirconstruction,coveringonlypartof thedesignated pond basin(Table1 andFig.2). TheshallowtemporarylakesLuciodeMarilópez(300 ha) and LuciodelLobo(120 ha)withintheDoñanaNationalPark werefloodedartificiallywith groundwaterduringwinterandspring for waterbirdmanagement.Bothlakesarelocated within 2 kmof thenew ponds, andareamajorpotentialsourceof colonists(Fig.1).

Sediment samples

Toconfirmtheabsenceof apropagulebankpriortoinundation,we sampledsediment of sixof the30 cmdeepponds on 26 October2005 (Fig.1). Theseponds werechosentobe representativeof all96 new ponds andthereforecontainedponds frombothnorthernand southerngroups. Theseponds hadnotheldsurfacewaterpriortocollectionof sedimentcores. Threereplicatesedimentcoreswerecollectedineachpond, alongatransectfromcentreto border,usingametalcorer(depth16 cm,diameter8 cm).For comparisonwiththepropagule banks of naturalsitesandtotestsuitabilityof hatchingconditions,sixreplicatesediment

coreswerecollectedineachoftwo referencesites(Fig.1) whentheyhadbeendry for four months:LuciodelLobo(25 October2005) andLuciodeMarilópez(27 October2005).

Eachcorewassubdividedintofour layers(0-4, 4-8, 8-12, 12-16 cm)andplaced separatelyintoplasticzip-blockbags toavoidcross-contamination.In thelaboratory,samples werefloodedinplasticcontainers(volume1 L)with500 mlofdechlorinatedtapwaterand homogenisedwithaspoon. Thecompletelysubmergedsampleswereincubatedfor seven

days inaclimatechamberat15ºC and12:12h light,toresemblefieldconditionsatthetimeof sampling.Theoverlyingwaterwas filteredafter3 and7 daysof incubationandthefiltrate preservedin30% ethanol.Due tospatialconstraintsintheclimatechamber,onlythesamples of thetop4 cmof allsampledreplicates(n=30)wereincubatedon thedayof sampling,while theothersamples(n=90)werestoredat15ºC inthedark,andincubatedsuccessivelywithin onemonthof sampling.Sixcontrolswithdechlorinatedtapwaterwereincludedwitheach trial,to monitorpossiblecross-contaminationor aerialcontaminationduringtheexperiment. Withtheexceptionof ostracodsandnaupliiof calanoidcopepods,hatchinganimalswere identifiedtogenus or specieslevel.Followingthehatchingexperiment,allsedimentsamples of thenew ponds werewashed overa100 μmmetalsieveandthefiltrateexaminedvisually for copepodidsor ephippia.

Water samples and faunal analysis

Watersampleswerecollectedon 17-18 March2005 insevenponds thathadhelda smallamountof waterfor 19 to20 days. Insomeponds severalpuddleswerepresent.Ponds driedup aboutoneweekaftersampling.Due totheshallowwaterdepthin mostponds (<5 cm),we used a500 mlplasticcuptosamplewithoutdisturbingthesediment.Sampleswere filtered(63μmnylonnet),andthefiltratepreservedin6% formaldehyde.Wherepossible,a volumeof 10 Lwas sampledineachpond (seeTable1). Whenseveralpuddleswerepresent, subsampleswerecollectedinseveralof theseandcombinedtothetotalvolume.Temperature, DO, conductivity,pH, pond depthandwatersurfaceareawererecordedduringsampling

(Table1). During themuchwetter2003-2004 winter(FRISCHetal.2006, FRISCHetal.

unpublisheddata)branchiopodsandcopepodswereidentifiedinanumberof samplesfrom temporarywaterbodieselsewherewithintheCaracolesestatepriortopond construction.The specieslistofthesesamplesisincludedhere(Table4) for comparisonbetweenpreviously establishedspeciesintheestate,andpioneerspeciescolonizingthenew ponds.

Adultswereidentifiedtospecieslevel,usingEINSLE(1993), ALONSO(1996) and KOSTE(1978). Allindividualswerecountedunderalightmicroscope.Juvenilecopepods were countedinsubcategories:calanoidnauplii,cyclopoidnauplii,copepodidstagesC1- C4, andfifthcopepodidstage(C5). Sampleswithless than400 individualsperlitrewerecounted withoutsubsampling.At higherdensities,subsamplesrepresentingatleast1/6thofthetotal samplewas counted.Thissubsamplealwayscontainedatleast200 individualsof themost frequentcategory(cyclopoidnaupliiinallcases).Thecompletesamplewas screened microscopicallytoencounterraretaxa.

Results

Hatching experiment

Of all72 sedimentsamples(18 coresby four depths)of sixnew ponds, two samples containedonehatchlingeach.Bothsampleswerefromreplicatecoresofpond 0N3 (sediment depth0-4 cm).Bothhatchlingswererotifers,oneindividualof Brachionus plicatilis OF Müller1786, andoneofB. calyciflorus Pallas,1766. No hatchingwas recordedintheother

70 samplesfromthenew ponds. In contrast,zooplanktonhatchedfromall12 coresfrom referencesites.A maximumof 62 and103 Ind/samplehatchedfromthetoplayer(0-4 cm)of coresfromLuciodeMarilópez(n=6cores)andLuciodelLobo(n=6cores),respectively. Hatchlingsincludedmonogonontrotifers(Brachionus angularisGosse,1851, B. plicatilis, B. quadridentatus Hermann1783, B. urceolaris OF Müller1773, B. variabilis Hempel1896), cladocerans(Alona rectangula (Sars,1862), Alonella excisa(Fischer,1854), Ceriodaphnia quadrangula (Müller,1874)), cyclopoidcopepods(Metacyclops minutus (Claus)1863), calanoidnaupliiandostracods(detailsinTable2). Themeannumberofhatchingindividuals was approximately6900 Ind/m2inLuciodeMarilópezand5800 Ind/m2inLuciodelLobo. Abundanceof individuals(Table2) hatchingfromthereferencesedimentsamplesdidnot differbetweenreferencesitesfor anyof thetaxaseparatelynor for thetotalnumberof hatchingindividuals(Mann-Whitney-Utest,p >0.05).Abundanceof hatchlingsfromthe deeperlayersof thereferencesiteswasgenerallymuchlower(Fig.3).

Visualexaminationof filteredsedimentconfirmedtheabsenceofpropagulesfromall replicatecoresof thenew ponds withtheexceptionof 0S3, whichcontainedephippiacf. Moina inthetop4 cm(7 and4 ephippiaintwo ofthethreereplicates).In contrast,thecores of thereferencesitescontainedlargernumbersof unhatchedpropagules(e.g.Daphnia and Moina ephippia,copepodeggs, ostracods),buttheirnumberwas notrecorded.

Colonization of newponds

Withintwo weeks, thenew ponds werecolonizedby copepods(Metacyclops minutus andMegacyclops viridis(Jurine)1820), rotifers(Brachionusvariabilis(Hempel,1896) and an unidentifiedmonogonontspecies)andcladocerans(Moinabrachiata(Jurine,1820)). Ostracods werenotrecorded.Whilecyclopoidcopepodswerepresentinthewaterof all ponds studied,rotiferswereonlyfound infour, andcladoceransonlyinoneof thesevennew ponds (Table3).

Thegroup of cyclopoidnaupliiwas by farthemostnumerous,followedindensityin mostponds by theearlycopepodidstagesC1toC4(Table3). Metacyclops minutuswasthe mostfrequentcyclopoidinthestudyarea(presentinfiveoutof sevenponds) whereas Megacyclops viridis onlyoccurredinonepond. Itcanbeassumedthatjuvenilestages belonged totherespectivecyclopoidspeciesrecordedinapond, as adultsof thesetwo species didnotoccurtogether.In allponds, therelativeabundanceof adultcyclopoidswas below3%. Themaximumdensityof juvenilecyclopoidsincludingnaupliiwas 1136 Ind/Linpond 6S3 (Table3). Althoughrotiferswerepresentinfiveponds,theirdensitieswerebelow2 Ind/L.

ThecladoceranMoina brachiata was onlypresentinonepondatlow density(0.2 Ind/L, Table 3). Boththetotalnumberof zooplanktonindividualsandthatof cyclopoidcopepods was significantlyandnegativelycorrelatedtoconductivity(Spearmancorrelations,R=- 0.83, p=0.01),butnottoanyotherenvironmentalvariablerecorded.

During spring 2004, whichprecededpond excavationandotherrestaurationmeasures, atotalof 13 crustaceanspecieswererecordedindrainageditchesandsmallpuddlesofthe Caracolesestate.Theseincludedfivecopepods,sixcladocerans,ananostracananda notostracan(Table4). Of thesecrustaceans,onlytwo speciescolonizedthenew ponds during thepresentstudy(Metacyclops minutus andMoina brachiata).

Discussion

ThecyclopoidcopepodMetacyclops minutus was thedominantfirstcolonistinthe new ponds. Althoughthisspeciesproducesdrought-tolerantrestingcopepodidstages(MAIER

1992) andcouldthushavehatchedlocallyfrompond sediments,our datasupport theabsence of localprogagulebanks priortoflooding,atleastfor cyclopoids.WhilenoMetacyclops minutus hatchedfromsedimentof thenew ponds, thisspeciesandotherzooplanktontaxa hatchedfromsedimentcoresofreferencesites,confirmingtheirsurvivalindry sediments duringJuly-October,withmaximumairtemperaturesof 44ºCinJulyand41ºC inAugust

2004, andalsoconfirmingthesuitabilityof theexperimentalhatchingconditions.Although two individualsof two rotifertaxahatchedfromoneofthenew ponds, itispossiblethata rotifereggbankdidnotexistimmediatelyafterpond constructionbutthateggs enteredthis pond by wind dispersal(HAVELSHURIN2004)duringthedry phaseof theponds. As the studyponds werebuiltinanareathathadbeendrainedfor over20 years,andthetop30 - 60 cmof soilhadbeenremovedtocreatetheponds, we suggest thatM. minutus andother zooplanktonspeciespresentcolonizedthepondsfromexternalsourcepopulations.Thehigh numberof ponds inneighbouringareaswhereMetacyclops minutus ispresent(FRISCHetal.

2006) mayhavefacilitateditsdispersalintothenew ponds. Thedispersalmodefor cyclopoid copepodsremainsunknown, althoughtransportby insectsandbirds havebeensuggested (HAVELSHURIN2004, GREENFIGUEROLA2005). Thestudyponds weretoosmall,dry andisolatedtoattractducks andotherwaterbirdsatthetimeof thisstudy,butwagtailsand otherpasserinesas wellas Odonataandotherinsectsfrequentlyvisitedtheponds. In addition tooverlandvectors,possibledispersalviahydrologicalconnectionsmustbetakeninto account,becausewe cannotruleoutthepossibilitythatapropagulebankwas presentinthe sedimentsadjacenttotheinundatedponds, so thatthecyclopoidscouldhaveenteredthe ponds viadrainagefromthesurrounding catchment.Thiswould beanalternativeexplanation for theobservedhighcolonizationratesofMetacyclops, althoughwe haveno evidencethat

rainfallwas heavyenoughtocausedrainageintotheponds, andthepoolspresentinthepond basins appearedtobeoriginatingfromdirectrainfall.However, dispersalviadrainagewould notexplainthestrong dominanceof cyclopoidsoverotherzooplanktonwhichareequally likely tobepresentinestablishedpropagulebanks,as evidencedby thediversityof taxa hatchingfromsedimentsof referencesitesandby thevarietyof speciesrecordedintemporary poolsinCaracolesestatebeforepond construction(Table4).

Toobtainanestimatednumberof colonistsperpond we modelledpopulationgrowth for M. minutus (Table5) usingdevelopmenttimesfromMAIER(1992). Due totheshort generationtimesof M. minutus, mostindividualsrecordedintheponds couldbeoffspring of afew founderfemales.Accordingtoour model,apopulationwith19050 naupliicanbe producedinthesecondgenerationwithin19050, startingwithonefertilizedfemale. Accordingtothisestimateandassumingfertilizedfemalestobethedispersalstage,the

numberof colonistsrequiredtoobtainthenumberof naupliiobservedwasbetween0.002 and

12.7 insixof sevenponds. In contrast,200 colonistsmustbeassumedfor pond 5S4, suggestingeitheramassivedispersaleventinthispond, or averypatchydistributionof naupliiduringsampling.Theestimatedvalueof 0.002 colonistsfor pond OS2 suggests this pond was colonizedmuchless than20 days beforesampling.Althoughtheseresultsmustbe interpretedwithcautionduetotheassumptionsinvolved,our resultssuggest ahigher colonizationrateforM.minutuscomparedtothefindingsof VANDEKERKHOVEetal.(2005), who estimatedaminimumrateof 7.2 ephippiapond-1year-1for cladocerans.

In cyclopoids,multipleclutchesmaybefertilizedby spermreceivedina single mating,duringwhichaspermatophoreisattachedtothefemale,makingre-mating unnecessary(MAIER1995). Thus anew habitatcanpotentiallybecolonizedby asingle fertilizedfemale.Wesuggest thatacombinationof theabilitytostorespermandfast developmentallowsomecyclopoidcopepodstobesuccessfulearlycolonists.Other cyclopoidgenerawithsimilarlyshort generationtimes,such asEucyclops or Tropocyclops areknown tobeamongthefirstzooplanktontocolonizenew waterbodies(EINSLE1993, CÁCERESSOLUK2002, JENKINSBUIKEMA1998, REIDJANETZKI1996). However, whetherponds werecolonizedby repeatedarrivalof cyclopoids,or whetherpopulationsare foundedby oneor few individualsshouldbeclarifiedinfuturepopulationgeneticstudies.

Despitethereportedcapabilityof Metacyclops minutus toinhabitawide salinity spectrumbetween0 and25 ppt(ALONSO1990), our resultssuggest adelayof colonizationin ponds withhighersalinities.Wefound anegativecorrelationbetweentheabundanceof cyclopoidcopepodsandconductivity,whileotherenvironmentalfactorsmeasuredhadno apparentrelationtotheabundanceof zooplankton.Negativerelationshipsbetweenabundance andsalinityhavebeenfound previouslyinothermicrocrustaceansinhabitingshallow Mediterraneanwetlands(GREENet al. 2005). Thisislikelytoberelatedtoalimited halotoleranceof mostfreshwaterzooplanktonspecies,whichoftenoccurwithincertain

rangesof salinity(ALONSO1990). Therefore,thearrivalofpropagulesinabrackishpond mightnottranslateintocolonization.Fecundityandhatchingratesof zooplanktoncanbe negativelyinfluencedby highconductivities(CASTRO-LONGORIA2003) thusreducing populationgrowth ratesof colonists.

Many cyclopoidcopepodshavethecapacitytorapidlycolonizethewatercolumnafter rehydration,bothby hatchingfromthecopepodidbankandby dispersingfromoutside

sources(FRISCH2002, FRISCHTHRELKELD 2005). Metacyclops minutushas longbeen known towithstandconsiderabledrought(CLAUS1894). Thedensityof dormantC4stages can reach1200 Ind /m2(MAIER1992). Theycanbeexpectedto bethefirstandfastestspecies torecolonizethewatercolumnof theponds whentheyrefloodovertheyears,influencing futurehabitatconditionsandzooplanktoncommunitystructureviapriorityeffects(HAVEL& SHURIN2004). Weaimtotestthishypothesisinthefollowingyears.

Althoughour resultssuggest ahighdispersalcapacityfor cyclopoids,thismaybe scaledependent.Our resultsandthoseof previousstudies(JENKINSBUIKEMA1998, CÁCERESSOLUK2002) mightbeexplainedby highdispersalcapacityfor cyclopoidsover shorterdistancesof <10km.However, itremainspossiblethatcladoceranshaveagreater capacitytobedispersedoverlongdistancesof >100kmor >1000kmby waterfowl,as suggestedby DEJENetal.(2004), e.g.becausetheirrestingeggscansurvivefor longperiods inabird’s gut.Bearingin mindthelackofpreviousinformationaboutcopepoddispersal comparedwithothergroups such as cladoceransandanostracans(seeBILTONetal.2001, BOHONAKJENKINS2003 for reviews),our resultshighlighttheneedfor furtherresearch intothedispersalmechanismsandpopulationand molecularecologyof copepods.

Acknowledgments

Thiswork was financedby theSpanishMinisteriodeMedioAmbienteDoñana2005 restorationprojectandviaapostdoctoralfellowshipfromtheMinisteriodeEducacióny CienciatoDF. WearegratefultoARANTZAARECHEDERRA for herassistancewiththe hatchingexperiment,toRICARDODÍAZ-DELGADOfor helpingwiththepreparationof Fig.1, andtoLUISSANTAMARÍAfor usefuldiscussions.

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Table1. Pond detailsandvolumeof watersamplescollectedinsevennew temporaryponds (Caracolesestate,DoñanaNationalPark). “Size”isanestimationof thepond basinareathat was coveredwithwateron thesampledateand“Depth”representsmaximumwaterdepth measuredintherespectiveponds.

Table2. Means andrangesof zooplanktonindividualshatchingfromsedimentsamplesof the topsedimentlayer(0-4 cm)of thereferencesitesLuciodeMarilópezandLuciodelLobo.

Thesamplesurfaceof eachcorewas 50.3 cm2.Themeannumberof hatchlingswas

calculatedper m2.

Lobo

Table3. Density(Ind/L)of copepods(Metacyclops minutus,Megacyclops viridis), cladocerans(Moina brachiata) andmonogonontrotifers(Brachionus variabilis, andan unidentifiedspecies)insevennew temporaryponds (Caracolesestate).Ostracods werenot recordedintheponds. For copepods,developmentalstagesaregivenas follows:calanoid (cal)andcyclopoid(cyc)nauplii,cyclopoidcopepodidsC1toC4,cyclopoidcopepodid5

(C5) andadults.Calanoidcopepodsolderthanthenaupliistageandjuvenilecladoceranswere notpresentintheponds studied.

PondCalCycCycM. minutusM. viridisMoina brachiata Rotifers

Table4. Crustaceanspeciesrecordedintemporarywaterbodiesof theCaracolesestateduring the2003-2004 winter(FRISCHetal.2006, FRISCHetal.unpubl.).Ostracods wererecorded, but notidentified.

Branchiopoda

Cladocera

Alona rectangula (Sars,1862) Daphnia magna (Straus,1820) Daphnia pulex (Leydig,1860) Dunhevediacrassa (King, 1853) Moina brachiata (Jurine,1820) Moina salina (Daday,1888)

Anostraca

Chirocephalus diaphanus Prevost 1803

Notostraca

Triops cancriformis Bosc 1801

Copepoda

Calanoida

Arctodiaptomus wierzejskii(Richard)1888

Copidodiaptomus numidicus (Gurney) 1909

Cyclopoida

Diacyclopsbisetosus (Rehberg)1880

Metacyclops minutus (Claus)1863

Harpacticoida

Cletocamptus retrogressus Shmankevich1875

Table5. CalculationofM. minutuspopulationgrowth, assuming1fertilizedfemalefounded thepopulationon day1 andindividualfecundityof 30 eggs perday(MAIER1995). Developmenttimeswereassumedat1 dayfromeggtonauplii,5 days for naupliar developmentand2 days for copepodiddevelopment,basedon datareportedfor 20ºC by MAIER(1992). Mortalitiesfromeggstoadultswas setat60%, of which40% wereestimated tooccurinthenaupliarphaseand20 % inthecopepodidphase,exceedingexperimentaldata availableforothercopepods,whichestimatetotaljuvenilemortalityat40 to50% (FRISCH

2001, SARVALA1979, ELBOURN1966). Adultmortalitywas neglectedbecausepresumably thetemporaryponds werepredator-freeandthelifespan of adultcyclopoidscanexceed20

days (HOPPetal.1997).

21 619 18570 30750 1440

Table6. Estimatednumberof Metacyclops minutus naupliiandrequiredcolonistsperpond. For anapproximationof nauplii/pondwe multipliedInd/Lby estimatedpond volume(water surfacearea*maximumdepth/2).Numberof colonistswerebasedon thenumberof nauplii (19050 Ind) inamodelpopulationon day20afteritsfoundationon day1 (Table5).

2N1

DoñanaNationalPark

L

ML

8N3

0N3

CaracolesEstate

9S1

10S2

2S2

0S2

N5S4

8S3

4S4

5S3

6S30S3

01000m

Fig.1:Studyarea,showingtheoutlineof DoñanaNationalPark andthelocationof thetwo referencesitessampledfor sediment(L=LuciodelLobo,ML=LuciodeMarilópez).The mapdetailshows theareaof thenewlyconstructedponds, of whichdifferentdiametersare indicatedby dotsizes.Labelsindicatetheponds sampledforthepresentstudy(whitelabels: water,greylabels:sediment).

Fig.2:Photographof thepond 8S3, withtheoutlineof thedesignatedpond basin(dotted whiteline)on 17 March2005. As withtheothersampledponds, onlypartof thedesignated pond basinwas coveredwithwater.In 8S3, athirdof thesurfacewas floodedatamaximum waterdepthof 5 cm(seeTable1).

80

Lobo

60Marilópez

40

20

0

0-44-88-1212-16

Sedimentdepth(cm)

Fig.3:Verticaldistributionofzooplanktonhatchingwithinaweekfromsedimentcoresof the referencesitesMarilópez(ML) andLobo.Thegraphshows mean(columns)andSD (bars)

for 6 replicatesamplesof four depthsineachreferencesite.