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1 California Sea Grant College Program UC San Diego Peer Reviewed Title: Effects of competition and dispersal on the recruitment of the annual kelp Nereocystis luetkeana Author: Suskiewicz, Matthew S., San José State University/Department of Marine Science Publication Date: Series: Research Theses and Dissertations Publication Info: Research Theses and Dissertations, California Sea Grant College Program, UC San Diego Permalink: Additional Info: Thesis submitted by Matthew S. Suskiewicz August 2010 and approved for the Department of Marine Science, San José State University. Keywords: abalone, kelp, farming, seaweed, algae, Macrosystis, Nereocystis luetkeana, diet Abstract: In central California, the role of algal assemblages on the recruitment of the canopy producing annual kelp Nereocystis luetkeana was examined by experimentally manipulating canopy and understory algae within 1) a Macrocysits bed and 2) a Nereocystis bed. Nereocystis reproductive material was introduced in some plots to examine the role of dispersal distance on recruitment. Nereocystis recruitment at both sites was significantly higher during spring compared to recruitment observed later in the study. Recruitment continued throughout the fall, however, suggesting a broad recruitment window. Recruitment success increased dramatically when understory algae were removed. Presence of a canopy (Nereocystis or Macrocystis) did not affect Nereocystis recruitment, suggesting that Nereocystis was not directly competitively inferior to Macrocystis. Greater recruitment was observed in areas seeded with Nereocystis propagules. Ultimately, recruitment of Nereocystis was controlled by understory algal assemblages and by the relatively short dispersal distance of its propagules. Additionally, the broad recruitment window for Nereocystis described here suggests that summer recruits can contribute to population resilience to late spring disturbances. This study indicates that given sufficient disturbance to the benthos and ample propagule supply, Nereocystis should be able to recruit and colonize new areas, regardless of the presence of Macrocystis. escholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.

2 San Jose State University SJSU ScholarWorks Master's Theses Master's Theses and Graduate Research 2010 EFFECTS OF COMPETITION AND DISPERSAL ON THE RECRUITMENT OF THE ANNUAL KELP NEREOCYSTIS LUETKEANA Matthew Suskiewicz San Jose State University, Recommended Citation Suskiewicz, Matthew, "EFFECTS OF COMPETITION AND DISPERSAL ON THE RECRUITMENT OF THE ANNUAL KELP NEREOCYSTIS LUETKEANA" (2010). Master's Theses. Paper This Thesis is brought to you for free and open access by the Master's Theses and Graduate Research at SJSU ScholarWorks. It has been accepted for inclusion in Master's Theses by an authorized administrator of SJSU ScholarWorks. For more information, please contact

3 EFFECTSOFCOMPETITIONANDDISPERSALONTHERECRUITMENT OFTHEANNUALKELPNEREOCYSTISLUETKEANA AThesis Presentedto TheFacultyoftheDepartmentofMarineScience MossLandingMarineLaboratories SanJoséStateUniversity InPartialFulfillment oftherequirementsforthedegree MasterofScience by MatthewS.Suskiewicz August2010

4 2010 MatthewSuskiewicz ALLRIGHTSRESERVED

5 TheDesignatedThesisCommitteeApprovestheThesisTitled EFFECTSOFCOMPETITIONANDDISPERSALONTHERECRUITMENTOFTHE ANNUALKELPNEREOCYSTISLUETKEANA by MatthewS.Suskiewicz APPROVEDFORTHEDEPARTMENTOFMARINESCIENCE SANJOSÉSTATEUNIVERSITY August2010 Dr.MichaelH.Graham, Dr.IvanoW.Aiello, DepartmentofMarineScience DepartmentofMarineScience Dr.JamesA.Estes, UniversityofCaliforniaatSantaCruz

6 ABSTRACT EFFECTSOFCOMPETITIONANDDISPERSALONTHERECRUITMENTOFTHE ANNUALKELPNEREOCYSTISLUETKEANA ByMatthewSuskiewicz IncentralCalifornia,theroleofalgalassemblagesontherecruitmentofthe canopyproducingannualkelpnereocystisluetkeanawasexaminedby experimentallymanipulatingcanopyandunderstoryalgaewithin1)amacrocysits bedand2)anereocystisbed.nereocystisreproductivematerialwasintroducedin someplotstoexaminetheroleofdispersaldistanceonrecruitment.nereocystis recruitmentatbothsiteswassignificantlyhigherduringspringcomparedto recruitmentobservedlaterinthestudy.recruitmentcontinuedthroughoutthefall, however,suggestingabroadrecruitmentwindow.recruitmentsuccessincreased dramaticallywhenunderstoryalgaewereremoved.presenceofacanopy (NereocystisorMacrocystis)didnotaffectNereocystisrecruitment,suggestingthat NereocystiswasnotdirectlycompetitivelyinferiortoMacrocystis.Greater recruitmentwasobservedinareasseededwithnereocystispropagules.ultimately, recruitmentofnereocystiswascontrolledbyunderstoryalgalassemblagesandby therelativelyshortdispersaldistanceofitspropagules.additionally,thebroad recruitmentwindowfornereocystisdescribedheresuggeststhatsummerrecruits cancontributetopopulationresiliencetolatespringdisturbances.thisstudy indicatesthatgivensufficientdisturbancetothebenthosandamplepropagule supply,nereocystisshouldbeabletorecruitandcolonizenewareas,regardlessof thepresenceofmacrocystis.

7 ACKNOWLEDGEMENTS Obtainingamaster sthesisinmarinescienceisaninherentlyselfish endeavor.ittakesanextensiveinfrastructure,alargecommunityofinvolved academics,andinthecaseofthisthesis,lotsofdiverswillingtoendurecold, turbulent,shark infestedwatersforlittlemorethancheeseandcrackers. ThroughoutmytimehereatMossLandingMarineLabsIhavebeensuppliedwitha greatdealofresources,andhavealwayshadaconstantsupplyofacademicinsight andfieldhelp.mosslandingmarinelaboratoriesisaveryspecialplace,filledwith amazingpeople. Dr.MichaelH.Grahamisagreatscientistandwasafantasticadvisor.He lovesanythingthatfocusesonecology,kelp,orbacon.mikebothgavemethe freedomtoworknearlyautonomouslywheniwanted,andhewasalmostinstantly accessibletohelpmewitheveryproblemthatifaced.mylabmates,theself titled BEERPIGS,arethemostcriticalandanalyticalgroupofecologistsIhaveeverhad thepleasureofworkingwith.theirconstantevaluationofmythesisateverystage couldbemaddening,butithasmademeabetterscientist.andwhenitcametime tocollectdata,theywerealwaysthere,willingtodowhateveriaskedofthem,even whentheywerebettingitwouldn twork.iamindebtedtodaniellefrechettefor multipleeditsofthismanuscript,andforherpatience.finally,myparentshave encouragedmyinquisitivenesssincebeforeicouldwalk,andhavegivenmeevery kindofsupportpossible.iloveyouboth.thankyou. v

8 TableofContents INTRODUCTION...1 METHODS..10 BigCreekMarineReserve(BCMR) StillwaterCove(SWC) 16 StatisticalMethods.19 RESULTS BigCreekMarineReserve..21 StillwaterCove..29 DISCUSSION.45 LITERATURECITED..58 vi

9 ListofFigures Figure1:Locationofstudysites. 12 Figure2:TotalpercentcoverofalgalfunctionalgroupsbetweenBCMR 22 andswc,spring2008. Figure3:NereocystisrecruitmentatBCMRsampledin Figure4:MacrocystisrecruitmentatBCMRsampledin Figure5:PterygophorarecruitmentatBCMRsampledin Figure6:DesmarestiarecruitmentatBCMRsampledin Figure7:RecruitmentofNereocystisatSWC. 32 Figure8:RecruitmentofNereocystisatSWCbetweenplotsseededwith 34 additionalzoosporesandcontrol( unseeded )plots. Figure9:RecruitmentofMacrocystisatSWCin Figure10:PterygophorarecruitmentatSWCin Figure11:DesmarestiarecruitmentatSWCin vii

10 ListofTables Table1:Split levelanova(typeiii)ontheeffectsofcanopy 30 andunderstoryontherecruitmentofnereocystisatbcmr. Table2:Split levelanova(typeiii)ontheeffectsofcanopy 30 andunderstoryontherecruitmentofmacrocystisatbcmr. Table3:Split levelanova(typeiii)ontheeffectsofcanopy 31 andunderstoryontherecruitmentofpterygophoraatbcmr. Table4:Split levelanova(typeiii)ontheeffectsofcanopy 31 andunderstoryontherecruitmentofdesmarestiaatbcmr. Table5:IndependentSamplest Testscomparingrecruitment 43 ofnereocystisinswcbetweenplotsseededwithadditional zoosporesandplotswithnoadditionalinputofreproductive material(alltreatmentspooled). Table6:IndependentSamplest Test.Recruitmentof 44 NereocystisatSWCbetweencanopyandno canopy treatments. Table7a:Split levelanova(typeiii)ontheeffectsofcanopy 44 andunderstoryontherecruitmentofmacrocystisatswc. Table7b:One wayanovaontheeffectsofcanopyand 45 understoryontherecruitmentofmacrocystisatswc. Table8a:Split levelanova(typeiii)ontheeffectsofcanopy 45 andunderstoryontherecruitmentofpterygophoraatswc. Table8b:One wayanovaontheeffectsofcanopyand 46 understoryontherecruitmentofmacrocystisatswc. Table9:Split levelanova(typeiii)ontheeffectsofcanopy 47 andunderstoryontherecruitmentofdesmarestiaatswc. viii

11 Introduction Nereocystisluetkeana(Mertens)Postels&Ruprechtisalarge,conspicuous kelpthatformsdensecanopiesinshallowcoastalwatersofthepacificnortheast (Frye1906).Classifiedasaspringannual(AbbottandHollenberg1976)orasa springopportunist(daytonetal.1984),nereocystishasaheteromorphiclife history,withanalternatingmacroscopicsporophytestageandamicroscopic gametophytestage.incentralcalifornia,themacroscopicsporophytestageis typicallyfirstobservedintheearlyspring(mclean1962,fosterandschiel1985), andindividualplantscanbecomereproductiveshortlybeforereachingthesurface inmay(abbottandhollenberg1976).theseindividualsmayformadensecanopy thattypicallyreachesmaximumcoverageinthefallbeforebeingdislodgedbythe firstwinterstormsoftheyear(foster1982).whenpresent,theselargenereocystis bedscanformbiologicallycomplex,three dimensionalstructures.awidearrayof invertebrates(mclean1962)andfish(bodkin1988)associatewiththesebeds. LittledirectworkincentralCaliforniahasbeendoneonthephysicaleffects thatnereocystisbedscanexertontheirenvironmentandonotheralgal assemblages.ithasbeenwelldocumented,however,thatotheralgalcanopyand understorylayerscanreducethelightto<1%ofsurfaceirradiance(daytonetal. 1984,ReedandFoster1984,Clarketal.2004).Suchadrasticreductioninlight reachingthebenthosreducesorcancompletelyinhibitkelprecruitment,sometimes forseveralyears(edwards1998,clarketal.2004).certainkelpspeciescan directlyinfluencethesurroundingvegetationviaabrasion(irving&connell2006, 1

12 Hughesinreview),shiftingthesurroundingalgaefromerectcorallineorfleshy speciestooneswithcrustosemorphologies.densemacrocystisbedsinsouthern Californiacanalterthevelocityanddirectionofcurrents(Jackson1997),whichin turnincreasesthelikelihoodthatpropagulesareretainedwithinthecentersoflarge beds(graham2003).currently,itisuncleartowhatdegreenereocystiscanalter thephysicalenvironmentandassociatedbiota,andwhethernereocystiscan competeandpersistinareasoccupiedbyotheralgalspecies.asacanopyproducingannual,itcanreachgreatdensities,particularlyduringthelatesummer, yetitisfunctionallyabsentforseveralmonthseachyear(frye1906,fosterand VanBlaricom2001).Nereocystismighthaveastrongandlastingeffectonthe surroundingbiotabecauseitreachessuchdensitiesduringthesummer,oritmay haveaweakandperiodiceffectduetoitsseasonality. TheecologicalrangeofNereocystisstretchesfromPiedrasBlancasincentral CaliforniatoUnimakIslandintheeasternAleutians,Alaska(MillerandEstes1989). Withinthisrange,Nereocystisisfoundattachedtohardsubstrate,frequentlyon wave sweptpointsandrockyoutcroppings.theseindividualscanformlargebeds wherealltheadultsporophytesmayberemovedeachwinter,butarereplacedby newrecruitsthefollowingspringandsummer.thiscontinuanceofakelppatch throughmultiplegenerationsmeetsthedefinitionofpersistence(daytonetal. 1984),despitethepatchbeingcompletelyabsentforseveralmonthseachyear. Persistencehasbeendefinedasthe existenceofapatchformorethanone generation (Daytonetal.1984)andhasbecomeakeycomponentindefiningthe 2

13 stabilityofapopulationandofanentireecosystem(connellandsousa1983, Daytonetal.1984). Duringwintermonths,strongsouthernstormscannearlyorcompletely removeanareaofallnereocystissporophytes(foster1982).inordertopersist (Daytonetal.1984),akelpbedmustrelyonthesuccessfulrecruitmentof microscopicgametophytesintosporophytesthefollowingspring(seedixonand Waaland1985forsynopsis).AsinglehealthykelpplantsuchasMacrocystisis capableofreleasingover100millionzoosporesinasingleseason(kritzerandsale 2006).InNereocystis,meiosisoccursinspecializedregionsofthebladecalledsori (AbbottandHollenberg1976).SorifirstappearonthebladeinMayandare producedcontinuouslyuntiltheplantisrippedoutbywinterstorms(foster1982). Haploid,bi flagellatezoosporesarereleasedenmassfromthesepatchesintothe watercolumn.thesereleasesmaybecuedbydaylight,withthemajorityofthe zoosporesbeingreleasedwithinafewhours(amslerandneushul1989).these patchesthenabscizefromthebladeandfalltothebenthos,wheresomecontinued, localizedreleaseofzoosporesmayoccur(amslerandneushul1989). Dispersalofkelppropagulesishighlyvariableandepisodic(Reedetal. 1988).Zoosporesarephotosyntheticandcanswiminthewatercolumnforgreater than72hours(reedetal.1992),greatlyenhancingthedistancetheycanbe dispersedbyoceancurrents.however,theadultgametophytesbornefrom zoosporesaresessileanddioecious.settlementdensitiesinexcessof1/mm 2 are necessaryforsuccessfulfertilizationandgametogenesistooccur(reed1990). 3

14 Zoosporeswhichtraveloutsidethekelpbedaremorelikelytobecarriedawayfrom thebed(jackson1977,graham2003)andmaynotsettleinsufficientdensitiesfor fertilizationtooccur(reed1990).kelpsreadilyhybridizeandselffertilize(lewis andneushul1995,druehletal.2005),suggestingthatasingleadultsporophyte couldcolonizeanentirearea,butself fertilizationeventstendtoyieldindividuals withreducedfitness(raimondietal.2004). Completionofthegametophytegenerationisdensity dependent,therefore, zoosporesmusteithersettletogetheringreatnumbers,orthemicroscopic gametophytesmustsurvivelongenoughforanotherzoosporetosettlenearby.the potentiallongevityofakelpgametophyteisintenselydebated.thesporophytesof kelpannualsfrequentlyareabsentforatleastaseasoneachyear,anditgenerallyis acceptedthatmicroscopicstagescanpersistforatleastthislong.aseriesof laboratory(edwards1998,mcconnico2002,carneyetal.2005)andfield experiments(edwards2000,mcconnico&foster2005)supportthisidea. However,itisunclearwhethermicroscopicstagescanpersistforgreaterthanone year,anditalsoisunclearwhattheirpreciseidentity(i.e.spore,gametophyteor embryonicsporophyte)maybeduringthesemicroscopicstages(seereedetal. 1997,Kinlanetal.2004,Edwards2005) IncentralCaliforniathereisalarge(~240km)regionofcoastlineranging frompiedrasblancasinthesouthtoañonuevoislandinthenorthwherethe distributionofnereocystisoverlapswiththeperennialkelpmacrocystis.withinthis area,thesetwospeciesoftenformpersistent,monospecificbedsthatareoften 4

15 adjacenttoeachother(crandall1915,foster1982),withthenereocystisbeds frequentlyinshallowerwateroralongmorewave sweptpoints(kalvassand Larson2004).ThisobservationofNereocystispersistingonlyinmorehydrodynamicallyextremeenvironmentssuggeststhatMacrocystisiscompetitively dominantovernereocystisinallbutthemostextremeenvironments.whereasthe greatermass(faye1915)andhighdragofadultmacrocystisplants(jackson1997) mayexplainwhymacrocystissporophytesdonotpersistalongthesewaveswept pointsbutnereocystissporophytesdopersist(dennyetal.1997),itisunclearwhat preventsnereocystisfrominvadingareaspresentlydominatedbymacrocystis. NumerousstudiesincentralCaliforniahavedemonstratedthataMacrocystisbed canformasurfacecanopythickenoughtoreducesurfaceirradiancebymorethan anorderofmagnitude(edwards1998,clarketal.2004). Lackingfromtheliteraturearetargeted,insituexperimentsdesignedto examinetheecologicalroleofnereocystisincentralcaliforniawhereitcoexistswith theperennialmacrocystis.theimportanceandrelevanceofaspeciesisoftentiedto itsstability(connellandsousa1983).forpatch forming,sessilespeciessuchas kelps,stabilitycanbemeasuredbyconsideringthepersistence,inertia,and resilienceofthepopulationoverseveralgenerations(daytonetal.1984).whereas persistenceistheabilityofaspeciestooccupythesamelocationthroughmultiple generations,inertiaandresilienceconsidertheabilityofaspeciestocolonizenew areas,andpreventotherspeciesfromencroaching,respectively.whilemanyhave notedthepersistenceofnereocystisbedsonwave sweptpoints(frye1906,foster 5

16 1982,Daytonetal.1984,Foster&VanBlaircom2001),theinertiaoftheseplantsto invadenearbymacrocystisbedshaveroutinelybeencalledintoquestion(foster 1984,Daytonetal.1984);incentralCaliforniaNereocystisisassumedtobe competitivelyinferior,despiteanydirectexperimentalstudiestotestthis hypothesis.thisisdueinparttothedifficultiesofworkinginswellexposedareas wherenereocystisoccurs(foster1982),whichoftenarelocatedawayfromharbors andshoreaccesspoints(kalvassandlarson2004).manipulativestudiesof Nereocystislargelyhavebeenconductedinthelaboratory(e.g.Vadas1972,Duncan andforeman1980,lüning&freshwater1988,amsler&neushul1989,atriumet al.1994,dennyetal.1997). Previousfield basedstudiesofnereocystiseitherweresurveysofextantor historicalbeds(crandal1915,frye1915,scagel1945,foreman1970,berryetal. 2001&2005),orsimplequantificationsofthemarineorganismsassociatedwith Nereocystisplants(seeAndrews1945,Markham1969,Bodkin1986).Themajority ofrecentfield basedstudieshavebeenconductedinmorenortherlyareaswhere Macrocystisisabsent(MaxellandMiller1996,Carneyetal.2005). Thepurposeofthisstudywastodetermineifeitherdispersalofpropagules orcompetitionbetweenotherspeciesofseaweedcouldaffecttherecruitmentof Nereocystis,andthereforeexplainwhyNereocystisonlyformspersistentbedsalong wave sweptpointsincentralcalifornia.toprovidecontexttotheresults,the recruitmentoftheannual,canopy producing 6

17 Nereocystiswascomparedwiththreedistinct,wellstudiedspeciesofbrown seaweeds,eachwithslightlydifferentlife historycharacteristics. Macrocystispyriferawaschosenbecauseitisageneticallysimilar(Laneetal. 2006),perennial,canopyproducingkelp(AbbottandHollenberg1976).Unlike Nereocystisitcanbepresent,reproductive,andrecruityear round(graham2003). Macrocystismaybethemoststudiedofallkelpsinthisregion.Recruitmentof Macrocystishasbeenexperimentallystudiedinsitu(ReedandFoster1984,Foster andscheil1984,daytonetal.1984&1992,konar1996,reedetal.2000,graham 1996,Clarketal.2004)andunderlaboratoryconditions(Lüning1988,Reed1990, Reedetal.1996&1997,Kinlanetal.2003).LikeMacrocystis,Pterygophora californicaisaperennialkelp.however,pterygophoraisanunderstorykelp(i.e.it doesnotformasurfacecanopy)andithasaverydefinedandnarrowrecruitment window(reedetal.1997),similartowhatmanyexpectaspringannualkelpsuchas Nereocystistohave.FollowingtherecruitmentofbothPterygophoraand Macrocystisallowstwoperennialkelpswithextremesinboththeirsize(canopyand understory)anddispersalwindows(narrowandcontinuous)tobecomparedwith therecruitmentofnereocystis.desmarestialigulataisnotakelp,butabrown seaweedofthecloselyrelateddesmarestiales(abbott&hollenberg1976).like Nereocystis,Desmarestiaisanannualwhichcanrecruittorecentlydisturbed patches(edwards1998),sometimesinsuchgreatdensitiesthattheemergingadults canpreventallotheralgaerecruitment(dayton1992,clarketal.2004). RecruitmentofthisseaweedincentralCaliforniaisthoughttobelimitedessentially 7

18 toaverynarrowwindowinapril.nereocystisincentralcaliforniaisunique,asitis theonlycanopyformingannualkelp.macrocystis,pterygophora,anddesmarestia createacollectionofthreetraitsagainstwhichtocomparetherecruitmentof Nereocystis(Table1).Thesethreetraitsare1)whetherthealgaeformsacanopy,2) whetheritisanannualoraperennial,and3)whetherithasalimitedorbroad recruitmentwindow. AdensecanopyofMacrocystisfrondscanreducesurfaceirradiancetothe benthosbygreaterthananorderofmagnitude(clarketal.2004),whichinturncan limitorevencompletelyprohibittherecruitmentofmanyspeciesofkelp(reed& Foster1984,Daytonetal.1992,Edwards1998).Itisuncertainwhethera Nereocystiscanopycancreatethesamemagnitudeofeffectthatadeveloped Macrocystiscanopycanhave.Perennialkelpshavethepotentialofbeingpresentfor severalyears,whereasakelpwithanannuallife historybydefinitionisabsentfora portionofeachyear.whethernereocystis,anannual,canaffectsubsequentalgal recruitmentatallisundetermined,andifso,duringwhichmonthsoftheyear. Finally,thedurationofthe recruitmentwindow ofasessilespeciescanhavea lastingandbroadimpactonabilityofthatspeciestopersistinanarea,andrecover followingadisturbance.inspecieswithlimitedrecruitmentwindows,recruitment occursduringabriefperiodoftime,oftenswampingsimilarspecies(reedetal. 1990),butrequiresatemporallyreliablepatternofdisturbance.Broador continuousrecruitmentwindowsdonotrelyonsuchtemporaldisturbancebut 8

19 requireeitheraprolongedmicroscopicstage(dayton1985)oracontinuousrelease ofnearbyzoospores(kinlanetal.2004). TheobjectiveofthisstudywastoexamineNereocystisrecruitment. Specifically,threequestionswereaddressed.1)DoesNereocystishavealimitedor broadrecruitmentwindow?2)isnereocystiscompetitivelyinferiortomacrocystis; (i.e.isthepresenceofamacrocystisbedenoughtopreventcolonizationof Nereocystisintotheseareas)?,and3)IsrecruitmentofNereocystisintoanearby Macrocystisbedlimitedbythedispersaldistanceofitspropagules;givenasufficient supplyofzoospores,cannereocystissuccessfullyrecruitintoanexistingmacrocystis bed? Whilethisapproachfocusesondirectobservationofonlyonestageofa kelp scomplexlifehistory,byexaminingrecruitmentagreatdealcanbeinferred. Successfulrecruitmentrequirescompletionofthemicroscopicstages.Areaswith lowerobservedrecruitmentmayeitherhavehadlowersettlementofpropagules,or thenewcohortofemergingsporophytesdidnotgrowandsurvivelongenoughto becounted.regardless,inanannualpopulationofsessileindividuals,recruitment failurewillcausethatpopulationtobecomeextinct. 9

20 Methods Inordertoeffectivelytestthethreequestionsoutlinedpreviously,twofield siteswerenecessary.onesitewaslocatedwithinapersistentnereocystisbed wherepropagulesupplywasassumedtobeatmaximum,andthesecondsitewithin amacrocystisbednotfarfromreproductivenereocystisadults.whereasthe methodsdescribedbelowaresimilarforbothsites,eachlocationalloweddifferent aspectsoftheresearchquestionstobeaddressed.thesitewithinanereocystisbed providedabaselineofnaturalnereocystisrecruitment,ittestedtheeffectofa Nereocystiscanopyonitsownrecruitmentandbytrackingrecruitmentthroughout aseason,itwouldbepossibletodeterminewhethertherecruitmentwindowwas limitedtoaverynarrowtimeoryearormorebroadandcontinuous.havingasite withinapersistentmacrocystisbedallowedaparallelsetofquestionstobe addressed.ithasbeensuggestedthatnereocystismaybecompetitivelyinferiorto Macrocystis.ByremovingtheMacrocystiscanopythisideaofdirectcompetitive dominancecanbeaddressed.also,ithasbeenhypothesizedthattherecruitmentof Nereocystisintonewareasmaybelimitedinpartbythedispersaldistanceofits propagules.experimentalplotswithinamacrocystisbedalmostcertainlyhave fewernereocystispropagulesthanthoselocateddirectlywithinanereocystisbed, andtheobservedrecruitmentcanbeusedtodetermineiftheabilityofnereocystis tocolonizenewhabitatmaybelimitedbydispersaldistance. Thetwositeswereselectedforthisexperiment,BigCreekMarineReserve (hereafterbcmr)andstillwatercove(hereafterswc).inadditiontohavinglarge, 10

21 persistentnereocystisandmacrocystisbeds(respectively),thesetwolocationseach offeredalarge,relativelyflatareaofhardsubstratewithminimalsandcoverat8 10mMLLWandreasonableaccesstodivers.Specificsitelocationswereselectedin Fall2007,correspondingtotheexpectedmaximumkelpcanopycover(Donnellen 2003).Withtheexceptionofdeployingsitemarkersandinitialsurveysofthebiota in2007,allfieldworkwasconductedbetweenfebruaryandnovember2008. BigCreekMarineReserve(BCMR) BCMRwaslocated4milesnorthofLuciaalongtheBigSurCoastline(36º N,121º W Figure1).Itwascomposedofgraniticrockfromthe SantaLuciarangeandconsistedofamixedcanopywithinthecoveandlarge Nereocystisbedstothenorthandsouthofthecove. 11

22 Figure1:Locationofstudysites. Experimentalplotswereestablishedin2007insidetheannualNereocystisbed locatedtothesouthofthecove.criteriaforsiteselectionwerethepresenceofa densenereocystiscanopy(infallof2007),apredominanceoflowreliefrock outcropsatadepthof8 10mMLLW,andverylimitedsandcover.Tominimizethe inputofmacrocystispropagules,allplotswereestablishedatleast200metersfrom thenearestmacrocystisbedtothenorth,andtheseplotsranroughlyparalleltothe 12

23 shore.tenplots,each10metersindiameter,wereestablishedinthefallof2007 andmarkedbyasurfacefloatattachedtoastainlesssteeleye boltinthecenterof eachplot.theedgeofeachplotwasatleast10metersfromtheedgeofany adjacentplots.withineachplot,sixsubplots(1meterindiameter)werecreatedby haphazardlyselectingareasofexposedbedrockwithlowreliefandminimalincline. Thesehaphazardlyselectedsubplotsweremarkedbyalag boltinthecenterofeach plotandthenrandomlyallocatedusingasix sideddieintoeitherscrapedplotsor controlplots(eachn=3).subplotswereatleasttwometersfromoneanother,from thecentermarkerbuoy,andfromtheedgeoftheplotstomaintainindependence fromunderstoryandalgalturfassemblages. Inthefallof2007thefollowingwasdonewithineachplot.Thethree subplotsrandomlyallocatedas scraped wereclearedbydiversonscubaofall macroscopicalgaeusingacombinationofknivesandpaintscrapers.pterygophora californicathalliwerecutwithin5cmoftheholdfastsandremovedfromtheplots completely.theremainingholdfastswereleftinplacebecauseremovingthemcan resultinfragmentationoftheunderlyingrock,andbecausetheycanserveas recruitmentsubstrateforotherkelpspeciesincludingnereocystisluetkeana (Kennelly1987).Encrustingcorallinesandinvertebrateswereleftrelatively unmolested.thecorresponding3unmanipulatedsubplotsweremarkedina mannersimilartothe scraped subplotsbutwereotherwiseleftunchanged.this processwasrepeatedforall10plots.toaidinunderwaternavigationalead line connectedthecenterboltsofeachplot,anchoredinplacesbydestroyerchainand 13

24 eye bolts.greatcarewastakentoensurethatthelead linewouldnotcrossintoany scraped or unmanipulated subplots,evenunderheavysurge. Fiveoutof thetenplotswererandomlyselectedas nocanopy plots.beginninginaprilof 2008andcontinuingthroughouttheexperiment,anycanopy formingkelpspecies werecutbydiversandallowedtodriftaway,beforetheycouldreachthesurface andformacanopy.intheremainingfiveplotsacanopywasallowedtoform naturally. Thispatternofrandomlyallocatedfactorsarrangedwithinoneoftwo blockingfactorscreateda splitplot design.inthiscase,thepresenceorabsenceof acanopywastheblockedfactor.withineachcanopytreatmentthereweretwo replicated,randomlyassignedtreatments:a scraped treatmentwhereallfleshy algaewereremoved,andan understory treatmentwherethealgalassemblages werepermittedtodevelopunperturbed.this split plot designwaschosen becausethetwoassemblagesbeingconsidered,canopy&understory,operateat verydifferentspatialscales.canopyproducingkelpsin10mdepthcanshadea largeareaofthebenthos(seedaytonetal.1984),whichrequiredthelarge10m diameterplots.however,thesignificantlysmallerunderstoryandturfalgae physicallyaffectmuchsmallerareas,allowingthesetreatmentstobesplitand replicatedwithintheblocked,canopyfactor. Thissplit plotdesigncreatedfourdistincttreatments:understory/with canopy,understory/nocanopy,scraped/withcanopyandscraped/nocanopy. BecauseadultNereocystisandMacrocystissporophytescanbecomeverylargeand 14

25 havethepotentialtophysicallyshadeaverylargeareaitwasnecessarytogroup thesubplotstowardsthecentertoreduceedgeeffectsbycreatingalarge buffer zone betweentheedgeoftheplotsandthesampledsubplots. Allscrapedplotsweresurveyedeachmonth,beginninginMarch2008,which wasbeforethefirstanticipatedannualkelprecruits(pers.obs,butseeedwards 1998andMcConnico2003).Aftereachsampling,allfleshyalgaewithinthe scraped subplotswerecarefullyremovedtoensuretheirphysicalpresencewould notinfluencesubsequentrecruitment. AllsubplotsweresampledonceperseasonbydiversonSCUBA.Withinthe scrapedplots,diversidentified,measured,recordedandthenremovedallkelp recruitsanddesmarestiarecruitswithina1mdiametercirclearoundthecenter markerbolt(0.79m 2 ).Aftereachscrapedplotwassampled,allfleshyalgaebesides juvenilekelpswereremovedbyhandtoensurethepotentialrecruitmentarea remainedcomparablethroughouttheexperiment.juvenilekelpstoosmalltobe identified(generally<6cmtl)weremeasuredbutallowedtopersistuntilthenext samplingperiod,whentheyhadpresumablyeithergrownenoughtobevisually identifiedtospeciesorbeenremovedbynaturaldisturbances.desmarestiaspp. recruitswereeasilyidentifiableassoonastheywerelargeenoughtobecounted (Edwards1998).Samplingwassimilarintheunmanipulatedcontrolplots,however nofleshyalgaewereremoved,andtheplotswereallowedtodevelopnaturally throughouttheexperiment. 15

26 SecondonlytothecanopyformingNereocystis,themostconspicuousalga withinthesouthernkelpbedatbigcreekwastheperennialkelppterygophora.the densityofpterygophorawasestimatedduringthefallof2007bycountingall individualswithin2x10mband transects(n=3).duringtheinitialestablishment ofthescrapedplotsthe5pterygophoraplantsclosesttothecenterboltwerechosen toestimateaveragesizeandage.inthefieldtlofthethalluswasrecorded,anda shortsegmentofthestipelocated~5cmabovetheholdfastwasremovedtobeused forageanalysis.agewasdeterminedbycross sectioningthestipeandcountingthe rings(methodsofhymansonetal.1990). AlgalcoverwasmeasuredinMayandJune2008usingasimpleRandom Point Contact(RPC)method.ArigidPVCbar,0.5minlength,washaphazardly placedacrossthecenterboltofthe understory subplots.thisrigidbarhada stringwithfiveknotsservingas points.ateachpointthediverwouldpullthe stringtautaboveandbelowthebarandrecordwhateverspeciesfellunderthose twopoints.thebarwouldthenberotated90ºandtheprocessrepeated,givinga totalof20randompointsineachsubplot.becausethe scraped plotswere routinelydisturbedandremovedoffleshyalgae,onlytheunmanipulated understory plotsweresampledusingthismethod. StillwaterCove(SWC) TheSWCstudysitewaslocatednearCarmel,justsouthoftheMonterey Peninsula( N, W Figure1).Itwascharacterizedbyadense 16

27 Macrocystiscanopythroughoutthecove,withasparseNereocystiscanopyjustnorth ofthecove.thecoveopenedtothesouthandwasrelativelyprotectedfromthe northwestswellscommontothecoastofcentralcaliforniacoast.duringwinter,the lessfrequentsouthernswellsremovemostofthemacrocystiscanopy(foster1982, ReedandFoster1984).Thelargeunderstoryassemblagesweredominatedby Pterygophoracalifornica,withCystoseiraosmundaceaandChondracanthus corymbiferusalsopresent.adenseturfassemblageofgeniculatecorallinealgae coveredmostavailablerocksubstrate(seereedandfoster1984).patchesofsand frequentlyintrudedoverthebedrock.criteriaforsiteselectionwerethepresenceof adensemacrocystispyriferacanopy(duringfall2007),apredominanceoflowrelief rockoutcroppingsat8 10mandlimitedsandcover. TheexperimentaldesignatSWCutilizedasplit plotdesignsimilartothe designusedatbcmr.twelveplotswereestablishedwithinthekelpforestatswc. Sixofthesetwelveplotswererandomlychosentobe nocanopy treatments.all canopy formingkelpswereremovedfromtheseplotsinmarch2008,anddivers periodicallyremovedanynewjuvenile,canopyformingkelpsaswellasthe reproductivefrondsofcystoseiraosmundacea.thispreventedacanopyfrom formingwithintheseplotsduringtheexperiment.acanopywasallowedtoform naturallyintheremainingsix canopy plots. Withineachplot,sixsubplotswereestablished,each1mindiameter.During thefallof2007,threeofthesubplotswithineachplotwererandomlyselectedas scraped treatments,andwereclearedbydiversusingacombinationofknivesand 17

28 paint scrapers.theremainingsubplotsweremarkedbutotherwiseleftasan unmanipulated understory treatment. Thissplit plotdesigncreatedfourdistincttreatmentsinswc: Understory/withcanopy,scraped/withcanopy,understory/nocanopy,and scraped/nocanopyareequivalenttothesamefourtreatmentscreatedinsidethe NereocystisbedatBCMR.Inadditiontothesefourtreatmentssharedbetweenthe twostudysites,anadditionalfactorwascreatedatswctotestwhetherrecruitment ofnereocystiswaslimitedbydispersalandsuccessfulsettlement.atotalofsixplots (threecanopyandthreeno canopy)were seeded withreproductivenereocystis soriduringthefallof2007.ripesorifromseveraldifferentreproductive Nereocystissporophyteswerecollectedfromapopulationlocatedabout0.5km fromtheexperimentalplots.thesesoriweremixedtogethertoreduceselfingand placedintomeshbags.themeshbags,weightedbylargegranitecobble,were placeddirectlyontopofallsixsubplots(scrapedandunderstory).thesemeshbags wereallowedtositonthebottomfor~72hoursbeforebeingretrievedbydivers. This sporeseeding wasrepeatedtwiceduringfall2007,andwassimilartothe methodusedbydaytonetal.(1984).this seeding ofsubstrateservedto determinewhethersuccessfulzoosporesettlementwaslimitingsubsequent recruitment.however,whenanalyzingnereocystisrecruitmentthisdoubledthe numberoftreatments(i.e. seeded,scraped/nocanopy and notseeded, scraped/nocanopy )andreducedthesamplesizebyhalf. 18

29 PterygophoradensitywasestimatedduringFall2007utilizingthesame methodsusedatbcmr(2x10mbandtransect,n=3).basicalgalcoverwas measuredduringmay2008.algalcoverwasdeterminedbyasimplerandom Point Contactmethod.ArigidPVCbar,0.5minlength,washaphazardlyplaced acrossthecenterboltofthe understory subplots.thisrigidbarhadastringwith fiveknotsservingas points.ateachpointthediverwouldpullthestringtaut aboveandbelowthebarandrecordwhateverspeciesfellunderthosetwopoints. Thebarwouldthenberotated90ºandtheprocessrepeated,givingatotalof20 randompointsineachsubplot.becausethe scraped plotswereroutinely disturbedandremovedoffleshyalgae,onlytheunmanipulated understory plots weresampledusingthismethod. StatisticalMethods AlldatawereanalyzedusingSPSSv statisticalpackageforMac. Speciesstudiedhadknownrecruitmentstrategiesthatvariedfromcontinuousto extremelylimitedintime.theprimaryinterestwasintheeffectofthecanopyand understoryonrecruitmentofnereocystisratherthaninthedifferencein recruitmentofonespeciesbetweenmonths.wheneverrecruitswereobservedin alltreatmentsasplit levelanova(typeiii)wasused(appendixx).the assumptionofnormalitywasconfirmedusingakolmogorov Smirnovtest,whereas theassumptionofequalvarianceswasassessedbyexaminingtheresiduals.when theassumptionofequalvarianceswasnotmet,thedatawaslog transformed.in 19

30 thecaseswhereoneormoretreatmentsfailedtoyieldanyrecruitmentaone way ANOVAwasused,becauseasplit levelanovacannotberunwhenoneormore treatmentsyieldsavalueofzero.whenaone wayanovademonstrateda significantdifferencebetweentreatments,apost hoclsdtestwasusedto determinewhichtreatmentsdiffer. 20

31 Results BigCreekMarineReserve ThealgalassemblagesatBCMRweredominatedbytwokelps,theperennial understorykelppterygophoraandtheannualcanopyproducingkelpnereocystis. Thedensitiesandlargeindividualsizesofthesetwospeciesfarexceededthe abundanceofallothermacroalgae.adultpterygophoradensityasmeasuredinfall 2007was9.2individuals/m 2 (+/ 1.7SE).Whileonlyasubsampleofplantswere directlymeasured,manyoftheseindividualsexceeded150cmtl,withone individualobservedtobe210cm.theunderstorycanopycreatedbythe Pterygophoraplantswasdense,oftenapproaching100%cover;itwasdifficultor impossibletoseethesubstrateoranyturfalgaefromdirectlyabovetheseplants. StiperingcountsindicatedthattheaverageageofthesePterygophoraplantswas 3.9years(+/ 1.7SE,n=30). Beinganannual,it sunsurprisingthatnereocystiswentfromlowtohigh densitieswithinafewmonths.whileafewsporadicandhighlybatteredindividuals wereobservedfromthesurfacetohaveoverwintered,notasinglenereocystis sporophytewasobservedduringasurveydiveinmarch2008withintheten,10m diameterplots(0individualsin790m 2 ).BytheAugustsampling,thedensityof Nereocystisadultplantswithinthefivecanopytreatmentshadreached0.29/m 2 (+/ 0.05SE),oraboutoneplantevery3.5/m 2. RPCdataconductedwithinthe understory treatmentsinjune2008showed thatmostofthesubstratewascoveredbysessileinvertebratesorencrustingalgae. 21

32 Theseencrustingspeciescovered68%ofallavailablespace(Figure2).Geniculate corallinesdominatedallerectalgalspecies(16%totalcover).non calcified,fleshy redalgaeaccountedfor9%ofallsurfacecover,andkelpholdfastsanddesmarestia eachoccupied6%.afewotherspeciesofbrownalgae(namelycostariacostata) wereobservedbutwererareandpatchy,andwerenotcapturedbytherpcmethod. Thesessileinvertebrateandencrustingalgaecategorieswerecombinedbecausea heavylayerofsiltandlowlightunderthepterygophoracanopymadeidentification ofeachspeciesextremelydifficult. Figure2:TotalPercentCoverofalgalfunctionalgroupsbetweenBCMRandSWC, Spring2008(meanofall12plots/site,withn=3samplestakenwithineachplot,+/ SE) TheNereocystiscanopyatBigCreekMarineReservedevelopedpredictablyin2008, firstreachingthecanopyinmayandgrowingincreasinglydensethroughthe summerandintothefall(pers.ob.).nereocystisrecruitswereobservedinall 22

33 treatmentsbothinjuneandaugustof2008,withrecruitmentgreatestduringthe spring(figure3).recruitmentinjunerangedfrom17.5/m 2 +/ 4.2SEinsidethe scraped,withcanopy treatmentsto1.1/m 2 +/ 0.6SEinsidethe understory/no canopy treatments.duringthejunesampling,recruitmentwassignificantly differentandanorderofmagnitudegreaterinscrapedplotsthaninplotswherethe understoryhadbeenleftalone(p<0.001,table1).thepresenceofacanopyhadno discernibleeffectonrecruitment(p=0.361),despitenumerousplantsthathad reachedthesurfacewithineachplot.whileoverallrecruitmentwaslowerin AugustcomparedtoJune,thepatternsofrecruitmentduringAugustmimicked thoseseenearlierintheseason.inaugust,recruitmentwasagaingreatestwithin scrapedsubplots(p<0.001). Recruits per square meter June Scraped, No Canopy Scraped, With Canopy Control, No Canopy Control, With Canopy August Figure3.NereocystisrecruitmentatBCMRsampledin2008(mean+/ SE,n=6). 23

34 TherewasnosignificanteffectoftheNereocystiscanopyonNereocystisrecruitment, andtheinteractionbetweencanopyandunderstorywasalsonotsignificant (p=0.361injuneandp=0.512inaugust),suggestingthecanopyneverbecame denseenoughtoretardrecruitment. RecruitmentofMacrocystispyriferaattheBigCreeksitewaslowthroughout theexperiment,withthenumberofrecruitsatorbelow1/m 2 acrossalltreatments andsamplingperiods(figure4).thislowlevelofrecruitmentwasconsistentwith anareawithfewnearbyadultmacrocystissporophytes. Recruits per square meter June Scraped, No Canopy Scraped, With Canopy Understory, No Canopy Understory, With Canopy August Figure4:MacrocystisrecruitmentatBCMRsampledin2008(mean+/ SE,n=6). 24

35 DuringtheJunesampling,Macrocystisrecruitmentwassignificantlygreaterwithin scrapedplots(p=0.005,table2).thisdifferencewaslessdistinctduringtheaugust sampling(p=0.051).aswithnereocystisrecruitment,canopyhadnosignificant effectonmacrocystisrecruitmentduringtheexperiment. WhereasDesmarestiahadmostofitsrecruitmentduringtheJunesampling, Pteryogorphoracalifornicashowedtheoppositepattern(Figure5).Recruitmentof PterygophorawasverylowduringJune,withthelargestnumberofrecruits occurringin scraped/nocanopy plots(1.8recruits/m 2,+/ 0.62SE). %! )$*+",('-.$+-'/"0+$-1$($+ $! #! "! &'()*+,-./0.1)20*3 &'()*+, )20*3 82,+(960(3-./0.1)20*3 82,+(960( )20*3!!"#$ %"&"'( Figure5:PterygophorarecruitmentatBCMRsampledin2008(mean+/ SE,n=6). Scrapedplotsshowedsignificantlygreaterrecruitmentthanplotswherethe understoryalgaehadbeenleftintact(p=0.027,table3),howeverthepresenceof 25

36 thecanopywasdeemednon significantduringjune(p=0.369).augustrecruitment ofpterygophorawasmorethananorderofmagnitudegreaterthanjune recruitment.duringtheaugustsamplingperiod,the scraped,nocanopy plots hadatleasttwicethedensityofrecruitmentcomparedtoanyothertreatment. Scrapedplotshadsignificantlygreaterrecruitmentthanplotswheretheunderstory wasleftintact(p=0.001),andplotswherecanopyhadbeenremovedalsoshowed significantlygreaterrecruitment(p=0.001).additionally,therewasastrong interactionbetweencanopyandunderstorywithgreatestrecruitmentoccurringin locationswherebothhadbeenremoved(p=0.001).thispatternofaugust Pterygophorarecruitmentandastronginteractionbetweenunderstoryandcanopy layersisconsistentwithotherstudiesconductedincentralcalifornia(e.g.,reedet al.1996). Desmarestialigulatahadthegreatestrecruitmentpersquaremeterofany Phaeophyceaeduringthisexperiment,withover50individuals/m 2 insome treatmentsduringjune(figure6).recruitmentwasgreatestduringthejune,and wasgreatestinthescrapedplots(p<0.001,table4).augustrecruitmentdidoccur withinallplots,butrecruitswerenotnearlyasabundantasduringthejune sampling.unlikemacrocystisandnereocystis,desmarestiarecruitmentwas negativelyinfluencedbythepresenceofacanopyinaugust(p=0.021).theeffectof thenewlyformedspringcanopyinjunewaslesscertain(p=0.130). 26

37 )$*+",('-.$+-'/"0+$-1$($+ %! $! #! "! &'()*+,-./0.1)20*3 &'()*+, )20*3 82,+(960(3-./0.1)20*3 82,+(960( )20*3!!"#$ %"&"'( Figure6:DesmarestiarecruitmentatBCMRsampledin2008(mean+/ SE,n=6). Despitehavingfewertotalrecruits,therewasasignificantinteractionbetween canopyandscrapedplotsduringtheaugustsamplingperiod.thisinteractioncan beexplainedbythefactthatthemajorityoftherecruitswereobservedinthe scraped,nocanopy treatment. 27

38 Table1:Split LevelANOVA(TypeIII)ontheeffectsofCanopyandUnderstoryon therecruitmentofnereocystisatbcmr.monthsanalyzedseparately. Date Source df MS FValue P Canopy May Understory <0.001 Canopy*Understory Canopy August Understory <0.001 Canopy*Understory Table2:Split LevelANOVA(TypeIII)ontheeffectsofCanopyandUnderstoryon therecruitmentofmacrocystisatbcmr.monthsanalyzedseparately. Date Source df MS FValue P Canopy May Understory Canopy*Understory Canopy August Understory Canopy*Understory

39 Table3:Split LevelANOVA(TypeIII)ontheeffectsofCanopyandUnderstoryon therecruitmentofpterygophoraatbcmr.monthsanalyzedseparately. Date Source df MS FValue P Canopy May Understory Canopy*Understory Canopy August Understory Canopy*Understory Table4:Split LevelANOVA(TypeIII)ontheeffectsofCanopyandUnderstoryon therecruitmentofdesmarestiaatbcmr.monthsanalyzedseparately. Date Source df MS FValue P Canopy May Understory <0.001 Canopy*Understory Canopy August Understory Canopy*Understory StillwaterCove Priortothisexperiment,theMacrocystispyriferabedatSWCsufferedfrom anabnormallylargeseriesofswellstheproceedingwinter,includingastormevent fromdecember1stthroughdecember4th,2007.thisstormrecordedsustained coastalswellsincentralcaliforniainexcessof30feet(seelewitskyetal.2008for 29

40 partialreview).asaconsequenceofthisstormandtheabnormallyseverewinter, absolutelynomaturemacrocystisplantswerepresentinoraroundtheexperimental plotswhentheexperimentbeganinmarch2008.bymay,macrocystisplantswithin the canopy treatmentshadreachedthesurfaceandbeguntoformacanopy. DuringtheMaysamplingthenumberofMacrocystissporophyteswhichhadreached thecanopywas6.2perplot(0.08/m 2 ).ByJulythatnumberhadincreasedto9.1 individualsperplot(0.12/m 2 ).ThisdensityinJulywasconsistentwiththedensity reportedinmaturemacrocystisbedsintheliterature(daytonetal.1992), suggestingthat,atleastnumerically,themacrocystispopulationatswchad recoveredinabout7months. Overall,thealgalassemblagesatthetwositeswereverydifferent.Excluding thecanopyformingkelps,bcmrwasdominatedbylarge,densepterygophora plantsgrowingaboveavarietyofencrustingspecies.pterygophoradensity measuredduringthefall,2007wassignificantlyloweratswcthanbcmr(2.7 plants/m 2 +/ 0.7SEatSWCvs.9.2plants/m 2 +/ 1.7SEatBCMR,p<0.001). Additionally,PterygophoraplantssampledatSWC(98cmTL,+/ 3.9SE)were significantlyshorterthanthoseatbcmr(152cmtl,+/ 6.5SEatBCMR.t test; p<0.001,n=30) BeneaththePterygophora,themostabundantalgaeweregeniculate corallines,whichcovered66.9%ofallavailablesubstrate(seefigure2).fleshyred algaealsowascommon,with(23.8%ofavailablecover).unlikeatbcmr,wherethe vastmajorityofthesubstratewascoveredbyencrustingcorallinesandsessile 30

41 invertebrates,atswcthesespeciesaccountedforjust8.1%ofallavailablespace. TheremainingalgalcoverwasoccupiedbyDesmarestia(1.9%)andtheperennial fucoidcystoseira(0.08%).geniculatecorallinesandfleshyredalgaecombined accountedforaboutaquarterofthealgaepresent.incontrast,swchadaboutone thirdthedensityofpterygophora,butover90%ofthesubstratewascoveredby eitherfleshyorcalcifiedcorallines. OverallNereocystisrecruitmentwasverylowatSWC,neveraveragingmore than1.3recruits/m 2 duringanyofthemonthssampled(figure7).throughoutall samplingperiods,recruitmentwasonlyobservedinsidethetwoscraped treatments;norecruitmentoccurredinsideplotswheretheunderstoryalgaehad beenleftunmanipulated.thiscompletelackofrecruitmentwithinplotswherethe understoryalgaehadbeenleftintactdemonstratescompetitiveexclusionby understoryalgaeonnereocystisrecruitment.becauserecruitmentonlyoccurred withinscrapedplots,onlythe scraped/canopy and scraped/nocanopy treatmentswereconsideredduringanalysis. 31

42 &"# 605).7389(0)98:.+)09;030) &"! %"# %"! $"# $"! '() *+, -./0 -.1, 20(3 453 Figure7:RecruitmentofNereocystisatSWC(mean+/ SE,n=6).Because Nereocystisrecruitmentwasobservedonlywithintreatmentswheretheunderstory hadbeenremoved,onlythescrapedplotsarecomparedhere. Duringthefallof2009,32ofthesmallplotsatStillwaterCovewereseededwith Nereocystissoritoexaminetheroleofavailablepropagulesonsubsequent recruitment,creatingthefollowingpossibletreatments: seeded/nocanopy, seeded/withcanopy, unseeded/nocanopy and unseeded/withcanopy. An independentt testrunbetweenthetwoseededtreatments(p=0.400)andthetwo unseededtreatments(p=0.283)showednosignificantdifferencebetweenthe canopy and nocanopy treatments,regardlessofwhethertheyhadbeenseeded ornot(table5).aunivariateanovashowednosignificantinteraction(p=0.379, Table6)betweencanopyandseededtreatments.Therefore,toincreasesamplesize whencomparingtheseedingeffect,allseededplotswerepooled,aswereall 32

43 unseededplots,eliminatingthe canopy and nocanopy distinctionswhen comparingtheeffectofseedingplotsonnereocystisrecruitment. ThegreatestnumberofrecruitswereobservedduringMay,withasecond peakofrecruitsinjuly.infiveoutofthesixmonthssampled,plotsthathadbeen seededwithnereocystissorithepreviousyearyieldedmorenereocystisrecruits thanplotsthatreceivednoaddedreproductivematerial.ofthesefive,recruitment wassignificantlygreateratthebeginningofthesurvey,andduringthefinaltwo months.theonlymonthinwhichseededplotsdidnothavegreaterrecruitmentwas duringjune,whichshowedanomalouslylowrecruitmentinbothtreatments,and marginallygreaterrecruitmentintheunseededtreatment. 33

44 &"# 605).7389(0)98:.+)09;030) &"! %"# %"! $"# $"! '() *+, -./0 -.1, 20(3 453 Figure8:RecruitmentofNereocystisatSWCbetweenplotsseededwithadditional zoosporesinfall2007andcontrol( unseeded )plots.thisgraphincludesplots wheretheunderstoryhadnotbeenremoved,eventhoughnorecruitmentoccurred withineitherthe seeded,understory or notseeded,understory treatments (mean+/ SE,n=5). The background levelofnereocystisrecruitmentatstillwatercove(e.g.the recruitmentwhichoccurredinplotsun augmentedbysorithepreviousyear)was alsoanalyzed.forthisanalysisonly un seeded plotswereutilized.becauseno recruitmenteveroccurredinthetwo understory treatments,anindependentsamplesttestwasusedtocomparethetworemainingtreatments: unseeded/with canopy and unseeded/withoutcanopy. Recruitmentwasobservedduringallsix samplingperiods,demonstratingthatnereocystiscanrecruitduringthespring, summerandfallwithoutexternalpropagulesources.despitelowerrecruitment overall,thepatternofrecruitmentwassimilartotherecruitmentofseededplots, 34

45 withtwopeaksofrecruitmentoccurringinmayandagaininjuly(seefigures7& 8).Oncetheseededplotsweretakenoutofthemodel,theroleoftheMacrocystis canopybecameapparent.duringthefirsttwomonthsthecanopyhadno discernibleeffectonnereocystisrecruitmentatswc.however,everymonthfrom JuneonwardhadsignificantlygreaterNereocystisrecruitmentwithinthe no canopy treatment,withnorecruitmentoccurringinthecanopytreatmentduring thefinaltwomonthsofsampling(table6). RecruitmentofMacrocystispyriferainSWCwashigherthanNereocystis luetkeanaduringallmonthssampled(figures7&9),withrecruitmentshowingtwo peaks,thefirstinmayandthesecondinjuly. ( :;*2+;:<0-+2;=252+ ' & % $ # "! "#$%&'()*+,*-%.,&/ "#$%&'()*0123*-%.,&/ 4.('$52,$/)*+,*-%.,&/ 4.('$52,$/)*0123*-%.,&/!!!!!! )*+,-. /012 /03. 42*5 675 Figure9:RecruitmentofMacrocystisatSWCin2008(mean+/ SE,n=6) 35

46 Duringallmonthssampled,the scraped/nocanopy plotsshowedthegreatest recruitment,and understory/canopy treatmentshadeitherthelowest recruitmentorwerenotsignificantlydifferentthanthelowesttreatmentforthat month(table7a).becauserecruitmentwasnotobservedinsome month/treatmentcombinations,certainmonthswereanalyzedusingaone way ANOVA(Table7b).Aprilshowedthelowestrecruitmentoverall,withnosignificant differencebetweenanyofthetreatments.recruitmentofmacrocystisincreased aboutanorderofmagnitudeinmay,withsignificantlygreaterrecruitmentwithin thescrapedplots.thecanopyclearingsshowednosignificantdifferencecompared tocontrolsduringthemonthofmay.juneshowedamarkeddecreaseinoverall recruitment.the scraped/nocanopy treatmenthadsignificantlygreater recruitmentthanalltheothertreatments,howevertheremainingtreatmentswere notsignificantlydistinctfromoneanother,andonlyasinglerecruitwasobservedin anyoftheseothertreatmentsinjune(n=45).julyshowedasecondspikein Macrocystisrecruitment,withthe scraped/nocanopy plotsagainshowingthe greatestrecruitment.boththescrapedandcanopytreatmentsweresignificant alongwithaninteractionbetweenthesefactors.julywastheonlymonthsampled whereeachtreatmentwassignificantlydifferentfromtheothers.recruitmentwas significantlygreaterinthe scraped/nocanopy treatmentthaninthethreeother treatments,whichwerenotstatisticallydistinguishablefromeachotherand showeddecreasedrecruitmentrelativetothepreviousmonth.recruitment continuedthroughoctober,andfollowedapatternverysimilartoseptember. 36

47 ThefirstrecruitsofPterygophoracalifornicawerenotobservedinStillwater CoveuntilMay,andrecruitmentwasdominatedbyasinglelargeeventduringthe monthofjuly(figure10).thefourrecruitsobservedduringthemaysampling wereallwithinthe scraped/nocanopy treatmentand,curiously,wereallfoundin thesamesingleplot.despitethelowstatisticalcertaintyofthesefourclustered recruits,themaysamplingshowsasimilarpatternseeninsubsequentmonths,with the scraped/nocanopy treatmentreceivingthebulkofnewpterygophorarecruits. &"! 605).7389(0)98:.+)09;030) &!! %! $! #! "!! '() *+, -./0 -.1, 20(3 453 Figure10:PterygophorarecruitmentatSWCin2008(mean+/ SE,n=6) Infact,duringJuneandOctoberthe scraped/nocanopy treatmentshave significantlygreaterrecruitmentthantheotherthreetreatments,andtheremaining threetreatmentsarenotsignificantlydifferentfromeachother(table8a). PterygophorarecruitmentinJulywassignificantlygreaterinscrapedplots,butwas 37