Assessing natural resources in the Noosa Biosphere to ......water quality (Gillies et al., 2018; Grabowski et al., 2012). The importance of reefs to estuaries has underpinned the recognition

AssessingnaturalresourcesintheNoosaBiospheretorestoreafunctionalestuary:

interimreport

Reportpreparedby:

DrCarmelMcDougall

AustralianRiversInstitute,GriffithUniversity,Brisbane

DrSimonWalkerEcologicalServiceProfessionalsPtyLtd,Brisbane

For:

TheNoosaBiosphereReserveFoundation

EcologicalServiceProfessionalsPtyLtd

October2020

AustralianRiversInstitute Page|1 InterimReport

Authorcontactdetails'0449218134

*[email protected]

8https://www.griffith.edu.au/australian-rivers-institute

ReportcitationMcDougallC,WalkerS,2020.AssessingnaturalresourcesintheNoosaBiospheretorestoreafunctionalestuary;interimreport.AustralianRiversInstitute,GriffithUniversity,Brisbane


Contents1. ExecutiveSummary........................................................................................................42. ProjectBackground........................................................................................................53. Methods.........................................................................................................................7

Ambientwaterquality.............................................................................................7Aim1-EvaluatethedistributionanddiversityofoysterspecieswithintheNoosaestuary.....................................................................................................................7Aim2-Evaluatethesettlementpreferencesofdetectedoysterspecies...............9Aim3-InvestigatetheutilityofeDNAfordetectionandmonitoringofoysterbiodiversity.............................................................................................................10

4. ResultsandDiscussion.................................................................................................10Characterisationofcollectionsites........................................................................10ThedistributionanddiversityofoysterspecieswithintheNoosaestuary...........11SettlementpreferencesofoysterspeciesintheNoosaestuary...........................14Comparisonofmethodsforspeciesdetection......................................................18Historicalsignificanceandimplicationsforshellfishdesign..................................18

5. Acknowledgements.....................................................................................................196. References...................................................................................................................20

Figures

Figure1. Intertidalremnantoysterreef,TurkeyBeach,Queensland.............................5Figure2. SitesinthelowerNoosaEstuary.Bluedots:adultoystercollectionsite.Black

dots:settlementrackdeploymentsite.Pinkdots:eDNAsamplecollectionsite...........................................................................................................................8

Figure3. Settlementplaterackdesign.Top:constructionofsettlementracks.Bottom:settlementrackinsituatsiteSD1....................................................................9

Figure4. MorphologyofadultSaccostreaglomerataandSaccostrealineageG..........12Figure5. SubtidalrockrubbleandoysterbankatTewantin.........................................13Figure6. LowreliefaggregationofsubtidalleafoysterbedoversandandmudinWeyba

Creek...............................................................................................................13Figure7. Morphologyofspatofeachdetectedspecies................................................15Figure8. Averageabundance(±SE)ofrockoystersonhorizontalsettlementplates

amongsites.....................................................................................................16Figure9. Averageabundance(±SE)ofrockoystersonverticalsettlementplatesamong

sites.................................................................................................................16Figure10. Settlmentplateswithhighcoverageofsedimentonuppersurface..............17


TablesTable1 Waterqualityparametersmeasuredinsituateachsite...............................11Table2 Temperatureandsalinityforoptimumgrowthandtolerancelimitfor

Saccostreaglomerata.....................................................................................13Table3 PERMANOVAresultsfordifferencesinoysterdensityamongsite,substrate

typesandsurfaceorientations........................................................................17


1. ExecutiveSummary

Shellfishreefsareculturally,economically,andecologicallyimportantbuthavealmostentirelydisappearedfromAustralia’scoastlines.IntheNoosaestuary,oysterswereonceabundantbuthavenotrecoveredsinceoverharvestinginthelate19thcentury.Oysterreefrestorationprojectshavecommencedbuttheirefficacytorestorethislosthabitattypeisunknown.Thisprojectaimsto1)evaluatethedistributionanddiversityofoysterspecieswithintheestuary,2)evaluateoystersettlementpreferences,and3)investigateenvironmentalDNAtechniquesfordetectionandmonitoringofrestoredreefs.Thiswilldirectlyinformthedesignofreefmodulestomaximisesettlementofoysterspeciesforongoingrestorationprojets.

Thesudyfindsthat:

1. Minimally, there are four species of rock oyster present in the estuary. These includeSaccostreaglomerata(theSydneyrockoyster),SaccostrealineageB,SaccostrealineageG,andOstreaequestris.

2. Theoysters(andtheirspat)cannotbereliablyidentifiedbymorphologyalone.3. Ostreaequestriswasonlydetectedonsettlementplates,whereasSaccostrea lineageB

wasonlydetectedviasurvey.4. Oyster diversity appears to be higher near the rivermouth than in the upper reaches,

withSaccostreaglomerata thesolespeciespresentupstream.This result ispreliminaryandneedstobeverifiedwithsequencingofadditionalspecimens.

5. Several other native shellfish were identified in the estuary, including pearl oysters(Pinctadaalbina/nigraspeciescomplex),hairymussel(Trichomyahirsuta)andleafoyster(Isognomon ephippium, identified by morphology only) that are capable of clumping,consolidatingrubble/shellsubstrateandcontributingtothediversityofrestoredshellfishreefhabitats.

Eachrockoysterspeciesrecorded,oracombination,couldbetargetedforshellfishreefrestoration,however,consideringthemoderndaydominanceofS.glomerataitisanobviouschoice.ThecurrentdistributionofS.glomerataintheNoosaestuaryappearstobelargelylimitedtotheintertidalzone,withonlysparseindividualsobservedsubtidally(likelyaresultofcomplexecologicalinteractionsbetweenenvironmentalconditions,predation,settlementandrecruitmentandotherdisturbance).Thisstudyidentifiedkeyshellfishspeciesinatropical/sub-tropicalsetting,whichwillinformthefuturedesignphaseofrestorationefforts,includinghabitatsuitabilitymodelsandotheraspectsoftheearlydesignofhabitats.Thisisexpectedtoresultinsignificantcostsavingsbyhelpingimprovetheefficiencyandefficacyofcurrentandfuturerestorationeffortsaimedatrevivingtheselostorthreatenedecosystems.Thisstudyalsoprovidesanexcellentopportunitytotrialinnovative‘environmentalDNA’(eDNA)techniquesforthedetectionofoysterspeciesthroughouttheestuary.eDNA(DNAshedbyorganismsintotheenvironment)canbeobtainedfromwater(orsoil)samples,andcanallowdetectionoforganismswithoutneedingtosurveylargenumbersof(potentiallypoorlyaccessible)sites.ThisprojectwillprovidethefirstcomparisonofoysterbiodiversityobtainedfromeDNAsamplingcomparedwithtraditionalphysicalsurveysthroughouttheestuary.Ifsuccessful,wewilldevelopanefficientmeansofevaluatingoysterpopulations,whichcanbeappliedintheNoosaRiverestuaryandtootherestuariesaroundtheworld.Theresultsfromthisaspectoftheprojectwillbepresentedinthefinalreport.


2. ProjectBackground

Shellfishreefs(reefscomposedpredominatelyofbivalvemolluscs)arenotasfamous,orperhapsasbeautiful,ascoralreefs,butwereoncecommonalongAustralia’scoastline(Gilliesetal.,2018)(Figure1).Thesereefsprovideimportantecosystemfunctionsincludingcoastlineprotection,habitatprovision,carbonsequestration,foodprovision,andimprovementofwaterquality(Gilliesetal.,2018;Grabowskietal.,2012).TheimportanceofreefstoestuarieshasunderpinnedtherecognitionofshellfishreefsasawetlandhabitattypeaspartoftheConventiononWetlandsofInternationalImportance(TheRamsarConvention–habitattype‘Ga’)(Kasoaretal.,2015).Todayoysterreefsareconsideredgloballythreatened,withanestimated85percentofhistoricalreeflost(includingfromAustralia)(Becketal.,2011;Gilliesetal.,2018).Thefunctionallossofoysterreefhabitatshasbeenlinkedtooveralldeclinesinecosystemproductivity,particularlyoffishstocks,likelyduetothelossofforagingandnurseryhabitats(Gilbyetal.,2018).Thelossofshellfishreefshasbeenattributedtoseveralfactorsincludingoverexploitation,dredging,increasedsedimentation,disease,andfloodevents(Becketal.,2011).Thepersistenceofmanyofthesestressorsmaymeanthatthesereefscannotberestored(Gilbyetal.,2018).However,examplesofsuccessfulshellfishreefrestorationprojectsintheUnitedStates,andtheconfirmationofoystersurvivalandrecruitmentonvariousprojectswithinAustralia,includingwithintheNoosaRiverestuaryindicatethat,withsuitablereefrestorationdesign,ongoingmonitoringandmaintenance,manyoftheseecosystemsmaybeabletoberecovered.

Figure1. Intertidalremnantoysterreef,TurkeyBeach,Queensland


IntheUSA,oysterrestorationisleadingthewayinestuarinerestorationthroughthecreationof“green”jobsfollowingtheUSeconomicdownturn(Edwardsetal.,2013).Theserestorationprojectsprovidesubstantiallocalemploymentandeconomicopportunitiesthroughthecreationofnaturalinfrastructurethatcanenhanceecosystemservices(includingcoastalprotection)worthmillionsofdollarsandsupportotherindustriesincludingfishing(boostingcommercialandrecreationalproductivity)andtourism(Grabowskietal.,2012;Petersonetal.,2003).DespiteevidenceofsubstantialdeclinesintheconditionofestuariesinAustraliaandcallstorestorethemtomaintainfisheriesproductivity(Gilliesetal.,2018),marinerestorationinAustraliahastypicallylaggedbehindtherestoftheworld.However,shellfishreefrestorationprojectsarerecentlygainingmomentumwithinAustralia,withseverallarge-scaleprojectsinvestingupwardsof$20milliontowardsrestorationefforts.TherearecurrentlyseveralinitiativeswithinAustraliathataimtoprovidescience-based,well-consideredrestorationofhabitatsthathavebeenlost,includingtherestorationofoysterreefs(www.shellfishrestoration.org.au).TwoprojectsarecurrentlyunderwayinQueensland;oneinPumicestonePassage(MoretonBay),andanotherintheNoosaRiverestuary.

ResearchintothehistoryoftheNoosaRiverestuaryhasrevealedextensiveIndigenoususeofoysters(evidencedbylargeshellmiddensandreferencesfromearlysettlers),andtheexistenceofalargeoysterfisheryinthelate19thandearly20thcenturies(Thurston,2015).Leasesweregrantedfrom1881onward,andoysterswereharvested,includingbydredge,formarketsinBrisbaneandbeyond(Thurston,2015).Evenafterlargeoystershadallbutdisappeared,harvestofyoungoystersalsooccurredbydredge,theseweretransportedliveandon-growninMoretonBay(Thurston,2015).By1930commercialoysterharvestingintheNoosaestuaryhadlargelyceased,yetpopulationshavestillnotrecovered(Thurston,2015).Itisthoughtthatthedredgingofoysterbanksremovedalargeproportionofthesubstraterequiredforoystersettlement,andthatthehumanmodificationsoftheestuary(particularlytheNoosaRivermouth)furtherreducedtheavailabilityandsuitabilityofhabitat(Thurston,2015).

ItisgenerallyassumedthattheoysterspeciesharvestedfromtheNoosaestuarywastheSydneyRockoyster,howeverhistoricalrecordspointtowardsmorphologicaldifferencesbetween‘dredge’and‘bank’shellfish(Saville-Kent,1891).ArecentsurveyofoysterspeciesaroundtheQueenslandcoasthasrevealedhigherthanexpecteddiversity,withanumberofcurrentlyunrecognisedspeciescommonlyfoundinsimilarhabitatstoSydneyRockoysters(McDougalletal.,2020).Itisthereforepossiblethatdredgeandbankoystersrepresentdistinctspecies;thiswouldhaveimportantimplicationsforshellfishreefrestorationprojectsandmayexplainwhysettlementhasnotbeenobservedonsubmergedsubstratesinareaswithhealthySydneyRockoysterpopulationsinsometrialswithintheNoosaestuary(Gilby,2018;TheNatureConservancyandEcologicalServiceProfessionals,2015).

InNoosa,anoysterrestorationprogramisunderwaytorestorerockoysterreefsthatwerethoughttohaveconsistedofSydneyrockoysters.Unexpectedly,earlyresultshaveindicatedthatseveraltypesofoysteraresettling–theidentityofthese‘other’oystersisunknown,andlikelyreflectsthepaucityofinformationregardingoysterbiodiversity,ratherthantherecruitmentofexoticspecies.Thesignificantlackofknowledgeofshellfishreefecosystems


hasbeenhighlightedintheliteratureasapriorityforresearch,andpriorstudieshaveoftenoversimplifiedshellfishreefecosystems(Gilliesetal.,2018);manymoreoysterspeciesarecapableofformingreefs,andreefsareoftencomposedofmultipleshellfishspecies(McDougall,unpublisheddata).Interspecificdifferencesinbiologyandhabitatpreferencesmeanthatsomeoysterspeciesarelikelytobemoresuitableforreefrestorationprojectsthanothers,butthisknowledgeiscriticallylacking.Understandingwhichspeciesarebeingtargetedinreefrestorationprojectsisessentialforoptimaldesign,whichshouldtakeintoaccountthehabitatpreferencesofthespeciesnaturally(and/orhistorically)foundinthearea.Furthermore,increasingdiversityofecosystemscanimprovetheircapacitytorespondto,andrecoverfrom,futuredisturbances.

Understandingoftheecologyoftargetspeciesisanessentialcomponentforsuccessfulrestorationprojects,howeverduetotaxonomiccomplexitiesinthisimportantshellfishgroup,ithasbecomeevidentthatageneticscreenisnecessarytodeterminethewealthofshellfishdiversity.Thisinformationwouldinformdesignoflarge-scalerestorationinitiatives,andaddressesanimportantknowledgegapidentifiedduringthetrialreefrestorationphaseinNoosa.Therefore,theaimsofthisprojectwereto:

1. EvaluatethedistributionanddiversityofoysterspecieswithintheNoosaestuary.2. Evaluatethesettlementpreferencesofdetectedoysterspecies.3. InvestigatetheutilityofeDNAfordetectionandmonitoringofoysterbiodiversityinthe

estuary.

3. Methods

Ambientwaterquality

Waterqualityparametersweremeasuredinsurfacewaters(30cmbelowthesurface)ateachsiteonseveraldaysduringdeploymentofsettlementplatesandwhilecollectingeDNAsamples.WaterqualitywasloggedusingaYSIProDSSmulti-parameterwaterqualitysonde.TheunitwascalibratedpriortodeploymentmanufacturercalibrationmethodsandsamplingcompletedinaccordancewiththeQueenslandMonitoringandSamplingManual2018(DepartmentofEnvironmentandScience,2018)forthefollowingparameters:watertemperature;dissolvedOxygen;specificconductance;salinity;pH;and,turbidity.

Aim1-EvaluatethedistributionanddiversityofoysterspecieswithintheNoosaestuary.

SamplingofoystersintheNoosaEstuarywasconductedbyfootonthe18thofDecember2019andbyboatonthe24thofAugust2020.Eightcollectionsiteswereselectedbasedontheavailabilityofhardsubstrateandthepresenceofoysters(Figure2).Waterqualityparameterswererecordedateachsite.Betweenthreeandtwelvespecimenswerecollectedateachsitedependingontheobservedmorphologicaldiversityapparentinthepopulation.Oysterswerestoredincoolerboxesoniceandreturnedtothelaboratory,wheresampleswerestoredin70%ethanoluntilprocessed.NoadultoysterswereobservedonmangroverootsatsiteSD1althoughoystersdidsettleonexperimentalsettlementplates.


Figure2. SitesinthelowerNoosaEstuary.Bluedots:adultoystercollectionsite.Blackdots:settlementrackdeploymentsite.Pinkdots:eDNAsamplecollectionsite.

Oysterswerephotographed,shucked,andasmallsampleofadductormusclewasdissected.ExtractionswereperformedusingtheDNeasyBloodandTissueDNAKit(Qiagen)asperthe

¬«A6

¬«A5

¬«A4

¬«A3

¬«A1

¬«A2

¬«E1

¬«A7¬«E2

¬«E3

¬«A8

¬«S13

¬«S12¬«SD1

Oyster Survey Sites

±0 0.5 1 1.5 20.25Kilometers

Datum: GDA2020 Zone 56JData Sources:© State of Queensland.All care has been taken to ensure the accuracy of data. However,Griffith University make no representations or warranties about the accuracy, reliability or suitability and disclaims all liability for expenses, damages and costs incurred due to the data being incomplete or inaccurate.

LegendSurvey Sites

Adult Oyster Collection

Settlement Plates

eDNA

Noosa Heads


manufacturer’sinstructions.Apartialfragmentofthe16SgenewasamplifiedbyPCRusingthetheprimers16S_Fwd(Banksetal.,1993)and16Sbr-H(Palumbietal.,1991)andthefollowingthermoprofile:95°Cfor30seconds,followedby30cyclesof95°Cfor1minute,51°Cfor1minuteand68°Cfor1minute,andafinalextensionat68°Cfor5minutes.PCRproductsweregelpurifiedandsenttoMacrogen(SouthKorea)forsequencing.Resultingtraceswerequalitytrimmed.Speciesidentificationwasperformedbyaligningtheresultingsequencesagainstanin-housedatabaseofoyster16Ssequences.

Aim2-Evaluatethesettlementpreferencesofdetectedoysterspecies.

Settlementracksweredeployedatthreesitesonthe18thofDecember2019(Figure2).Rackscontainedpairedstackedplates(onenylon,oneconcrete),withfourpairsplacedhorizontallyonthetopoftheunit,andfourpositionedverticallyattheendoftheposts(Figure3).Treatedshells(bothSROandPacific)werecable-tiedontoeachoftheposts(4ofeachspeciesoneachrack).UnitsweredeployedattwoexistingrestorationsitesandonenewsiteinLakeDoonella,andwerepositionedinordertobeexposedduringlowtide.Waterqualityparameterswererecordedateachsite.

Figure3. Settlementplaterackdesign.Top:constructionofsettlementracks.Bottom:settlementrackinsituatsiteSD1.

Settlementplateswerecollectedon8thofMay2020.Theabundanceofattachedspatwasrecorded(basedonmorphology),individualswerephotographed,andtheneachindividualwascarefullyremoved(avoidingcrosscontamination)andpreservedseparatelyin70%


ethanolforsequencing.DNAextractionand16SPCRwasperformedasdescribedabove.Differencesinthedistributionandabundanceofrockoysterswerecomparedamongthetypesofsettlementplates(cementsheetandnylon),surfaceorientations(verticalandhorizontal),andsitesusingathreefactorPERMANOVA.UntransformedoysterabundancewasconvertedtoEuclideandistancematrixpriortoanalysis.Duetosubstantiallossesoftheoystershelltreatmentatsomesites,thesewereexcludedfromformalstatisticalanalyses;however,wheresettlementontooystershelloccurred,theresultsforcomparisonwiththeothertreatments.

Aim3-InvestigatetheutilityofeDNAfordetectionandmonitoringofoysterbiodiversity.

Watersamples(2Lwatersample,fourreplicatespersite)weretakenintosterileplasticcontainersatthreesitesvisitedonthe24thofAugust,2020(Figure2),fromsiteE1atslacklowtide,siteE3onanincomingtide,andsiteE2atslackhightide.Samplesweretakenfromthemiddleofthechannelandapproximately10cmbelowthesurface.Watersampleswerekeptoniceinthefieldandat4°Cuponreturntothelaboratory,andwerefilteredthroughsterile250mL0.45µmcellulosenitratefilterfunnels(Nalgene145-2045)usingavacuummanifold.Filtrationwascompletedwithin24hoursofsamplecollection.Threeadditionalsterileplasticcontainerswerefiledwithwaterfromthelaboratorysink(waterthebottleshadbeenrinsedin)andfilteredtoprovidenegativecontrols.DNAextractionwasperformedusingtheDNeasyBloodandTissuekit(Qiagen)protocol,withamodifiedlysisstepasperformedbyAlexanderetal.,2019.

4. ResultsandDiscussion

Characterisationofcollectionsites

CollectionsitesspannedfromtheNoosaRivermouthupstreamtotheentrancetoLakeCooroibah,andincludedsitesinLakeDoonellaandWeybaCreek(Figure2).Thewaterqualityparametersmeasuredinsituatthevarioussitesweretypicalofthatinlowertomid-estuarinewaters,withtemerpaturereflectingtheambientairtemperature,gooddissolvedoxygenconcentrationandpHtypicalofseawater(Table1).Turbidityrangedfrom1to39NTU,withthehighestrecordsoccurringinLakeDoonella(siteSD1).Theexceptionwassalinity(andspecificconductance),whichtypicallyrangedfrom23to42PSU.ThehighestrecordsoccurredatsitesinWeybaCreek(sitesS12&S13)inDecember2019(Table1),followinganextremelydryperiodwithverylowrainfall.Thesehypersalineconditionsexceededthenormalgrowingconditions;however,salinitymeasuredinMarch2020followingrainfallhaddeclinedtoexpectedsalinitylevels,andwellwithintheoptimalgrowthrangeforrockoysters(Table2).


Table1. Waterqualityparametersmeasuredinsituateachsite

Site Date Time WaterTemperature(°C)

DissolvedOxygen(mg/L)

SpecificConductance(µS/cm)

Salinity(psu)

pH Turbidty(NTU)

SD1 18/12/19 12:36 26.89 6.54 53572 35.33 7.98 9.49 30/4/20 15:15 29.22 8.37 36746 23.14 8.11 39.03 8/5/20 11:00 22.07 6.57 52437 34.59 7.92 12.09A5/S12 18/12/19 11:29 25.53 7.44 61798 41.56 7.87 3.09 30/4/20 Nodata Nodata Nodata Nodata Nodata Nodata Nodata 8/5/20 15:21 23.17 7.49 45396 29.42 8.03 5.64A6/S13 18/12/19 9:45 23.85 7.26 62662 42.26 7.81 8.24 30/4/20 13:00 25.20 6.91 41210 26.38 8.05 4.89 8/5/20 12:35 22.51 7.15 48062 31.36 8.00 3.31A4 24/8/20 9:20 17.83 7.57 49615 32.52 8.22 2.81E1 24/8/20 8:16 18.00 7.22 50393 33.09 8.16 0.99E2 18/12/19 13:00 25.90 6.25 54201 35.82 7.97 6.67 24/8/20 14:06 18.90 7.58 51590 33.98 8.20 1.48A8/E3 24/8/20 12:28 16.61 7.39 46727 30.41 8.05 5.22A1 24/8/20 10:41 19.40 7.50 53330 35.27 8.32 9.64A2 24/8/20 10:04 18.17 7.37 51475 33.89 8.24 1.21A3 24/8/20 8:30 17.50 7.22 49667 32.56 8.18 1.08

ThedistributionanddiversityofoysterspecieswithintheNoosaestuary.

16Sfragmentsweresuccessfullyamplifiedandsequencedfor39oysterscollectedthroughouttheNoosaEstuary.Sequenceanalysisrevealedthattheoystersbelongedtothreedifferentspecies;Saccostreaglomerata(Sydneyrockoyster),SaccostrealineageBandSaccostrealineageG.TheuseofSaccostrea‘lineages’asopposedtospeciesisestablishedintheliteraturebecausethedifficultyinmorphologicallyidentifyingoysterspecieshaspreventedtheconfidentassignmentofspeciesnames(LamandMorton,2006;SekinoandYamashita,2016).Indeed,inthisstudyitwasimpossibletodistinguishSaccostreaglomerataandSaccostrealineageGmorphologically(Figure4).A16Sfragmentwasalsocollectedfora‘hairymussel’collectedfromsiteA2.ThesequenceconfirmsthatthisspeciesisTrichomyahirsuta.

ThefindingofSaccostreaglomerataintheNoosaEstuarywasexpected,andiscongruentwiththeknownnaturaldistributionofthespecies(fromtheTownofSeventeenSeventyinQueenslandtotheBassStrait,andNewZealand).SaccostrealineageBwaspreviouslyreportedfromYepoonandCairns(LamandMorton,2006),andbothSaccostrealineagesBandGwerefoundtobebroadlydistributedinQueenlandinarecentsurvey(McDougalletal.,2020).ThesetwospecieshavebroadIndo-Pacificdistributions,occurringasfarnorthasJapan(SekinoandYamashita,2016).

Saccostreaglomeratawasfoundatallsitessurveyed,otherthansiteSD1atwhichnoadultoysterswerefound.SaccostrealineageGwasfoundatsitesclosetotherivermouthandatTewantinboatramp(sitesA1,A2andA7),butnotinWeybaCreek,LakeDoonella,oratthemouthoflakeCooroibah.SaccostrealineageBwasfoundneartherivermouthonly(siteA1,howeverjuvenilesofthisspecieswereobservedatsiteA2also).Theseresultsindicatethatthethreespecieshavedifferenthabitatrequirements;thismayberelatedtodifferentsalinitytolerancesand/orabilitytowithstandsedimentation.


Figure4. MorphologyofadultSaccostreaglomerataandSaccostrealineageG.

Theaccommodationspacerepresentstheareainanestuarywithenvironmentalconditionssuitableforgrowthofoysters(Volety,2013).Oystersgrowfromtheintertidaltodepthsofatleast20metresandthisiswheremuchofthehandgatheringordredgingofoystershashistoricallyoccurred(Nell,2001).However,itisthoughtthatduetochangesinambientconditionsandavarietyofexternalfactors,rockoystersinSouthernQueenslandaretypicallyfoundonlyintheintertidalzoneandhavebeenfunctionallylostfromsubtidalhabitats(Diggles,2013).ConditionssuitableforoptimalSaccostreaglomeratagrowtharesummarisedbelowfrom(Holliday,1995;NellandHolliday,1988;Rubio,2007).Adultrockoystersareabletoclosetheirvalveforseveraldaysifsalinityislessthan15ppt,althoughprolongedperiodsoflowsalinitycancausedeath(Holliday,1995;NellandHolliday,1988).Basedonambientconditions,itwouldbepossibleforoysterstogrowatanyofthesitessurveyed,wheresuitablesubtsrataisavailableforsettlement(Figure5&6).Optimalconditionsfortheotherbivalvespeciesidentifiedwithinthisstudyarenotpresentlyknown.


Table2. TemperatureandsalinityforoptimumgrowthandtolerancelimitforSaccostreaglomerata

Parameter Units Life History Stage Larvae Spat Adult Temperature optimum growth °C 24-26 14-28 18-26 Temperature tolerance limit °C unknown 11-30 11-30 Salinity optimum growth ppt 23-39 20-40 25-35 Salinity tolerance limit ppt 15-39 0-40 0-50

Figure5. SubtidalrockrubbleandoysterbankatTewantin

Figure6. LowreliefaggregationofsubtidalleafoysterbedoversandandmudinWeybaCreek


SettlementpreferencesofoysterspeciesintheNoosaestuary

DNAfragmentsweresequencefromatotalof44oysterspatcollectedonsettlementracksatthreesitesthroughouttheestuary.Threespeciesweredetected;Saccostreaglomerata,SaccostrealineageG,andOstreaequestris.OstreaequestrishasawidedistributioninbothAtlanticandPacificoceans,includingArgentina,U.S.A.,Japan,ChinaandNewZealand(Huetal.,2019).ThepresenceofthespeciesinAustraliahas,untilnow,notbeenconfirmedwithgeneticevidence(althoughspecimensofthesamespecieswerepreviouslydiscoveredonsettlementplatesinthePumicestonePassage,McDougallunpublisheddata).Itisasubtidalspecies(whichexplainswhyitwasnotfoundintheadultoystersurveys,whichpredominatelyexploredtheintertidalzone),andisreportedtosurviveinhighsalinityenvironments(GaltsoffandMerrill,1962).Twosmallpearloysterspecimenswerealsosequenced;theybothbelongtothePinctadaalbina/nigraspeciescomplex.

Theexternalmorphologyofoysterspatwasrecordedinphotographstakenpriortodissection.Oncesequencingresultshadbeenreturnedphotographswereexaminedtodeterminewhetherspeciescouldbereliablyidentifiedbymorphology.Extensiveoverlappingvariationwasobservedacrossthethreespecies(Figure)indicatingthatmorphologicalidentificationisnotfeasible.

AllthreespeciessettledontoplatesatsitesS12andS13(WeybaCreek),howeveronlySaccostreaglomerataspatweredetectedatsiteSD1(LakeDoonella).Thisisincontrastwithadultoysterdistributions,withonlySaccostreaglomerataadultsdetectedatsitesS12andS13.Thelackorreducedabundanceofotherspecies(specifically,SaccostrealineageG)atthesesitesisnotduetolackoflarvalrecruitment,butmostlikelyduetounfavourableenvironmentalconditionsthatcausemortalityofsettledindividualsenablingthenumericaldominanceofS.glomerata.SpatofSaccostrealineageBwerenotdetectedonanyoftheplates;thiscouldhaveseveralexplanations,forexample,lackoflarvalsupply(adultsofthespecieswereonlydetectedattherivermouth),lackofsuitabilityofplatesforsettlement,earlymortality,orthelackofaspawningevent.Itisnotablethatthe2019/2020summerwasparticularlydry,possiblyaffectingspawningbehaviour.Adultsweregenerallyinlowdensitieswhererecordedatthemouthoftheriver.

Thereweredifferencesinthedensity(individualsper0.01m2)ofoystersonplatesaroundtheestuaryaswellasondifferentsurfaceorientationsandtypesofsettlementsurface(Table:PERMANOVAsitexorientationinteractionpseudo-F2,36=5.55,p=0.002,Figure8&9).Therewasalsoageneralincreaseinthedensityofoysterssettlingontonylonthanconcretesheet(Table:PERMANOVAsubstratetypepseudo-F1,36=4.56,p=0.029,Figure8).Theaveragedensitywasgreatestonhorizontalsurfaces,particularlyontheundersidesofplates.Alayerofsedimenthadaccumulatedontheuppersurfaceofeachplate(Figure,upto5mmthickonsomeplates),whichpreventedsuccessfulattachment.ThegreatestdensityofoysterswasrecordedatsiteS12,whichisclosesttothemouthofWeybaCreek.Onverticalsurfaces,thedensityofrecentlysettledoysterspatontooystershellswastypicallysimilartothatfoundonverticalnylonsheetsatsiteS12,butmuchgreaterthanonoystershellthanontheplatesatsiteS13(Figure).


Figure7. Morphologyofspatofeachdetectedspecies.


Figure8. Averageabundance(±SE)ofrockoystersonhorizontalsettlementplatesamongsites

Figure9. Averageabundance(±SE)ofrockoystersonverticalsettlementplatesamongsites

0.0

10.0

20.0

30.0

40.0

50.0

60.0

DS1 S12 S13

Mea

n ab

unda

nce

(ind.

/0.0

1m2

)(±SE

)

Site

Concrete sheet Nylon

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

DS1 S12 S13

Mea

n ab

unda

nce

(ind.

/0.0

1m2

)(±SE

)

Site

Concrete sheet Nylon Oyster shell


Table3. PERMANOVAresultsfordifferencesinoysterdensityamongsite,substratetypesandsurfaceorientations.

Factor df MS Pseudo-F P(perm)Site 2 1654 20.16 0.001

SubstrateType 1 374 4.56 0.029Orientation 1 884 10.77 0.002

SitexSubstrateType 2 221 2.69 0.081SitexOrientation 2 455 5.55 0.002

SubstrateTypexOrientation 1 96 1.17 0.302

SitexSubstrateTypexOrientation 2 28 0.34 0.743Error 36 82

PariwiseComparisons (b)HorizontalvsVertical

t-value P(perm)

S12 2.68 0.010 S13 4.11 0.002

DS1 4.43 0.001 (c)Horizontal (d)Vertical

Differencesbetweensites t-value P(perm) t-value P(perm)S12vsS13 3.53 0.005 3.12 0.004

S12vsDS1 3.76 0.003 3.22 0.003

S13vsDS1 2.10 0.061 0.68 0.586

Figure10. SettlmentplateswithhighcoverageofsedimentonuppersurfaceinMay2020


Comparisonofmethodsforspeciesdetection

Neitherofthetwomethodsofspeciesdetectioninvestigatedsofar(adultoystersurveysorsettlementplates)gaveacomprehensivepictureofthespeciespresentwithintheNoosaestuary.Itispossiblethatadditionalspeciesremaintobedetected,particularlythosethatoccursubtidally.Oystersurveyswouldpossiblyhavebeenmorecompletehadsubtidalcollectiontechniquesbeenutilised,andadditionalspeciesmayhavebeencollectedonsettlementplatesiftheyhadbeendeployedatadditionalsites.Eachofthesemodificationpresentsadditionallogisticalchallenges;useofdiversforcollectionisexpensive(anddredgeshit-and-miss),andsettlementplatesdeployedatlocationswithhigherhumantraffic(suchasaroundtherivermouth)aremorelikelytobeinterferedwith.WeawaittheresultsoftheeDNAsamplingtoseeifthisprovidesamorerobustwaytodetecttherangeofspeciespresent(includingamixofbothadultsandspat).Untilthen,itappearsthatusingacombinationoftechniquesisneededtodetermineaccuratelythecompositionofoysterassemblagesinestuaries,andinparticularontohabitatrestorationunits.

Historicalsignificanceandimplicationsforshellfishdesign

ThehistoricalpresenceofoystersintheNoosaestuaryiswellrecorded,bothwithinmiddensandintheliterature(Thurston,2015).Whilenomentionismadeofthespeciesofoysterpresent,‘bank’and‘dredge’oystersaredistinguished.Saville-Kent(1891)believedthattheserepresentedtwoformsofSaccostreaglomerata,andnotedthatthedifferenceinmorphologywaslikelyanenvironmentaleffect,withsubtidal‘dredge’oystershaving‘asmootherandmoreponderousform,withoftenanabnormallyelongatedcontour,andamoreorlesscompleteabsenceoftheconspicuouscolourationcharacteristicoftheshellsexposedtolightandair’.Despitethis,healsonotedthatthetwo‘forms’ofoystersoccurredwithinthesameclump,leavingopenthepossibilitythattheyaredistinctspecies.Inadditiontothesereports,anewspaperarticlefrom1915authoredbyHarryC.Perrystatesthat‘MudoystersareplentifulinLakeWeyba’(Perry,1915).While‘mudoysters’insouthernstatesrefertoOstreaangasi,thespeciesdoesnotoccurinQueensland.Otherarticlesindicatethattheterm‘mudoyster’wasusedforanyoysteroccurringbelowthelowwatermark(1934).Giventhedifficultyindistinguishingoysterspeciesbymorphology,determiningwhatspecieswerehistoricallypresentintheNoosaestuarywillbechallenging,particularlyiflivingspecimenshavebecomelocallyextinctandarcheologicalevidencefrommiddensneedstobereliedupon.Saccostreaglomerata,SaccostrealineageGandSaccostrealineageBaremorphologicallyverysimilarasadults,andwerelikelyconsideredtheonespeciesinhistoricalaccounts.Whetheraccuratedeterminationscanbemadefrommiddenspecimensremainstobeestablished.

ThisstudyhasshownthatthereareatleastfourspeciesofrockoysterpresentintheNoosaestuary,presumablyeachofthese,oracombination,couldbetargetedforshellfishreefrestoration.Giventhateachspecieslikelyhasuniqueenvironmentalrequirements,andthatmodellingforappropriatereefrestorationsitesisgenerallybasedonparametersforSaccostreaglomerata,considerationofalternativespeciesmaysignificantlyincreasethenumberofpossiblesites.Thedetectionofasubtidalspecies,Ostreaequestris,suggeststhat


submergedreefsmaybepossible;however,reportsindicatethatthespeciesdoesnotnaturallyformreefs(GaltsoffandMerrill,1962).Giventheresultspresentedhere,werecommendtrialstoexploretheattributesofeachspecies(resilience,performance,provisionofecosystemservices)underdifferentenvironmentalconditionstoprovideessentialbaselineinformationtointegratewithshellfishreefrestorationdesigns.

5. AcknowledgementsTheauthorswouldliketoacknowledgetheprojectfunders,GriffithUniversityandtheNoosaBiosphereReserveFoundation,NikolinaNenadic for laboratoryassistance,andBryanWalshfromtheNoosaParksAssociationforfieldassistance.


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Documents

Assessing natural resources in the Noosa Biosphere to ......water quality (Gillies et al., 2018; Grabowski et al., 2012). The importance of reefs to estuaries has underpinned the recognition