Abstracts IAP preliminary version · 16:00 W.-WOZNIAK DEVERCELLI ZNACHOR IZAGUIRRE Discussion 16:30 SELMECZY O'FARRELL BI OLRIK Session 17:00 Discussion Discussion Discussion Discussion

18th WORKSHOP OF THE INTERNATIONAL ASSOCIATION

OF PHYTOPLANKTON TAXONOMY AND ECOLOGY (IAP)

Natal, Rio Grande do Norte – Brazil August 27 - September 3, 2017

ABSTRACT BOOK

18th WORKSHOP OF THE INTERNATIONAL ASSOCIATION OF PHYTOPLANKTON TAXONOMY AND ECOLOGY (IAP)

Natal, Rio Grande do Norte – Brazil, August 27 - September 3, 2017

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18th IAP SCHEDULE SUNDAY MONDAY TUESDAY WEDNESDAY THURSDAY FRIDAY SATURDAY SUNDAY 27/ago 28/ago 29/ago 30/ago 31/ago 01/set 02/set 03/set

08:30 CALADO SARMENTO/ UNREIN

Field trip

MENEZES ZOHARY Microscope KRUK

Farewell Departure

09:00 09:30 10:00 Cofee Break Cofee Break Cofee Break Cofee Break Cofee Break 10:30 ZUTINIC -

Microscope session

Microscope session

QUESADO 11:00 PICCINI N.-FLORES MUHL 11:30 HUSZAR CARDOSO BORICS 12:00 12:30 13:00 13:30 14:00 Lunch & Beach Lunch & Beach 14:30

REGISTRATION

15:00 15:30 CAGLE COSTA DESCY GER 16:00 W.-WOZNIAK DEVERCELLI ZNACHOR IZAGUIRRE Discussion 16:30 SELMECZY O'FARRELL BI OLRIK Session 17:00 Discussion Discussion Discussion Discussion 17:30 Welcome Cofee Break Cofee Break Cofee Break Cofee Break Cofee Break 18:00 cocktail dinner

POSTERS POSTERS Microscope

session Microscope session

Closing act 18:30 19:00 Dinner Dinner 19:30 20:00 Dinner Dinner Dinner Dinner



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18thIAPABSTRACTS

PLENARY LECTURES

MONDAY28/08

Heterotrophyandmixotrophyinfreshwaterdinoflagellates:underlyingmechanismsandphylogeny

AntónioJoséCaladoDepartmentofBiology,GeoBioTecResearchUnit,UniversityofAveiro,Portugal.Heterotrophicdinoflagellatesconsumefoodparticles inanumberofdifferentways.Someofthese feeding mechanisms are associated with particular cell features that can usually berecognizedbyTEMexaminationofserial-sectionedcells. Inaddition,cellsthatarefeedingorattemptingtofeedoftendisplayrecognizablebehaviors.Someofthefeaturesassociatedwithfood uptake mechanisms seem to be plesiomorphic whereas others display a much morerestricted distribution and appear to be more recent. The presence in many phototrophicdinoflagellates of features that have been firmly associated with food uptake in severalheterotrophicspecies leadsfrequentlytotheassumptionthatthesechloroplast-bearingcellsaremixotrophic. However, food uptake in phototrophic species has been demonstrated forvery few freshwater dinoflagellates. The first 200 years of dinoflagellate classification weredominatedbyasetof‘obvious’characters,suchastheexistenceofacingulumanditspathonthecellsurface,orofwell-definedplatesandtheirarrangement.Ourcurrentunderstandingofdinoflagellate phylogeny is largely based on molecular markers and reveals importantmismatches between the distribution of classical features and evolutionary units. Mapping‘new’ characters, including feeding mechanisms and related structures, onto the emergingphylogeneticschemeisthecurrentchallenge.



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TUESDAY29/08

Interactionstrengthinplanktonicsystems:Whatcanwelearnfromlatitudinalgradients?

HugoSarmentoLaboratoryofMicrobialProcessesandBiodiversity,DepartmentofHidrobiology,UniversidadeFederaldeSãoCarlos,BrazilBiotic interactions are fundamental processes in planktonic community dynamics. Inthispresentation,Iwillreviewtheoreticalconceptsonbioticinteractions,methodstoquantify interaction strength and specialization in interaction networks. I will alsoexplore ecological theories on biotic interactions and some examples of empiricalstudies.Studyingaquaticecosystemsfromcontrastinglatitudesprovidesanexcellentopportunity to understand the structure and functioning of planktonic interactionnetworks. A number of studies have shown that tropical lakes are different fromtemperate ones in some fundamental ways. Constantly high temperature andradiationhavestrongconsequencesforstratificationandbiologicalprocesses.Besides,omnivory iswidespread in tropical foodwebs and long periods of fish reproductionenhance predation pressure on zooplankton and constrain community compositionandbodysize,affectingallcompartmentsofthefoodweb.Lowabundanceorabsenceoflargecladoceransintropicallakesdeterminesaparticularconfigurationofthefoodweb.Itishighlyprobablethatbioticinteractionshaveconsistentlatitudinalvariationsthat might affect the structure and functioning of planktonic interaction networks.However, theobservationsof suchpatternsareonly starting tobeunveiled.Ahugeamount of work is still to be done in aquatic systems distributed along latitudinalgradients in large scales, in order to cover all nodes and interactions of planktonicnetworks.

Acknowledgements:FAPESP(process2014/14139-3)



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TUESDAY29/08

BacterivorybymixotrophicphytoflagellatesFernandoUnrein1&MarinaGerea21InstitutodeInvestigacionesBiotecnológicas-InstitutoTecnológicodeChascomús(IIB-INTECH),UNSAM-CONICET,Argentina2LaboratoriodeFotobiología,INIBIOMA(UNComahue-CONICET),ArgentinaMixotrophyinalgae,definedasthecombinationofphagotrophyandphototrophyinasinglecell, is widespread among most algal groups containing flagellated species. Mixotrophicflagellatesvarywidelyintheiringestioncapabilityandresponsetoabioticconditions.Weusedliteraturedata to review theecological strategyand impactonbacterioplanktonofdifferentmixotrophic algal groups: Chrysophyceae (Dinobryon and Ochromonas-like species),Dictyochophyceae (Pseudopedinella), Haptophyceae (Prymnesium, Chrysochromulina),Cryptophyceae (Cryptomonas, Plagioselmis) and Dinoflagellates. Some information aboutmixotrophy in Raphidophyceae and Prasinophyceae are also available. We extractedinformationfromabout50articles,includingmarineandfreshwatersystems,resultinginmorethan600measurementofgrazingratesfromnaturalphytoplanktoncommunities.Inaddition,we summarised results of experiments performed with isolated strains. We will discussqualitative and quantitative differences in the use of phagotrophy among dominantphytoflagellates.



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THURSDAY31/08

Taxonomicupdatinginmixotrophicphytoflagellatesofinlandwaters:cryptophytesandeuglenophytesascasestudies

MariângelaMenezesDepartamentofBotany,MuseuNacional,UniversidadeFederaldoRiodeJaneiro,BrazilPhytoflagellates substantially contribute to theabundance,biomass,andprimaryproductioninfreshwaterwaters,butinformationonthetruedistributionofspecificgroupsisstillscarce.Oneof themain reasons for this knowledge gap lies in the fewmorphological features andreduced dimensions that these organisms generally present.Until recently, our taxonomicalknowledgeofthisbiologicalgroupwasbasedonlyonmorphologicaltraits.Overthetwolastdecades molecular studies carried out particularly for marine environments have revealedseparateornovellineagesaswellahithertounknowncrypticdiversityofseveralmixotrophicphytoflagellates phyla. In contrast, until very recently, only a few molecular studies haveevaluated their biodiversity in freshwater systems. The present discussion summarizes thecurrent taxonomictreatmentofmixotrophicphytoflagellates in freshwatersystems, focusingonthereassessmentofgeneraandspeciesofcryptophytesandeuglenophytes.



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SATURDAY02/09

Atrait-basedapproachtophytoplankton-zooplanktoninteractions

CarlaKruk1,2,MaiteColina2,GissellLacerot1,CarmelaCarballo2,ClaudiaPiccini3,AngelM.Segura41EcologíaFuncionaldeSistemasAcuáticos,CURE-Rocha,UniversidaddelaRepública,Uruguay.2SecciónLimnología,IECA,FacultaddeCiencias,UniversidaddelaRepública,Uruguay.3Departamento de Microbiología, Instituto de Investigaciones Biológicas Clemente Estable,MEC,Uruguay.4Modelización y Análisis de Recursos Naturales, CURE-Rocha, Universidad de la República,Uruguay.Trait-basedapproachesareahelpfulapproximationtosummarizeecologicalprocesses.Withtheaimofexplainingphytoplankton-zooplanktonalongenvironmentalgradientswecombinedtheanalysisoftraitsatdifferentorganizationlevels(usingabundanceweightedaverages)andtheclusteringofspeciesintofunctionalgroups.Phytoplanktonwasclusteredintomorphology-based functional groups (MBFG) and herbivorous zooplankton into broad taxonomic groups(i.e.calanoidcopepods).Basedonaliteraturereviewofspecificclearanceandingestionrateswe characterized zooplankton grazing potential on phytoplankton from freshwaters. BothRotifersandCladoceranhadpoor foodselectivityandagreaterpotentialgrazinguponsmalland medium-sized species (MBFG I and IV) with Type III and Type II trait-based functionalresponsesrespectively.CopepodsconsumeddifferentMBFGs.ATypeIIpatternwasobservedwhen feeding on MBFGs V and VI. We then evaluated the applicability of these results tonaturalcommunitiesandestimatedtheroleofherbivoryinexplainingcommunitiesstructurealongtwobroadenvironmentalgradients.Using83freshwatershallowlakessampledfromtheEquator to Patagonia in South Americawe found increasing clearance rates towards colderregions due to higher biomass of Cladoceran, with feeding preferences forMBFG IV and I.Further,herbivorywasselectedalongwithtemperatureasthemaindrivingforcesofplanktoncommunity richnessalong the latitudinalgradient.Then,weanalyzedseasonal samplesover800km,fromaneutrophicfreshwaterreservoirinUruguayriver,tomarinewaterintheouterlimitofRíodelaPlataestuary.Herewefoundthatsalinitywasakeyenvironmentalvariableaffectingcommunitystructureandmodulatingtrophic interactions.Thecombinationoftrait-based approaches with phylogenetic affinities, particularly in the case of zooplankton, washelpfulinexplainingplanktoninteractionsindifferentenvironmentalgradients.



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18th IAP ABSTRACTS

ORAL PRESENTATION (chronologicorder,seeschedulepag.2)

Bacterial-phytoplanktoninterfaceinnaturallakeecosystems

PetarŽutinić1,SandiOrlić2,PetraPjevac3,AnđelkaPlenković-Moraj1,KoraljkaKraljBorojević4,Zrinka Ljubešić1, Sunčica Bosak1, Maja Šimunović5, Igor Stanković6, Filip Stević7, DubravkaŠpoljarićMaronić7,TanjaŽunaPfeiffer7,GordanaGoreta8,GáborBorics9,GáborVárbíró9,AnitaVucić10,IvančicaTernjej1,MarijaGligoraUdovič1

1DepartmentofBiology,FacultyofScience,UniversityofZagreb,Croatia.E-mail:2RuđerBoškovićInstitute,Croatia.3DepartmentofMicrobiologyandEcosystemScience,DivisionofMicrobialEcology,UniversityofVienna,Austria.4MinnesotaDrive,GreatSankey,Warrington,WA53SY,UnitedKingdom.5Hrvatskaagencijazaokolišiprirodu,Croatia.6Hrvatskevode,CentralWaterManagementLaboratory,Croatia.7DepartmentofBiology,JosipJurajStrossmayerUniversityofOsijek,Croatia.8PublicInstitution`NationalParkKrka`,Croatia.9DepartmentofTiszaRiverResearch,MTACentreforEcologicalResearch,Hungary.10Department of Environmental Protection and Health Ecology, Institute of Public HealthZadar,Croatia.Cryptophytes,chrysophytesanddinoflagellatesaregroupsofphytoplanktonlargelyconsistingof species with well documented mixotrophy. These groups also comprise a major part ofphytoplankton biomass in karstic lakes with good to high ecological status. The aim of thestudywastoestablishthelinkbetweenbacterialcommunityandpotentialmixotrophsintheplanktoniccommunityofakarsticmesotrophicVisovacLake (KrkaNationalPark,Croatia), inorder toprovideapreciseassessmentof theecological statusof lakeecosystem. Integratedvertical samples for phytoplankton, samples for physical-chemical parameters, waterchemistryanalysesandbacteriologyweretakensimultaneouslyfromthedeepestpointofthelake, once a month in the period between April and September 2016. Phytoplanktoncomposition andbiomassweredeterminedby standardmethods,while fluorescence in situhybridization with signal amplification and catalyzed reporter deposition (CARD-FISH) wasappliedforbacterialmicroscopicquantification.Additionally,filteredwaterwasusedforDNAextraction and 16S rRNA gene sequencing for bacterial identification. Total phytoplanktonbiomass varied from 0.24 mgL-1 (June) to 0.75 mgL-1 (July). Potentially mixotrophic speciescharacterizing the community were: Dinobryon divergens, Dinobryon bavaricum, Dinobryoncrenulatum,Chromulina sp.,Ochromonas danica,Plagioselmis nannoplanctica,Cryptomonassp., Parvodinium inconspicuum and Ceratium hirundinella. The lowest total bacterialabundancewasdeterminedinApril(2.61x106cellmL-1),whilstthehighestwasinJuly(11.39x106 cellmL-1). Sequencing of 6 integrated samples resulted in a total of 132 429 nucleotidesequences, with 5 bacterial groups identified: Betaproteobacteria, Actinobacteria,Bacterioidetes,ChloroflexiandVeruccomicrobia.Actinobacteriawasthemostabundantclassinall investigatedmonths(avg.34%),whileBetaproteobacteriawassubdominant(avg.22%).Multivariate analysis provided a statistically significant correlation between the selectedphytoplanktonspeciesanddeterminedbacterialgroups.Theresultswillbeusedtodeterminerelation betweenmixotrophic species and bacterial groups in lakes with variable ecologicalstatus.



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Livingtogether:theheterotrophicbacterialcommunityassociatedtoMicrocystisspp.blooms

Claudia Piccini1, Eliana Nervi1, Alvaro González1,2, José Sotelo-Silveira2, GabrielaMartínezdelaEscalera1,AngelSegura3,CarlaKruk41Departamento de Microbiología. Instituto de Investigaciones Biológicas Clemente Estable,Uruguay.2Departamento de Genómica. Instituto de Investigaciones Biológicas Clemente Estable,Uruguay.3Modelización y Análisis de Recursos Naturales. Centro Universitario Regional Este-Rocha,Uruguay.4EcologíaFuncionaldeSistemasAcuáticos.CentroUniversitarioRegionalEste-Rocha,Uruguay.During the last years, the knowledgeabout thebiologyandecologyof toxic, bloom-formingcyanobacteriahas increased, including information about the interactionsbetweendifferentcyanobacterialspeciesandbetweencyanobacteriaandzooplankton.However,littleisknownabouttheinteractionsbetweencyanobacteriaandtheheterotrophicbacteriathatliveincloseassociation,suchasthoseembeddedintheexopolysaccharidematrix(mucilage)surroundingthecoloniesofMicrocystisspecies.Owingtoitschemicalstructure,themucilageconstitutesarichcarbonsource for theassociatedheterotrophicbacterial communityand,as ithasbeenshowndifferentspeciescanproducemucilagewithdifferentcomposition.Thus, it shouldbeexpectedthatheterotrophicbacterialcommunitydevelopedwhenthemucilageavailabilityishigh (e.g. during blooms)would be enriched in taxa harbouring enzymes for polysaccharideand microcystins degradation. Furthermore, the interaction between the heterotrophicassociated community and Microcystis could play a functional role in the biology andpopulationdevelopmentofthecyanobacterium.Inthiscontext,wecomparedthestructureofthe heterotrophic bacterial community in presence and absence ofMicrocystis blooms insamples from Río Uruguay and Río de la Plata. Bacterial community composition wasaddressedby16SrRNAampliconsequencing(V3-V4region).Inaddition,functionalcapabilitiesofthecommunitieswerepredictedusingasoftwarepackage.Findingsaboutthestructureandfunction of bacterial communities associated to Microcystis species through the assessedecosystemswillbeshownanddiscussed.



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CarbonpartitioninginplanktoniccommunitiesinanAmazonianfloodplainlake:

classicalchainvs.microbialfoodweb.Ivan Brito Feitosa1, Carolina D. Domingues2, Hugo Sarmento3, Eleonora Appel,WanderleyRodriguesBastos1,VeraL.M.Huszar21LaboratóriodeBiogeoquímicaAmbiental,FundaçãoUniversidadeFederaldeRondônia,Brazil.2LaboratóriodeFicologia,MuseuNacionaldaUniversidadeFederaldoRiodeJaneiro,Brazil.3DepartamentodeHidrobiologia,UniversidadeFederaldeSãoCarlos,Brazil.Planktoniccommunitieshavebeenanalyzedaccordingtoclassicalchain(CC)-phytoplankton,zooplankton, fish -butpelagicenvironmentshavealsobacteriaandprotozoa- themicrobialfood web (MFW). Trophic interaction throughMFW has been pointed as more relevant intropicalthanintemperateregions.Here,wehypothesizeahigherrelevanceofMFWthanCCinanAmazonian floodplain lake.Weestimatedpartitioningcarbon inplanktoncommunitiesandanalyzedthe interactionamongplanktonfractions,basedoncarboncontentandabioticconditions. We sampled an Amazonian floodplain lake connected to Madeira river in 10sampling stations during low (LW) and high water (HW). We estimated carbon in theplanktonic biota (C-biota): heterotrophic bacteria (HB); autotrophic picoplankton (APP);protozooplankton as heterotrophic nanoflagellates (HNF) and ciliates (CIL); phytoplankton(PHY) and metazooplankton (ZOO). We analyzed climatological, hydrological, physical andchemicalvariables,includingtotalanddissolvednitrogen,phosphorusandcarbon.Interactionswereevaluated throughsimpleandmultiple regressions.C-biota (171.9 to546.1µgC/L)washigherduringLW(PHY+CIL)thaninHW(HB).Inbothperiods,HNFandZOOshowedthelowestcarbon stocks. Trophic interaction indicated ZOO as potentially controlled by PHY, which inturn was regulated by light. Despite non-significant relationships between PHY andorthophosphate,theconcentrationsbelow10µgP/LindicatedPcontrolduringLW.HNFcanbethoughtascontrolledbyCIL,andthisbyHBandAPP.HBincreasedwithDOCandoccurredinclearerandlowN-enrichedwaters.CILweredependentonsmall-sizePHYandoccurredinlowTPconcentrations.Asexpected,APPwasmoreabundantinlowTNandTPlevels.MFWandCCoccurredinsimilarbiomassduringLW,butMFWwasdominantduringHW.Inconclusion,ourhypothesiswaspartiallyverified,withhigherimportanceinbiomassoftheMFWinHW,whichwassharedwithCCduringLW.



11

Effectofcompounddisturbance,salinificationandinvasionofatoxicand

mixotrophicalga,onlakeplanktoncommunitiesSierraE.Cagle1,DanielL.Roelke1,RikaM.W.Muhl11DepartmentofWildlifeandFisheriesSciences,TexasA&MUniversity,USA.Aquaticecosystems today facea risingnumberof threatsdue largely toclimatechangeandother anthropogenic disturbances, which include increased salinity levels and spread ofinvasive species. In some areas of the U.S., e.g. southcentral region, changes to freshwatersalinity levels are occurring because of decreased inflows caused by drought andimpoundments,aswellasbrinedischargesfromdesalinationplants.InnorthernareasoftheU.S., salinification comes about through road salting. Additionally, a toxic and mixotrophicalga,Prymnesiumparvum, has invaded throughout the southcentralU.S., forming fish-killingbloomsinmanyreservoirs.ResultsfrompreviousmonitoringstudiesconductedinTexashaveshown that bloom occurrence in some systems is linked to site specific salinity thresholds,wherebloomscanonlyoccurinasystemoncesalinityisaboveacriticallevel.IntheseTexasreservoirs, specifically those of the Brazos River Basin, where a natural salinity gradient isformed by a salt rich geologic formation in the basin’s upstream region, it is likely that theplanktoncommunitiesofdifferentreservoirsaredifferentlyadaptedtocopewithsaltloadingevents. It may be that plankton communities adapted to natural salt-loadings are moreresistant to salt-loading disturbances, thus beingmore resistant to P. parvum invasions. Toexplorethisnotion,weconductedin-fieldmesocosmexperimentsusingplanktoncommunitiesfromtworeservoirswithdifferenthistoriesofsalinityfluctuationthatfocusedontheimpactsofcompounddisturbances,salinification,andP.parvuminvasion.WeobservedsimilarimpactsofP.parvuminvasionbetweenlakes,whereasignificantincreaseincelldensityoccurredonlywhen salt was added and grazers were removed. Furthermore, because ambient salinityconditionsinLakePossumKingdomweresimilartothoseofLakeWhitneywithsaltadded,itappearsthattheresidentassemblageofLakePossumKingdomismoreresistanttoP.parvuminvasion.



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Extremedroughtenhancesmixotrophicorganismsintropicalsemi-aridreservoirs

Mariana R. A. Costa1, Rosemberg F. Menezes2,5, Hugo Sarmento3, José L. Attayde2,LeoneldaS.L.Sternberg6&VanessaBecker1,41Programa de Pós-Graduação em Ecologia, Universidade Federal do Rio Grande do Norte,Brazil.2DepartamentodeEcologia,UniversidadeFederaldoRioGrandedoNorte,Brazil.3DepartamentodeHidrobiologia,UniversidadeFederaldeSãoCarlos,Brazil.4DepartamentodeEngenhariaCivil,UniversidadeFederaldoRioGrandedoNorte,Brazil.5DepartamentodeFitotecniaeCiênciasAmbientais,UniversidadeFederaldaParaíba,Brazil.6DepartmentofBiology,UniversityofMiami,CoralGables,Florida,USA.Climate change is affecting the global hydrological cycle leading to drastic changes infreshwaterhydrologicalregimeduetorainfallreduction,especiallyinsemi-aridregions.Waterlevel fluctuations alter water physical and chemical properties, which are key drivers ofchangesinphytoplanktoncommunitystructureanddynamics.Ourmainhypothesisisthatthewater level reduction will increase nutrients concentration favoring the dominance ofcyanobacteriaatdryconditions,butatextremelydryconditions(i.e.withextremelylowwaterlevel)mixotrophicalgaeshouldthrive.Totestourhypothesis,weusedacomparativeanalysisofecosystemsinaspace-for-timesubstitutionapproachtopredicttheconsequencesofwaterlevel reductiononphytoplanktonfunctional traitsandwaterqualityvariables.Wecomparedthese variables between two sets of reservoirs (n=16) located in two watersheds withcontrastingprecipitationregimeswithintheBraziliansemi-aridregion:eightintheSeridóRiverBasin(SB)andeightinthePiancóRiverBasin(PB),withannualmeanprecipitationaround500and700mm,respectively.Thetwosetsof reservoirswerecompared inadryperiodandanextremelydryperiodtoevaluatetheresponseofthevariablestoanextremeclimaticevent.The results showed that drought intensification (rainfall reduction) reduces the reservoirswaterlevel,euphoticzoneandinlet:evaporationratio(proxyforwaterbalance),andincreasestotal phosphorous and conductivity. At the dry period with higher water level, colonialcyanobacteria dominated, while at the extremely dry period with lower water level, thecontribution of mixotrophic algae increased. Hence, results showed that during extremedrought events mixotrophic phytoplankton functional traits should prevail instead traitsrelevanttocyanobacteriaspecies(i.eNfixing,coloniesandfilaments).Therefore,wemayinferthatthescenarioobserved inthedrierregion(SB)duringextremelydryperiodmightbethefutureforothersemiaridaquaticecosystemsaffectedbyclimatechanges.



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EffectofphytoplanktonassemblagesonthezooplanktonpopulationinLakeStechlin

BalázsGézaSelmeczy1,PeterKasprzak2,AndrásAbonyi3,PeterCasper2,JuditPadisák1,41DepartmentofLimnology,UniversityofPannonia,Hungary.2Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and InlandFisheries,Germany3MTACentreforEcologicalResearch,DanubeResearchInstitute,Hungary4MTA-PELimnoecologyResearchGroup,HungaryLakeStechlinisanoriginallydeep,dimictic,oligotrophiclakeanditsplanktoncommunitywasinvestigatedfromthe1950s.However, regularmonitoring isperformedonly from1994.Ouraimwas to investigate the phytoplankton and zooplankton relationship based on the long-termmonitoringdataandinshort-termexperimentstargetedonexploringeffectsofclimatechangeand itsscenariosperformed in largesizedmesocosms in thesouthbasinof the lake.During the last20years, signalsofeutrophicationwereobservedboth in thephytoplanktonand zooplankton, such as the increasing dominance of filamentous cyanobacteria(Aphanizomenon flos-aquae,Dolichospermum species) in the summer assemblages and thedecreasingamountoflargesizedzooplanktonspecies(e.g.Eurytemoralacustris,Eudiaptomusgracilis). According to the indication of the results, before the year 2000 the biomass ofzooplankton population was inversely proportional to the standing crop of Planktothrixrubescens. However, in the recent years the zooplankton community was apparently notaffectedbythesummerbloomoffilamentouscyanobacteria.Thephenomenonisnotclarified,but possibly caused by the slightly increased amount of cryptophytes or by the alteredcompositionofzooplanktoncommunity.



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MixotrophicphytoplanktondynamicsinshallowMediterraneanwaterbodies:how

tomakeavirtueoutofnecessity

LuigiNaselli-Flores1&RossellaBarone11DepartmentofBiological,ChemicalandPharmaceuticalSciencesandTechnologies,SectionofBotanyandPlantEcology,UniversityofPalermo,Italy.Mixotrophy is a combination of photosynthesis and direct access to organic carbon sourcesthroughosmotrophyorphagotrophy.Thisstrategyiscommonlyoccurringinmarine,brackish,andfreshwaterecosystemsandhasbeenputinrelationtobothscarcityofinorganicnutrientsand poor light conditions. However, in a Sicilian pond we observed cyclic blooms ofmixotrophic planktonic algae belonging to the classes Haptophyceae and Cryptophyceae indifferent periods during winter, and under high resources (both light and nutrients)availability.Theanalysisofa10-yearrecordofphytoplanktondatafromaSicilianshallowlakeallowed us to hypothesize that fluctuating conditions in resource quantities may fuel thegrowth, and eventually lead to the blooming of the haptophyte Prymnesium parvum.Conversely, it was not possible to find clear environmental patterns to explain speciesdominance and growth patterns of the cryptomonads inhabiting the lake but zooplanktongrazing.Differenttaxonomicgroupscanthereforereceivedifferentbenefits,servingavarietyofpurposes,frommixotrophyasitmaybeexpectedfromthedifferentevolutionarypathwaysthathaveledtothisfeedingbehavior.



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Phytoplankton,periphytonandzooplanktoninteractionsinthepelagicandlittoral

regionsofalargesubtropicalshallowsubtropicallake

LucianadeSouzaCardoso1,DeniseMatiasFaria1,LucianedeOliveiraCrossetti1&DaviddaMottaMarques21DepartamentodeBotânica,UniversidadeFederaldoRioGrandedoSul,Brazil.2DepartamentodeObrasHidráulicas,UniversidadeFederaldoRioGrandedoSul,Brazil.Many are the food sources for the zooplankton of heterogeneous and highly hydrodynamicshallowlakes.Inthissense,theobjectiveofthisstudywastounderstandifthespatial(pelagicand littoral zones) and temporal (in a short time scale) variation of the phytoplankton andperiphytic communities could influence the zooplankton community structure in a largeshallow polymictic lake (Mangueira Lake, southern Brazil).Water sampleswere gathered atintervalsof3,5and15days,for60daysduringsummerof2012,forphysical,chemical,andbiological analyzes (abundance and maximum linear dimension of subsurface zooplankton,phytoplanktonandglass slide-colonizedperiphyton installed inboth lake regions.A summerstorm (wind velocity 29.5m s-1, precipitation 47mm) in the 20th day disturbed periphytonsuccession in both litoral and pelagic zones, meanwhile the respective responses ofphytoplanktonandzooplanktonwereonlyregisteredonthepelagiczoneonthe25thto30thdays, presenting higher succession rates. The results showed that the phytoplankton sizestructure varied between pelagic and littoral zones, being significantly controlled by theabundance of zooplankton size classes (F =12.7, p = 0.001), regardless the successionalvariability (p<0.05). Although the periphyton did not influence the phytoplankton, bothcommunitiesvariedpositively (p=0.008).Zooplanktonsizestructurevariabilitywasexplainedmore by the periphyton than by phytoplankton size structure. However, the zooplanktonseemed to have grazed both algae communities, selecting rather small to medium sizedphytoplankton (<50µm),whichwasdominatedbycolonial cyanobacteria, speciallyafter thedisruptionofperiphytonaftertheregisteredstorm.TheseresultsevidencedthatthebiologicalinteractionsbetweenthosecommunitiesaredynamicandcloselyrelatedtotheenvironmentalvariabilityinMangueiraLake.



16

3xC!Competition,CooperationorCoexistence–doweunderstandtrophicnetworksinplanktonofsmallandshallowreservoirs?

ElżbietaWilk-Woźniak1,JoannaKosiba1,WojciechKrztoń1,EdwardWalusiak1,DamianChmura21InstituteofNatureConservation,PolishAcademyofSciences,Poland.2InstituteofEnvironmentalProtectionandEngineering,UniversityofBielsko-Biala,PolandUnderstandingofaquaticmicrobialecology,particularlytheinteractionsintrophicnetworks,isstill far fromsufficient.Researches includingbiotic interactionsbetweenmicroorganismsareespeciallyneededforshallow,smallreservoirsbecausetheyareoneofthemostendangeredlandscape elements, which disappear due to human impact. Such reservoirs are importanthabitatsandrefugesfororganisms,andbiodiversityhotspots.Theyplayan importantrole inmaintaining gene pools and deliver ecosystem services. Thirty years ago, the PEG modelexplained the role of abiotic and biotic factors as significant drivers of phytoplankton andzooplanktondevelopment in lakes, and recently thatmodelhasbeenextendedby includingciliates. Beside ciliates,mixotrophic algae are other group, which functions and relations infreshwatersarepoorlyrecognized.Theaimofourstudieswastofindouthowthreetypesofmicroorganisms: ciliates,mixotrophic algae andmetazooplankton are related to each other.We sampled 6 shallow reservoirs fromMay to October. To describe relationships betweenmentioned groups we applied canonical analyses. Analysis indicated relationships betweenmixotrophic algae (euglenoids, dinoflagellates), omnivorous ciliate, omnivorousmetazooplankton, and predators, and others. The strongest relations (regression model,R2=0.56)wasindicatedforciliatesfeedonalgaeandomnivorousciliates.Interestingnegativerelations (weak) was found for dinoflagellates and metazooplankton predators. In ourpresentationwewouldliketodiscussdifferentpossibilitiesofcommonlifeofmicroorganismswhich can share the same type of food, eat each other or avoid themselves: do theycooperate,competeorsimplycoexist?



17

Microbialmetacommunityassemblyandinteractionnetworksinfloodplainlakes

MelinaDevercelli1,SebastiánMetz2,FernandoUnrein2,PabloScarabotti1,3,VanesaDiPasquale3, Florencia Rojas Molina1,4, Juan César Paggi1, Patricio Alvarenga1, GiselaMayora1, Gastón Chingolani4, Berenice Schneider1, Federico Giri1,3, MercedesMarchese1,31InstitutoNacionaldeLimnologia,CONICET,UniversidadNacionaldelLitoral,Argentina.2InstitutodeInvestigacionesBiotecnológicas,InstitutoTecnológicodeChascomús,(IIB-INTECH–CONICET),UniversidadNacionaldeSanMartín,Argentina.3FacultaddeHumanidadesyCiencias,UniversidadNacionaldelLitoral,Argentina.4FacultaddeBioquímicayCienciasBiológicas,UniversidadNacionaldelLitoral,Argentina.Theplanktonicmicroorganismsoffloodplainlakesconstituteacomplexassemblageforwhichmetacommunity framework emerges as appropriate to unveil their diversity and assembly.Thebeautyofthisapproachisthatitassumestheinfluenceofenvironmentalfilterswithintheinterconnecteddynamicoflocalcommunities.Besidesenvironmentalconditions,microbesareintegratedininteractionnetworksthatinturn,areinfluencedbyspatialfactorsthatdampenthedestabilizingoscillationsofstrongassociations.Withinthis frame,weaimtoglimpsetheassemblyofmicrobial community in floodplain lakes.Weanalyze the relative importanceofenvironmental and spatial factors, and interactions, and if spatial dynamic (by means ofenvironmental connectivity) affects community attributes and interactions strength. Wesampled connected and disconnected lakes (n=14) during drought and flood periods(November 2013, September 2015). We quantified bacterioplankton, picocyanobacteria,picoeukariotes, heterotrophic and autotrophic nanoflagellates (flow cytometer,epifluorescencemicroscope),andphytoplankton>8µm(invertedmicroscope).Wemeasuredspatial, physical, chemical, and morphometric variables of lakes, as well as macrophytes,zooplankton and planktivorous fish composition and abundances. To characterize andcompare microbial structure among connected/disconnected lakes, and drought/floodperiods,weperformedPERMANOVAandSIMPERanalyses.Weappliedmantel correlogramsand pRDA to dissect the relationships among spatial, environmental, and biological factorsdrivingthedifferentmicrobialassemblages.Weperformedco-occurrenceanalysestospeciesandtrophicfunctionalgroupstoapproximatebiologicalinteractions.Weusedpathanalysistotestthefitofdifferentinteractionmodels.Withthiswork,weexpecttoincorporatetheeffectofspeciesinteractionsandtheroleofspatialdynamicinnetworkstothecurrenthypothesesofmicrobialassembly.Wediscussdifferencesinthedrivingfactorsforeachassemblage(fromthe smallest heterotrophic bacterioplankton to the largest autotrophic phytoplankton). Wehypothesize that connectivitymaintains thehigh floodplaindiversitydue to recruitmentandexchangeoforganismsamongenvironments,andbydampeninginteractionsstrength.



18

Spatialpatternsofphyto-andzooplanktondiversityinfloodplainsfromtheDanube

River(Austria):comparisonsbetweenfree-flowingandimpoundedstretchesInésO'Farrell1,GriseldaChaparro1,ThomasHein21Departamento de Ecología, Genética y Evolución, IEGEBA (UBA-CONICET), Facultad deCienciasExactasyNaturales,UniversidaddeBuenosAires,Argentina.2WasserClusterLunz–BiologischeStationGmbH,LunzamSee;UniversityofNaturalResourcesandLifeSciencesVienna(BOKU),AustriaNaturalriverinefloodplainsareamongthemostimportantdiversityhostsoftheworld,whichis mainly attributed to an elevated temporal and spatial heterogeneity associated to thedischargeregimeof theriver.Duetothedramaticratesof riverregulationworldwide,damsandartificial leveesblocked thedynamiceffectof thedischarge regime inavastmajorityoffloodplainareas.Wecomparedpatternsofphyto-andzooplanktonalphaandbetadiversitiesand environmental heterogeneity in floodplains along a free-flowing stretch (dynamicfloodplains)vsafloodplainlocatedinanimpoundedsection(stablefloodplain)oftheDanubeRiver (Austria).We included two nested spatial scales: 1- habitats (e.g. open waters,submerged, floating-leaved and emergent macrophytes) and 2- water sections within thefloodplainwetlands;wealsoconsideredtwocontrastinghydrologicalconditions(post-floodvsno-flood).Inbothhydrologicalconditions,environmentalheterogeneitywashigherindynamicwetlandsthaninthestablewetland;itwashigheramongwatersectionsthanamonghabitatsin dynamic floodplains but similar across scales in the stable one. Local diversity showeddifferent patterns among the studied groups andhydrological conditions. In general, overallphytoplanktonandrotiferβ-diversitieswerelowerinthestablethanindynamicfloodplainsinpost-flood conditions and similar among all wetlands in no-flood conditions. Formicrocrustaceans, overall β-diversity was similar among all wetlands in both hydrologicalconditions.β-diversitieswerehigherattheamongsectionsthanattheamonghabitatsscaleindynamicfloodplains;thesedifferencesweremorepronouncedforphytoplanktonandrotifersand in no-flood conditions. Our results show marked differences on diversity andenvironmental heterogeneity between dynamic and stable floodplains, potentially affectingecosystem functioning.Weare currently comparing thediversitypatternsusinga functionalapproachbasedonecologicaltraitsofthespeciesregisteredforafurtherunderstandingoftheecologicalstrategiespromotingspeciesreplacement.



19

PhytoplanktongrowthanddiversityintheCongoRiver:towardaparadigmshiftaboutphytoplanktondevelopmentinlargetropicalrivers?

DescyJean-Pierre1,2,MayaP.Stoyneva3,FrançoisDarchambeau1,AdrienLatli2,ThierryLambert1,StevenBouillon4,AlbertoV.Borges11Unitéd’OcéanographieChimique,UniversitédeLiège,Belgium2ResearchUnitinOrganismalBiology(URBE),UniversityofNamur,Belgium3DepartmentofBotany,UniversityofSofiaSt.Kl.Ohridski,Bulgaria4DepartmentofEarth&EnvironmentalSciences,KULeuven,BelgiumPhytoplankton sampleswere collected in theCongoRiver alonga1700km stretchbetweenKisanganiandKinshasaduringhighwater (HW,December2013)and fallingwater (FW, June2014). Phytoplankton was sampled in the main river, in tributaries and nearby lakes, andmeasurementsofprimaryproduction(using13Conboardincubations)andofvariousrelevantenvironmentalvariableswerecarriedout.BiomassandcompositionweredeterminedbyHPLCanalysis of chlorophyll a and marker pigments and by microscopy. Chlorophyll-aconcentrations differed between the two periods studied: in the mainstem they variedbetween 0.07 and 1.77 µg L-1 in HW conditions and between 1.13 and 7.68 µg L-1 in FWconditions. In terms of biomass, green algae dominated in the mainstem in HW, whereasdiatomsdominatedinFW;cryptophytesandcyanoprokaryotesweremoreabundantintheFWperiod,bothinthetributariesandinthemainchannel.NetprimaryproductionestimatedfortheCongoRiversites(n=30)variedbetween-442.6and148.4mgCm-2d-1inFWconditionsandbetween-64.7and204.0mgCm-2d-1 inHW.Communitygrowthrateswerecomprisedbetween -0.13 and 0.43 d-1 in FW and -0.07 and 0.63 d-1 in HW. We also explored howphytoplankton diversity changed along the river course, particularly in FW conditions.Taxonomicrichnesswashigh(>400taxa),withamajorcontributionofdiatoms,greenalgaeand cyanoprokaryotes, and was well correlated to chlorophyll-a. The main drivers of thecompositionat class/group levelwerenutrientconcentration (withaprominent roleofSRP)and light availability, depending on TSM affecting Secchi depth, but also on CDOM intributaries.Thisstudyprovidesevidencethatdevelopmentofphytoplanktonin largetropicalrivers may occur in the river itself, contrasting with the widely accepted view thatphytoplanktonmaintenance in theriverdependsongrowth in floodplain lakesconnectedtothemainstem.



20

Effectsofweatherandresourcelimitationontheoutcomeofcompetitionbetweendiatomsandcyanobacteriainman-madereservoirs

Petr Znachor1, Jiří Nedoma1, Pavel Rychtecký1, Josef Hejzlar1, RodanGeriš2 & DušanKosour2

1InstituteofHydrobiology,BiologyCentreofCzechAcademyofSciences,CzechRepublic.2MoravaRiverBoard,Stateenterprise,Brno,CzechRepublicWeather exerts strong impacts on phytoplankton both directly through physiology andindirectlybychangingwatercolumnstratificationandresourceavailability,whichinturnaffectphytoplankton seasonal dynamics.Diatoms and cyanobacteria are important components ofsummerphytoplankton;resourcecompetition,however,oftenleadstoexclusivedominanceofeithergroup.Bothgroupsdiffermarkedlyintheirphysiologicaladaptationstotheplanktoniclifestyle,resultingincontrastinglifestrategies.Cyanobacteriahaveavarietyofecologicaltraitsthatallowthemtoflourishinanutrient-rich,undisturbedepilimnion.Incontrast,diatomswithheavysiliceousfrustulesrelymainlyonturbulencetoremainentrained inthewatercolumn.Togetdetailed insights intomechanismsunderlyingcompetitionbetweencyanobacteriaanddiatoms, we analyzed a long-term data set of various environmental parameters from thesmallmesotrophicŘímovReservoiralongwithrecentdatafromintenseverticalprofilingofthewater column. In addition, we applied advanced fluorescence techniques depictingphysiological responses of diatoms to environmental forcing. Analysis of the time seriesconfirmedthatdiatomstendtodominateinrainyseasons,whilecyanobacteriaprevail indryand warm seasons, benefiting from the enhanced water column stratification. We alsoidentified a decisive role of nutrient pulses in the form of extreme rainfalls that representecological disturbances disrupting thermal stratification and shifting seasonal successiontowardsdiatomdominance. In theabsenceof suchextremeevents,diatomsquicklydepletedissolvednutrients(Si,NandP) intheepilimnionandaccumulateatthethermocline,wheretheir growth becomes light-limited. In periods of warm and sunny weather, diatoms aretrapped in the dark and are replaced by buoyant cyanobacteria that take over in theepilimnionuntiltheautumnmixing.Ourstudyimprovesourunderstandingofthemechanisticlinks between weather and phytoplankton dynamics and provides valuable hints that allowclimatechangeimpactsonaquaticsystemstobepredicted.



21

Crucial role of NO3-N concentration in shift between non-nitrogen-fixing andnitrogen-fixingcyanobacteriacommunityinXiaojiangRiverGaofeiSong1,ChunxiangXia1,YonghongBi11State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology,ChineseAcademyofSciences,ChinaCyanobacterial bloomsweremainly resulted from climate changeor humanactivity such asthe input of phosphorus and nitrogen. Although phosphorus is generally considered as theprime limiting nutrient responsible for cyanobacterial blooms, nitrogen may influence theshifts of cyanobacterial communities. In this study, we investigated the cyanobacterialcommunities at 7 sites along Xiaojiang River in China from January to December 2015, andaimedtoquantifytheeffectsofnitrogenconcentrationandotherenvironmentalvariablesoncyanobacteriadynamics.Therelationshipbetweenenvironmentalvariablesandcyanobacteriacommunities was analyzed by canonical correlation analysis, and the temporal patterns ofnon-nitrogen-fixing cyanobacteriawereanalyzedbynonmetricmultidimensional scaling.Theresults showed that the biomass percentage of non-nitrogen-fixing cyanobacteria increasedwith concentrationofNO3-N,while thebiomasspercentageof nitrogen-fixing cyanobacteriataxa decreased. Various environmental factors such as NO3-N concentration, watertemperature,turbidity,oxidationreductionpotentialwerefoundtoaffectthecyanobacterialcommunities intheriver,especially theNO3-Nconcentration,which is thekey factor leadingthe vigorous growth ofMicrocystis sp. and maintenance of serious bloom. Therefore, theconcentrationofNO3-Nshouldbecontrolledbelowthethresholdof1mg/Linordertolowerthe risk of non-nitrogen-fixing cyanobacteria (mainlyMicrocystis sp.) dominance of blooms.Thiswouldsupplyausefulstrategyforfreshwatermanagementswhenfacingcriticalblooms.



22

PlanktoMetrix:animageanalysissystemtosupportmicroscopeplanktoncountsandsizemeasurements

TamarZoharyKinneretLimnologicalLaboratory,IsraelOceanographic&LimnologicalResearch,Israel.PlanktoMetrix is a self-made computerized system, developed to conduct all steps ofconventionalmicroscope-basedphytoplanktonandzooplanktonanalyses(counting,measuringsizes,enteringdata,computations,storageindatabase)simultaneouslyusingreal-timedigitalimaging. Themicroscope field that displays the sample is continuously scanned by a digitalcamera and screened on a computer monitor, on which cell counts and measurements oflinear dimensions are made by mouse clicks. When the microscope tasks are completed,computationsofspeciesabundances,estimatesofbiovolumeper individual,speciesbiomassper unit volume, and total assemblage biomass concentration are made automatically andstored into a database. All raw and computed data are exportable to common spreadsheetplatforms. PlanktoMetrix offers the production of high-quality data in a standardizedprocedure,inlesstime,withloweruserfatigueandfewertypingerrors,makingitpossibletodevotemoretimetodataanalysisratherthangeneration.Furthermore,PlanktoMetrixallowscollectingorganism size data regularly, thus offering plankton ecologists a tool for followingseasonal,ontogenetic,andotherwell-documentedbutgenerallyignoredchangesinplanktonsize andmorphology. By applying this software, I discovered thatmany different species ofKinneretphytoplankton shared a similar annual patternof cell size fluctuations:within eachspecies,cellswerelargerinwinterandsmallerinsummer.Thoseseasonalfluctuationsincellsize occurred independent of the temporal dynamics of cell abundance and biomassconcentration.Thephenomenonwascommontospeciesfromthecyanobacteria,chlorophytaanddinoflagellates.ThedataforthisexcitingfindingcouldnothavebeengeneratedwithoutPlanktoMetrix. Iwillprovideanoverviewofthebasicstructureandfunctionofthesoftware,going intodetailswith those interested.PlanktoMetrix isdistributed free to interestedusersandwilllikelybeavailableinthefutureasanopen-sourceplatform.



23

Thefacilitationofcyanobacteriabloomsbyzooplanktonviapositivespeciesinteractions

KemalAliGer1,EwaldoLeitao1,RenataPanosso1,MiquelLürling21CenterforBiosciences,FederalUniversityofRioGrandedoNorte,Brazil.2Aquatic Ecology and Water Quality Management, Wageningen University Research, TheNetherlandsAlthoughbiotic interactions havebeen recognized as a key factor shaping communities, theroleofpositive interactions is lessunderstooddespiteamultitudeofexamplesshowinghowtheyregulatethestructureandfunctionofecosystems.Forexample,whiletop-downcontrolofphytoplanktonbyzooplankton isa cornerstoneofaquaticecology, cyanobacterialbloomsoften support high zooplankton biomass, raising questions whether zooplankton mightfacilitateratherthancontrolcyanobacteria.Wetestedhowkeyzooplanktonfunctionaltraits(i.e., grazing behavior and physiology) control the competition between cyanobacteria andeukaryotic phytoplankton, which were co-cultured in laboratory food chains over 4-6 days.Grazer traits were represented by various copepods and cladocerans from tropical andtemperate climates. The relative growth and abundance of co-cultured phytoplankton(Microcystis or Cylindrospermopsis with Cryptomonas) was compared in the presence orabsenceof eachgrazer. Experiments startedwitha6-fold initial dominanceofCryptomonasovercyanobacteriabybiomass.Wefoundthatgeneralistgrazers (i.e.,cladocerans)had littleeffect on the competition between cyanobacteria and eukaryotic phytoplankton, whileselective grazing copepods facilitated the dominance of the former. Not only did copepodsincrease the abundance of cyanobacteria relative to Daphnia, they also reduced theabundance of Cryptomonas, which reversed the initial dominance of Cryptomonas to favorcyanobacteria. Our results suggest that selective grazing zooplankton can facilitate bloom-formingcyanobacteriabygrazingontheireukaryoticcompetitors,whichmayexplaintheco-existence of these groups in nature. These results have implications for the role of positiveinteractionsinshapingphytoplanktondynamics.



24

PhytoplanktonandzooplanktonstructureinlakesofthePatagoniansteppe:theinfluenceofthefishintroduction

Irina Izaguirre1, Sol Porcel1, Juan F. Saad2, Inés O´Farrell1,María CristinaMarinone3,JulioLancelotti4

1Departamento de Ecología, Genética y Evolución, IEGEBA (UBA-CONICET), Facultad deCienciasExactasyNaturales,UniversidaddeBuenosAires,Argentina.2Escuela Superior de Ciencias Marinas, Universidad Nacional del Comahue, CONICET,Argentina.3Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas yNaturales,UniversidaddeBuenosAires,Argentina4Instituto Patagónico para el Estudio de Ecosistemas Continentales CENPAT, CONICET,Argentina.Most lakes of the basaltic plateaus of Patagonia are naturally fishless, but during the lastdecademanyof those locatedat the Strobel Plateauhavebeen stockedwith rainbow trout(Oncorhynchus mykiss). Fish introductions have been identified among the main causes ofalterations in lakes, and studying the effects caused by exotic fish in lakes of this region isrelevantbecausetheyconstitutethemainfeedingandbreedinghabitatforseveralwaterbirdspecies,includingendemicthreatenedspeciessuchasthehoodedgrebe(Podicepsgallardoi).WesurveyeddifferentfishlessandfishstockedlakesoftheStrobelPlateauinsuccessivefieldtrips, andwe analyzed the structure of phytoplankton and zooplankton.Our study revealedthat phytoplanktonwas affectedby thepresenceof fish, probably due to a trophic cascadeeffect, registering the lowest phytoplankton biomass in fishless lakes. Phytoplanktonassemblages also differed between both lake types: fishless lakes exhibited a higherproportionofnanoplanktonictaxa,manyofthemmixotrophic,belongingtofunctionalgroupsX1,X2,Y,DandMP;fishstockedlakesshowedahigherproportionofspecies>20µm,higherabundanceofcyanobacteriainsomeofthem,andthemainfunctionalgroupswereK,F,Lm,P,MPtogetherwithX1andX2.Wealsofounddifferencesinthezooplanktonstructurebetweenfishlessandfishstockedlakes,withahigherabundanceofmacrozooplanktonandCrustaceainfishlessones.Ontheotherhand,wefoundthattheeffectoffishintroductionsonplanktoniccommunities seems to be potentiated by a decrease in the water level of the lakes that istakenplaceintheregionasaconsequenceoflowerprecipitation.



25

Phyto-andzooplanktoninteractionsandresponsetophysico-chemicalconditionsintwomorphologicallydifferenteutrophiclakeswithphosphorusrichanthropogenic

sedimentsKirstenOlrikLaboratoryofEnvironmentalBiologyApS,HenningsensAllé2C,DK-2900Hellerup,DenmarkPhyto- and zooplankton seasonal variations were studied through 20 years in shallowpolymictic Lake Arreskov and dimictic Lake Søholm (max depth 16 m).In Lake Arreskov,suspension-feeding Daphnia dominated year round. In winter and spring, phytoplanktonconsisted of small diatoms, succeeded by small chlorophytes. Due to heavy grazing, andsimultaneousnitrogenlimitationandphosphorusreleasefromthesedimentduringsummer,ahugebiomassofgrazing resistant. LargeN2-fixing cyanobacteriadeveloped (Aphanizomenonand Dolichospermum). Nevertheless, the persistence of Daphnia through summer indicatesthat apart from large cyanobacteria, small phytoplankton species must have been present,althoughtheydidnotoccurinthesamplesduetograzing.Lake Søholm is situated in the same glacial landscape and has had similar historicalanthropogene phosphorus enrichments as Lake Arreskov. Due to stratification anddevelopmentofbothathermoclineandanoxyclineduringsummer,phyto-andzooplanktoninthis lake are entirely different from that in Lake Arreskov. The spring diatom maximumconsisted of larger species that circulate in the entirewater columnwhereDaphnia cannotfollowthem.Assoonasthethermoclineisestablished,inorganicphosphorusandnitrogenintheepilimnionisrapidlydepleted.Duringsummer,anoxiaadvancesthroughthehypolimnionand presses the oxic epilimnion. Neither autotrophic phytoplankton nor zooplankton werepresent, except for a few cyclopoid carnivore copepods. Instead, a huge biomass of themixotrophic dinoflagellateCeratium developed. As half oxygen producing plant, half animal,Ceratium can utilize the released phosphorus and bacteria in the microaerophilic oxycline,where no autotrophic phytoplankton and true heterotrophic zooplankton can exist, andreplacesboth.



26

Variabilityofintraspecificbodysizevariationtofunctionalgroups,phytoplanktoncommunitiesandsizedistributionalongpredatorgradientsintropicallakes

Letícia Barbosa Quesado1, Caroline Souffreau2, Luc De Meester2, Camila RodriguesCabral1,FabíoladaCostaCatombéDantas1,AndréMegaliAmado3,AdrianoCaliman1&LucianaSilvaCarneiro11LaboratóriodeEcologiaAquática,UniversidadeFederaldoRioGrandedoNorte,Brazil.2LaboratoryofAquaticEcology,EvolutionandConservation,Belgium.3LaboratóriodeLimnologia,UniversidadeFederaldoRioGrandedoNorte,Brazil.Trait-based approaches are increasingly used in community ecology to explain and predictfunctional community structure and dynamics in response to environmental gradients.Intra-specific trait variation (ITV) havebeen shown that canbe the responsible for the totalvariationinthecommunity.Inthisstudy,weinvestigatedthefunctionalresponseinbodysizeof phytoplankton communities along predator gradient among-community and the relativeimportanceofITVforthespeciesvariationandtheirfunctionalgroupswithin-community.Forthis,westudiedbodysizeresponsesacrossmedium-size(Cyclopoida,CalanoidaandCladocerabiomass) and small-size (Rotifera biomass) predator gradients within 98 phytoplanktoncommunitiesand8morpho-functional groups (MBFG) innortheastBrazil.Our findings showthat only diatoms respond to medium-size predator, reducing their variability with highpredator biomass. On the other hand, species respond differently from within functionalgroups and total within-community body size variation. Where groups with high relativeabundance, asGIII,GV, andGVI didn’t present pattern, edible algae (GI andGIV) presentedlower variability compare to their functional groups and large protected algae (GVII) variedmore within-species. When compared to the ITV within-community, species from differentfunctionalgroupswereresponsibletothechanges.Filamentous,mucilaginous,andpotentialtoxicalgae(GIII,GVIIandGVIII)variedmorethantotalcommunity.Overall,ITVpresentedlowcontribution to the total variation, nevertheless showed different importance to distinctgroupsandonlysensibletomediumpredatorinfluence.



27

Resistingannihilation:Relationshipsbetweenfunctionaltraitdissimilarity,self-

organizedbiodiversityandallelopathyRikaM.W.Muhl1,DanielL.Roelke1,JoydebBhattacharya1,FrancesG.Withrow11 DepartmentofWildlifeandFisheriesSciences,TexasA&MUniversity,USA.Allelopathicphytoplanktonspeciescanalterphytoplanktonbiodiversityandsuccession,intheextreme producing near-monospecific blooms. It is likely, however, that exploitativecompetition lessensthe impactof interferencecompetition, in thiscaseallelopathy. Itmightbe that assemblages aremore resistant to bloomswhen non-allelopathicmembers stronglycompete exploitatively against allelopathic species. We test this notion theoretically usingecological modeling, with follow-on analyses using empirical data spanning multiple yearsacross different system types. Previous multi-nutrient, multispecies plankton models haveshown thathighbiodiversity canbe sustained in theabsenceofexternaldisturbanceswhenthecompetitiveabilitiesofcoexistingspeciesareneutral,lumpyorintransitive.Dissimilarityinspecies traits relating to competition is least in neutral assemblages (by definition) andgreatestinintransitiveassemblages.Tothesemodels,weaddedallelopathybymakingoneofthecoexistingspeciesanallelochemicalproducer.Throughsensitivityanalysis,wediscoveredthat neutral assemblages were the most vulnerable to blooms of the allelopathic species,followedbylumpyandintransitiveassemblages,whichweremorerobustagainstallelopathy.Usingempiricaldata,wearecurrentlytestingsomeofourtheoreticalfindings,specificallythefindingthatlumpyassemblagesaremoreresistanttobloomsofallelopathicspeciesthanareneutralassemblages.Assumingcell-sizeclassasaproxyfordifferencesincompetitiveability,we are exploring time-series phytoplanktondatasets fromaround theworld todiscern linksbetweenbloomincidenceandphytoplanktonsizeclassstructure.Earlyobservationsshowthatsystems plagued by blooms do not have as broad of a range in phytoplankton size classes.These observations, if consistent, suggest a fundamental principle of harmful algal bloomecology.



28

Limitingsimilarityandenvironmentalfiltering:potentialassemblyrulesforeutrophic

lakephytoplanktonGáborBorics1,ViktóriaB-Béres1,IstvánBácsi2,BalázsA.Lukács1,GáborVárbíró11MTA Centre for Ecological Research, Danube Research Institute, Department of TiszaResearch,Hungary.2DepartmentofHydrobiology,UniversityofDebrecen,HungaryDespitetheevidentdifferencesbetweenterrestrialandplanktonicsystemstherearegeneraltheories in ecology which can be successfully applied to explain diversity and speciescoexistence in these contrasting ecosystems. Recent evidences suggest that trait basedapproaches provide more information on community assembly rules than those based onspecies identities. Therefore, applicability of the concept of `limiting similarity andenvironmental filtering` was studied for lake-phytoplankton focusing on divergence andconvergenceof traitsalongvariousgradients.Our result revealed that limitingsimilarityandenvironmentalfilteringmayoperatesimultaneouslyinthephytoplanktonbutactondifferenttraitsandhavedifferentimportancealongthescales(temporalortrophicscale)studied.Theseresultsareinaccordancewiththosefoundformacroscopicterrestrialsystems,whichimpliesthat in terms of the functioning of the ecosystems an intriguing parallelism can be drawnbetweenterrestrialsystemsandphytoplankton.



29

18th IAP ABSTRACTS POSTER PRESENTATION

(alphabeticorder,byfirstauthor’sname)

IncreaseofcyanobacteriaintheRiverLoire:mythorreality?András Abonyi1; Jean-Pierre Descy2; Anne Marie Lançon1; Maria Leitao1; CamilleMinaudo31Bi-Eau,France.2ResearchUnitinEnvironmentalandEvolutionaryBiology,UniversitédeNamur,Belgium.3DepartmentofGeosciences,UniversityofTours,France.Therehasbeenwidespreadconcernthatclimatechange,combinedwitheutrophication,willresult in increasing theoccurrenceofpotentially toxicblooms in freshwaters,particularly inlakes where extended periods of stratification and longer residence time are expected toincreasetheoccurrenceofcyanobacteriablooms.Sofartherehavebeenfewstudiesreportingincreasesofcyanobacterialabundanceinriversthatcouldberelatedtoclimatechange.Inthisstudy, based on phytoplankton monitoring data, we examine long-term trends inphytoplankton development in the Loire River, France, with a focus on the contribution ofcyanobacteria to total phytoplankton biomass.We expected that (1) cyanobacteria biomasswould be higher in low-flow years than in high-flow years (2) cyanobacteria biomasswouldexhibit a downstream increase, as a result of retention time increase (3) that cyanobacteriaoriginating from upstream eutrophic reservoirs would decrease in the river and (4) thatdiminished P availability due to improved wastewater treatment would in the long termreducethelikelihoodofsignificantdevelopmentofbloom-formingcyanobacteria.Theresultsshowthatphytoplanktonbiomasshasdramaticallydecreased in theRiverLoireand itsmaintributaries, suggesting a relation with the implementation of measures to controleutrophication.Incontrastwithotherstudiesthatreportedchangesinbenthicandplanktoniccommunities,wedidnotdetectanysignificantincreaseofthecontributionofcyanobacteriatototal phytoplankton: cyanobacteria were most of the time a very small fraction of totalphytoplanktonbiomass (onaverage1.05%),excepton rareoccasions.Asexpected,mostofthe planktonic taxa (Aphanizomenon, Limnothrix, Microcystis, Planktothrix) reached theirmaximalabundance in the lowerLoire,and the large interannualvariationcanbe related tothevariationinhydrologicalconditions.Moreover,thesubstantialreductionofPinputstotherivernetworkhasinducedsignificantP-limitationofphytoplanktongrowth,furtherdiminishingthe likelihood of cyanobacteria blooms in the R. Loire, suggesting that hydrological changesexpected from climate change will not result in increasing the risk of potentially toxicphytoplanktonblooms."



30

Thealternativestatesinbraziliansemiaridlakes:InteractionsbetweenCharophyteandphytoplankton

LucianaGomesBarbosa1,RafaelMachadodeAraújoAlves11LimnologyLaboratory,UniversityofParaiba,Brazil.The dynamics of the shallow lakes in the Brazilian semiarid is directly influenced by theirregularity of the rainfall regime, human activities among others. In these habitats, thevulnerabilities to eutrophication are associated with water level fluctuation and sedimentresuspension. The recognized role of the high density of submerged macrophytes in therestoration of shallow lakes indicates the contribution of these species in the removal ofphosphorus, reduction of turbidity, promoting the environmental stability and preventingbloomsof thecyanobacteria. Inthisstudy,wetestedthedirectand indirecteffectsofbioticand abiotic variables through the Partial Least Squares PathModeling in two shallow lakes:Santa Lucia with clear water and the presence of submersed macrophyte (includingCharophytes) and Pao Lakewith turbidwaters and the blooms of cyanobacteria (functionalgroups: SN,M, H1). For each lake amodel was created with the quantitative effects of therelations between the variables. Themodel in Saint Lucia had as themost direct influencevariables the percentage volume infestation (PVI), biomass of the phytoplankton, totalphosphorus in the water followed by the phosphorus in the sediment. The relationship ofphosphorus with PVI and phytoplankton biomass in Santa Lucia lake reflects the valuesphosphorusfoundintheenvironment,withhighersedimentconcentrations.InPaó,probablydue to the absence of themacrophytes,we highlight the direct effect of phosphates in thewaterinphytoplanktonbiomass,resultedinanincreaseinthepotentiallytoxiccyanobacteria.In conclusion, the cover of submerged macrophytes it was a stabilizing force, reducingphosphorusreleasefromlakesedimentandpresenceofcyanobacteria.



31

Droughtfavorsthedominanceofediblephytoplanktoninsemi-aridman-madelakesVanessaBecker1,RosembergF.Menezes2,MarianaR.A.Costa11Laboratório de Recursos Hídricos e Saneamento Ambiental, Departamento de EngenhariaCivil,UniversidadeFederaldoRioGrandedoNorte,Brazil.2DepartamentodeFitotecniaeCiênciasAmbientais,UniversidadeFederaldaParaiba,Brazil.Phytoplankton organisms show a wide range of shape diversity (e.g. round cells, filaments,coenobial,andothercomplexshapes).Bodysizeisrecognizedtobeanimportanttraitrelatedto physiological and ecological performance of planktonic organisms. Phytoplankton hasevolved variousmorphological types andbehaviordefensemechanismsagainst zooplanktongrazing.Ourmaingoalwastotestifthedominanceoffilamentousandcolonialphytoplanktontypes driven by drought intensification hinders/prevents zooplankton grazing even amongspecialistpredators.Ourstudywasperformedintwosetsofreservoirs(n=16)locatedintwosemi-arid sub-basins. For phytoplankton, it was considered the body size and morphologyshape, whereas for zooplankton the food size and feeding habits were used. Our resultsshowedthatdroughtintensificationreduceswaterlevel,increasingthenutrientsandturbidity,decreasing light availability. Hence, these factors induce a shift in phytoplankton functionaltraits.Duringthedroughtperiod,thespecialistpredators(copepods)andgeneralistmedium-filters(cladocerans)displayedasignificantinverselog-logrelationshipwithlargeround/ovoidcells,respectively(r2=0.40,p=0.0001;r2=0.17,p=0.018).Also,ahighlysignificantandnegativerelationshipbetweengeneralistmedium-filters(cladocerans)andcomplexformswasobserved(r2=0.14, p=0.04). There was a highly significant and positive log-log relationship betweensmall-predatorsandsmall round/ovoidcells (r2=0.23,p=0.006).Neither zooplanktonsizenorfeeding habits was related to filamentous and colonial shapes. The drought intensificationfavoredtheediblephytoplanktonspecies,assingle largeround/ovoidcells,andrelationshipswithspecialistpredatorsandgeneralistmedium-filters.



32

Temporaldynamicsofplanktoncommunitiesintemperateshallowlakeswithdifferentphosphorusconcentrations

MaiteColina1,CarolinaCrisci2,GissellLacerot1,CarlaKruk1,31Ecología Funcional de Sistemas Acuáticos. Centro Universitario de la Regional Este.UniversidaddelaRepública,Uruguay.2Modelización y Análisis de Recursos Naturales. Centro Universitario de la Regional Este.UniversidaddelaRepública,Uruguay.3SecciónLimnología,InstitutodeEcologíayCienciasAmbientales(IECA).FacultaddeCiencias.UniversidaddelaRepública,Uruguay.Phytoplanktonandzooplanktontrophicinteractionsarecrucialinmatterandenergyfluxesinfreshwaters. Both communities fluctuate temporally in biomass and composition and theirdynamicscanbeeithersynchronous(abiomassincreaseinonecommunitycausesabiomassincreaseintheother)orcompensatory(thesameincreaseleadingtobiomassdecrease).Ithasbeenpredictedthatincrementsinnutrientsconcentrationfavorssynchronousdynamicsovercompensatory ones, strengthening bottom-up control. However, few studies have analyzedhow nutrient concentration affects those dynamics. The aim of our work was to studytemporal dynamics of phytoplankton and zooplankton communities of temperate shallowlakeswithcontrastingphosphorusconcentrations.Weanalyzedthree-yeartemporalseriesofseven shallow lakes from the Wall river floodplain in The Netherlands, with averagephosphorusconcentrationsbetween60and650µgL-1.Phytoplanktonbiomassincreasedwithphosphorous,whilezooplanktonabundancewashigherat intermediateconcentrations inalllakes. Spectral analyses showed that periodic fluctuations of phytoplankton biomass wererelatedtosmaller frequencies (higherperiods)atsmallerphosphorousconcentrations,whilethe reverse situation was observed for periodic fluctuations in zooplankton abundances.Regarding the cross-correlation spectral density results between phytoplankton andzooplankton, we observed that their series were correlated presenting a peak of commonoscillation.Thispeakoccurredearlierforthezooplanktonseries,allowingevaluatingtheeffectof zooplanktongrazinguponphytoplankton. Inall cases thedegreeof correlationdecreasedwith higher phosphorous concentrations, indicating weaker compensatory dynamics.However, no significant synchronous dynamics were found. Our results indicate that highphosphorousconcentrationsinlakesareassociatedwithlowerconsumptionofphytoplanktonprimary production by herbivore zooplankton, due to an uncoupling in compensatorydynamics.This timeseriesanalysis shed lightoneutrophicationconsequencesoverplanktondynamics,anditssynergisticeffectswithclimatechange.



33

PhytoplanktonspeciesinteractionsduringtheinvasionprocessofCeratiumfurcoidesinaeutrophictropicalshallowreservoir.

Luciane Oliveira Crossetti1, Denise de Campos Bicudo2, Carla Ferragut2, SamanthaBorgesFaustino2,CarlosEduardodeMattosBicudo21DepartamentodeEcologia,UniversidadeFederaldoRioGrandedoSul,Brazil.2NúcleodeEcologia,InstitutodeBotânica,SMA,Brazil.WiththerecentarrivaloftheinvasivespeciesofCeratiuminfreshwateraquaticecosystemsofSouth America, changes in structuring patterns of the phytoplankton community have beenrecorded. In this sense, one may question whether the interactions classically recordedbetween this and other phytoplankton species, especially cyanobacteria, will be similarlyobservedinecosystemswherethisspeciesisinvasive.Theobjectiveofthepresentstudywastoexplorethe interactionsofphytoplanktonspeciesduringthe invasionprocessofCeratiumfurcoidesinatropicalshalloweutrophicreservoir(GarçasLake,southeasternBrazil),whichhasbeen monitored for twenty years (1997 – 2017), in a monthly basis. Because of that, C.furcoides establishment could be registered in spring of 2014, coincidingwith the historicaldrought in the region, which reduced significantly the rainfall and decreased the externalnutrient loading, especially phosphorus. This scenario appeared to have configured thenecessary disturbance for defeating the Cyanobacteria long term steady-state found in thereservoir (Microcystis aeruginosa, M. panniformis and Cylindrospermopsis raciborskii),increasingthewatertransparency,recruitingC.furcoidespopulations.Sincethen,C.furcoidespopulations are being recorded in the water column mixing periods, coexisting withCryptomonasspp.andTrachelomonasspp.,alternatedbythepopulationsofMicrocystisspp.(always presenting low biomass values), diatoms species (Synedra acus,Nitzschia sp.) and,eventually, some desmids (Staurastrum sp.). Higher biomass of this dinoflagellate has alsobeen associated to the higher concentrations of dissolved nitrogen forms and intermediateZmix:Zeuratios.ThehighercompetitiveadvantagesofC.furcoidesseemtoplayanimportantrole in recruiting space and nutrients in Garças Lake, so that negative interactions withcyanobacterialspecieshavebeenidentified.

Financingsupport:FAPESP,CNPq



34

Seasonalchangesinstructureandtrophicinteractionsintheplanktonicfoodwebin

aeutrophictropicalreservoirCarolina Davila Domingues1, Kamylla Andreoni1, Luciana Machado Rangel1, BetinaKozlowsky-Suzuki2, Marcelo Manzi Marinho3, Rodolfo Paranhos4, Anderson Cabral4,HugoSarmento5,SandraMariaFelicianodeOliveiraeAzevedo6,LúciaHelenaSampaiodaSilva11Laboratório de Ficologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio deJaneiro,Brazil.2NúcleodeEstudosLimnológicos,UniversidadeFederaldoEstadodoRiodeJaneiro,Brazil.3Laboratório de Ecologia e Fisiologia do Fitoplâncton, Universidade do Estado do Rio deJaneiro,Brazil.4LaboratóriodeHidrologia,UniversidadeFederaldoRiodeJaneiro,RiodeJaneiro,Brazil5LaboratóriodeBiodiversidadeeProcessosMicrobianos,UniversidadeFederaldeSãoCarlos,SãoPaulo,Brazil.6LaboratóriodeEcofisiologiaeToxicologiadeCianobactérias,UniversidadeFederaldoRiodeJaneiro,Brazil.Funil reservoir (Brazil) has been studied for the last two decades as a model of eutrophicsystemwithintensetoxiccyanobacteriabloomsandhighcontributionofcopepods.However,it has been observed a reduction of orthophosphate (SRP) concentrations in recent years.Moreover, the invasive dinoflagellate Ceratium furcoides was firstly recorded in the end of2013inthissystem.Thisstudyaimstodisentanglespatialandtemporalresponsesofplanktondynamic (picoplankton, phytoplankton, protozooplankton, andmetazooplankton) in relationto those changes. Due to the eutrophic conditions and copepod dominance, we expect ahigher contribution of classical food web carbon biomass (from phytoplankton tometazooplankton),whileanimportantcontributionofheterotrophicnanoflagellates(HNF)forprotozooplankton.Monthly integratedsamples intheeuphoticzoneweretakenduring2015atthetransitionzoneandneartothedam.Physicalandchemicalvariablesweremeasuredbyprobes and analytic methods, and the carbon stock of each planktonic component wasestimated.Weobserved lowSRPconcentrationswithpotential limitation forphytoplankton,andnospatial variationonabioticandplanktoniccommunity.Redundancyanalysis revealedthathighertemperature,dissolvedoxygenandtotalnitrogenconcentrations,conductivity,andpH were related to the hot-rainy (HR) in comparison to the cold-dry (CD) period.Cyanobacteria,Mesocyclopsspp.andNotodiapatomusinheringiwerepositivelyrelatedtoHRperiod, while C. furcoides was mainly related to lower temperatures at CD period.Cryptomonads, Daphnia spp.,microzooplankton and picoplanktonwhere also related to CDperiod.Carboncontributionoftheclassicalfoodwebwashigherthanthemicrobialfoodweb,except at the transition zone on the CD period. Nevertheless, HNF were important toprotozooplanktoncarbonstockthroughouttheyear.Temperatureappearedtobeakeyfactoraffecting seasonal plankton structure and trophic interactions in this tropical reservoirsubjectedtotheinvasivedinoflagellateC.furcoides.



35

Spatial-scalesandlocalfactorsinfluencingnanoflagellatesassemblagefromafloodplainfluvialsystem

VanesaDiPasquale1, FernandoUnrein2,MaríaPaulaHuber1, SebastiánMetz2,GiselaMayora1,BereniceSchneider1,MelinaDevercelli1.1InstitutoNacionaldeLimnologia,CONICET,UniversidadNacionaldelLitoral,Argentina.2InstitutodeInvestigacionesBiotecnológicas-InstitutoTecnológicodeChascomús(IIB-INTECH),UniversidaddeSanMartín,Argentina.Nanoflagellatesarefunctionallyimportantcomponentsoftheplanktonandinmicrobialfoodwebssincetheylinkthedifferentpathofenergyflowduetotheirheterotrophic,autotrophic,and mixotrophic nutrition. The variability in nanoflagellates assemblage among habitats isregulatedbya combinationofabiotic factors,biotic interactions,anddispersalprocesses. Infloodplain fluvial systems, the dispersal potential is mainly related to the hydrologicalconnectivityofhabitatsandhence, to thespatial configuration. In this sense, theshapingoflocalcommunitiesdependsnotonlyonthelocalenvironmentalfactors,butalsoonthespatialprocesses operating at multiple scales as it is stated in the metacommunity frame. Theobjective of this work was to analyze the different factors and scales intervening in thenanoflagellates’assemblyof theMiddleParanáfloodplain.Withthispurpose,wecompare i)two geomorphological units characterized by different drainage pattern and connectivitystrength(meanderingandanastomosed), ii)typeofenvironmentswithdifferenthydrologicalinfluence,andiii)patcheswithineachenvironment(pelagicandvegetated).Atotaloftwenty-eight lotic and lentic environments were sampled during a low water period.When it waspossible, pelagic, and vegetated sampling points were established. The morphologicalidentification and counting of nanoflagellates assemblage was performed using anepifluorescencemicroscope.Measurements of spatial, physical, and chemical variables, andmacrophyte coverage and composition were made. Additionally, heterotrophic, andphototrophic picoplankton were counted by flow cytometry since they are considered themain food source of heterotrophic flagellates. We decomposed the variation explained byspatial (dbMEM eigenfunction) and local factors by a variance partition analysis. Weperformed NPMANOVA and SIMPER to compare nanoflagellates structure amonggeomorphological units, environments, and patches, and the assemblage divergence wasanalysedwithPERMDISP.



36

PhylogeneticdiversityoffreshwaterpicocyanobacteriaPaulaHuber1&FernandoUnrein2

1InstitutoNacionaldeLimnología,ConsejoNacionaldeInvestigacionesCientíficasyTécnicasyUniversidadNacionaldelLitoral,CiudadUniversitaria,ParajeElPozo,Argentina.2Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús, ConsejoNacional de Investigaciones Científicas y Técnicas y Universidad Nacional de San Martín,Argentina.Thephylogeneticrelationshipsoffreshwaterpicocianobacteriaremainpoorlyknown.Studiescarried out in freshwater systems are still scarce and restricted to a limited number ofenvironments.Here,weaimedatexpandingtheknowledgeaboutthediversityoffreshwaterpicocyanobacteria linkingphylogeneticandmorphology informationwithecologicaltraits.Toinvestigate this, we constructed phylogenetic trees based on 16S rRNA and 16S rRNA+ITSsequences from literature and 206 new sequences from strains and environmental clonesretrievedfromeutrophicpampeanshallowlakes.Thetopologyofthetwophylogenetictreesweresimilar,andconsistentwithpublishedtrees.Weidentified17cladespreviouslydescribedby other authors and 8 new lineages, 5 ofwhichwere exclusive to pampean shallow lakes.Somecladeswere cosmopolitanwhileotherswere restricted to certainenvironment. In the16SrRNA+ITStreethemostcosmopolitancladesweredividedintosubclades,thatseemstoberelatedwithparticularlimnologicalfeaturesofthesystems.Atleast6cladeswereconformedbysingle-cells(Pcy)andcolonial(CPcy)picocyanobacteria,whileothercladeswereexclusiveofeach morphotype. Our findings revealed the existence of a great phylogenetic diversity offreshwater picocyanobacteria, and highlighting the importance of enlarge the data set withsequencesfromdifferentenvironments.Besides,ourresultssupporttheimportanceoftheITSregion in phylogenies of picocyanobacteria as a valuable molecular marker that allows theanalysisofmicrodiversitywithinlineagesofcloselyrelatedtaxa.Finally,wecanconcludethatthe colonial and unicellular morphotypes of picocianobacterias are closely related, and thephenotypic plasticity of Synechococcales (i.e. the ability of single-cell to aggregate intocolonies)wouldbeassociatedtocertainphylogeneticgroups.



37

DiversityofphotosyntheticpicoeukaryotesfromeutrophicshallowlakesSebastiánMetz1,AdrianaLopesdosSantos2,ManuelCastro1,EstelleBigeard2,HoracioZagarese1,FabriceNot2,EnriqueLara3,FernandoUnrein11InstitutodeInvestigacionesBiotecnológicas-InstitutoTecnológicodeChascomús(IIB-INTECH),UNSAM-CONICET,Argentina.2LaboratoireAdaptationetDiversitéenMilieuMarin,StationBiologiquedeRoscoff,SorbonneUniversités,UPMCUniversitéParis,France3LaboratoryofSoilBiology,UniversityofNeuchâtel,Switzerland.The diversity of photosynthetic picoeukaryotes (PPEs) from marine ecosystems has beenintensively studiedduring lastdecades,whereas the compositionof freshwaterPPE remainslargely ignored. Here, we combined flow cytometry, microscopy and high throughputsequencing(IlluminaMiseq)tostudythePPEdiversityinsixeutrophicandturbidshallowlakesacrossSouthAmerica.Moleculardiversitydatawereobtainedfromtotalplanktoncommunityon filter (FTP) samples (<20µm) as well as on PPEs concentrated by flow cytometry sortingbasedon chlorophyll fluorescence.A total of 316Operational TaxonomicUnits (OTUs)wereidentified from sorted PPEs, among them 43 had a contribution >1% in each sample. Asexpected,mostreadsfromthesortedpopulationbelongedtophotosyntheticorganisms(avg.82%ofthetotalsequences).TreubouxiophyceaedominatedPPEcommunitiesin4lakes(50-90%of thesequences),whileChlorophyceaeanddiatomsdominated inthetwoother lakes.Potential parasites (mostly Chytridiomycetes and Ichthyosporea) were relatively abundant(range 10 - 45% of the sequences) in the lake dominated by diatoms. DominantTreubouxiophyceaeOTUs belonged toChoricystis, Chlorella (sensu stricto) andNannochlorisclades; Chlorophyceae to generaMychonastes and Diatoms to the pico-sizedCyclotella andChaetoceros genera. Dominant groups among PPEs (e.g. Treubouxiophyceae) were poorlyrepresented in FTP samples. Richness of Treubouxiophyceae was on average 2 orders ofmagnitude higher in the sorted samples. Moreover, a significant number of OTUs wereexclusivelyfoundinthesorted,PPEenriched,samples,emphasizingthatsequencesfromFTPsampleunderestimatesthediversityofthesesmallorganisms.Besides,30%oftheOTUshadalowsimilarity(<95%)witheitherculturestrainsorenvironmentalclonesequencesinthethreeprincipal classes (Trebouxiophyceae, Chlorophyceae and Bacillariophyceae), demonstrating ahighpotentialfornewspeciesandgeneradiscoveryinthePampeanlakes.



38

PresenceofCeratiumfurcoidesinthewaterqualitymonitoringprograminthestate

ofSãoPauloanditsimplicationsDeniseAmazonasPires1,LucianaHaipekMosolinoLerche1,MariadoCarmoCarvalho1,MartaCondéLamparelli11CompanhiaAmbientaldoEstadodeSãoPaulo,Brazil.Water quality monitoring is one of the main tools for making decisions regarding waterresources preservation, as well as towards its multiple and rational use. Phytoplanktoncommunity has been widely used in monitoring, mainly in reservoirs. Because they live insuspensioninthewatercolumn,theyrespondquickly(indays)toenvironmentalchangesduetoanthropicornaturalinterferences,whichcausechangesinthecomposition,structure,andgrowthrateofthecommunity.InSãoPauloState,locatedintheSoutheastofBrazil,CeratiumfurcoideswasfirstrecordedbytheEnvironmentalStateAgency(CETESB)monitoringprogramin 2008, at Billings and Guarapiranga reservoirs. These reservoirs are in the metropolitanregionofSãoPauloCity. Inthismonitoringprogram,physicalandchemicalanalyzesarealsoperformed. Since then the genus Ceratium was registered in several rivers and reservoirsthroughout theState in:2009ChannelofFuga -Cubatão;2010 Itupararangareservoir;2011Jaguari reservoir (Piracicaba Basin), Barra Bonita reservoir and CorregoMarinheirinho; 2012AtibaiaandPiracicabarivers;2013Jaguarireservoir(ParaíbadoSulBasin)andÁguadoNortereservoir; 2014 Santa Branca reservoir and all reservoirs of the Cantareira System (Jaguari-Jacareí,Cachoeira,Atibainha,JuqueriandÁguasClaras)and in2015CapivariandPiraírivers,Jundiaí, Taiaçupeba and Promissão reservoirs. The results demonstrate that in the last nineyears the genus Ceratium has spread in the State in either lotic and lentic waterbodies, ineutrophicandoligotrophicwaters,causingshifts inthephytoplanktoncommunity,especiallywhendominant.Ineutrophicreservoirs,adecreasecyanobacteriadensitywasobserved,suchas at theBillings reservoir.On theotherhand,other implications in aquaticbiota canoccursuchasfishmortality,eitherbyvariationsofdissolvedoxygenorbycloggingofgills.



39

PhytoplanktonassemblagesinlakesofthearidPatagoniawithrelevanceforbiodiversityconservation

SolPorcel1;InésO'Farrell1,JuanF.Saad2&IrinaIzaguirre11Departamento de Ecología, Genética y Evolución, IEGEBA (CONICET-UBA), Facultad deCienciasExactasyNaturales,UniversidaddeBuenosAires,Argentina.2Escuela Superior de Ciencias Marinas, Universidad Nacional del Comahue, CONICET,Argentina.FifteenlakeslocatedinthebasalticBuenosAiresplateau(SouthernPatagonia)weresampledduring the warm seasons since 2015. Some of the water bodies are located in a recentNationalPark(Patagonia),whichwasprincipallycreatedtoprotectsomethreatenedwaterbirdspecies,suchasthehoodedgrebe(Podicepsgallardoi).Thelakesofthisplateaudifferintheirmorphometry, trophicstatusandtransparency; someof themare inorganic turbidwithhighamount of suspended material (Kd 6.25 - 28.11 m-1), but most are clear and profuselyvegetated (Kd 0.48 - 1.51m-1). Those lakes located at higher altitudes (> 1200m.a.s.l.) arevegetated and more suitable for waterbird nesting, being particularly important forbiodiversity conservation; in these lakes we found high phytoplankton diversity, includingsomeendemicdesmidspeciesnewforthescience.Totalphytoplanktondensitywasabout500ind.ml-1inthemostoligotrophiclakes,andachievedaround50,000ind.ml-1intwovegetatedlakes.ThebiggestlakeoftheNationalPark(ElSello),locatedatthehighestaltitudeamongthestudiedwaterbodies,isthemostimportantinrelationtowaterbirdconservation;inthislakephytoplanktonneverexceeded28,000ind.ml-1andthedominantfunctionalgroupswereY,X2and X1. The highest phytoplankton densities were registered in Chapu and Cevecero lakes,where the most important coda were X2, X1, F and J. The last years a drastic water leveldecreasewasobservedinmostlakesoftheregionduetoadeclineinprecipitation,whichleadto the complete dry of some water bodies; this was accompanied by a change inphytoplanktonassemblages,withanincreaseofcyanobacteria(S1,Sn),anddiatomsbelongingto MP. Our studies are showing that the reduction in the hydrometric level generatesstructural changes in the lakes,with declining ofmacrophytes andmodifying their planktoncommunities.



40

Ceratiumfurcoides(Dinophyceae)invasioninaeutrophictropicalreservoirwitha

historyofpersistentcyanobacterialblooms"Luciana M. Rangel1, Carolina D. Domingues1, Iamê A. Guedes2, Rafael R. Paiva3,MarceloM.Marinho4,SandraM.O.F.Azevedo2,LúciaHelenaS.Silva11LaboratóriodeFicologia,DepartamentodeBotânica-MuseuNacional,UniversidadeFederaldoRiodeJaneiro,Brazil.2LaboratóriodeEcofisiologiaeToxicologiadeCianobactérias, IBCCF,UniversidadeFederaldoRiodeJaneiro,Brazil3LaboratórioCentraldaCesama,Cesama,Brazil4Laboratório de Ecologia e Fisiologia do Fitoplâncton, Departamento de Biologia Vegetal,UniversidadedoEstadodoRiodeJaneiro,BrazilIn the tropical eutrophic Funil Reservoir, Brazil, blooms of the cyanobacteriaCylindrospermopsisraciborskii,DolichospermumcircinalisandMicrocystisaeruginosacomplex(MAC) are frequent especially during summer (hot-rainy season) since the 1990s. Recently(2013),thedinoflagellateCeratiumfurcoides,aninvasivespeciesinSouthAmericanfreshwatersystems, was detected for the first time in this reservoir. This study aimed to evaluate thedynamicsofC. furcoides colonization inFunilReservoir.Samplesoccurredduringahot-rainyperiod(October2013toMarch2014)atStation1(closertothetributary)andStation2(closetothedam).Nosignificantspatialdifferencesoftheabioticvariableswasobserved,althoughadecrease in orthophosphate occurred from station 1 to 2 (mean= 10 and 3.5 µg/L,respectively). Low orthophosphate concentrations indicated limitation during most of thestudy.Unlikepreviousobservations,cyanobacterialbloomsdidnotoccurduringthishot-rainyperiod.C.furcoidespresentedhighcontributionstototalphytoplanktonbiovolume(30-90%),withsignificanthigherbiovolumeoccurringatstation2(mean=5.1and10.1mm3/L,stations1and 2, respectively), being dominant there during this whole period.D. circinalis andMACincreasetheircontributionandbiovolumeduringlowprecipitationandhigherretentiontimeperiods. With the increase of precipitation and decrease of retention time, C. raciborskiibiomass increased. Cladocerans, rotifers and nauplii presented a spatial pattern contrary tothe occurrence of C. furcoides, with densities significantly higher at Station 1. Consideringspatialdistribution,theswimmingability,allowingthepursuitofbetternutrientsconditionsindeeperlayers,mightexplainthesuccessandbloomofC.furcoidesatthemorelenticstation2(maximumbiovolume=23mm3/L).Inaddition,thedominanceofthislarge-sized,unpalatabledinoflagellate seemed tohave inhibitedsmallergrazers.These results suggest that the rapidcolonization of C. furcoides in Funil reservoir significantly impacted the local phytoplanktonandzooplanktoncommunities.



41

Seasonalvariabilityandverticaldistributionofchytridparasitesindiatompopulationsinameso-eutrophicreservoir

PavelRychtecký1,PetrZnachor1,JiříNedoma11InstituteofHydrobiology,BiologyCentreofCzechAcademyofSciences,ČeskéBudějovice,CzechRepublic.Parasiticfungiplayoftenimportantroleinmanyaquaticsystemsbyshapingtrophicstructureof planktonic communities. Most parasitic fungi in freshwaters belong to the phylumChytridiomycota(Chytrids),whicharetruefungicharacterizedbyfree-swimmingmotilestages(zoospores). Chytrids that infect phytoplankton are often host specific, highly infective andextremely virulent and canbe adecisive factor in phytoplanktondynamics.We investigatedthe impact of parasitic fungi on populations of common diatoms Asterionella formosa andFragilariacrotonensisinthecanyon-shapedmeso-eutrophicŘímovReservoir(CzechRepublic)duringspringandsummer2016.Tocharacterisechytridinfectionsondiatoms,wecalculatedtwomeasuresofinfection:theprevalenceofinfectionPr(percentageofinfecteddiatomcells)andthemeanintensityofinfectionI(numberofsporangiaperinfecteddiatom).Werecordedtwomaximaof chytridpresence: first during springwhenAsterionella formosawas infectedwithProf15%andsecondduringthesummerwhenhighabundanceofFragilariacrotonensiswas followed by a time-lagged parasite epidemic (Pr = 24 %) resulting in rapid decline ofFragilaria population.During the summerepidemic,we foundpatchy vertical distributionoffungal parasites. The prevalence at the euphotic depth was almost twice as high as at thesurface(40%intheeuphoticdepthcomparedto24%atthesurface).ThemeanintensityofinfectionincreasedwithPrduringthewholeperiodstudied,butthepopulationaverageneverexceed1.5chytridsperhostcell.Inadditiontothefieldsurvey,wereconstructeddataaboutchytrid infections from preserved phytoplankton samples originating from long-termmonitoring of the reservoir. Preliminary results showed that chytrid epidemics occurredfrequentlyyetoftenbeingunnoticed.



42

InvasiveMougeotiafromLakeKinneret:aversatilefilamentousalga

TamarZohary1,UlrikeObertegger2,AllaAlster1,OraHadas11KinneretLimnologicalLaboratory,IsraelOceanographic&LimnologicalResearch,Israel.2ResearchandInnovationCenter,EdmundMachFoundation,Italy.Mougeotiasp.(Zygnematales,Charophyta)appearedintheplanktonofLakeKinneretforthefirst time in June 1998.While initially quite rare, from 2004 onwards it was present in thewater columnmost of the time, forming occasional massive blooms in Spring (2005, 2006,2012) and in late-autumn/early-winter (2010/11). Herewe report on the temporal biomasspattern of this invasive filamentous alga and the environmental conditions supporting itsgrowth. A suite of statistical methods was applied to the long-term record ofMougeotiabiomasstounderstandMougeotia–environmentrelationships.Usingonlyyearandmonthasexplanatorypredictors,generalizedadditivemodeling(GAM)explained36%ofthevariationinMougeotia biomass. However, the temporal dynamics ofMougeotia biomass could not beexplained by any of the environmental parameters considered. Rather, Mougeotia wascapable of growing or at least maintaining its population under a wide range of watertemperatures, nutrient concentrations, solar radiation, pH levels and stratification patterns,indicatingitasahighlyversatilealga.ModellingthetemporaldynamicsofMougeotiabiomassasautoregressiveintegratedmovingaverage(ARIMA(1,0,0)),astrongdensitydependencewasfound.Thus,itseemsthatvariousintra-specificfactors,suchascompetitionfornutrientsandself-shading, play an important role in determining the seasonal and long-termdynamics ofMougeotiabiomass.WespeculatethatLakeKinneretmayhosttwoormorecrypticspeciesofMougeotia,that lookalikeunderthemicroscopebutaregeneticallydistinct;thismayhinderany inference on Mougeotia - environment relationships. This hypothesis remains to beconfirmed.



43

ORGANIZING COMMITTEE

HugoSarmento

VanessaBecker

VeraHuszar

IrinaIzaguirre

CarolinaDavilaDomingues

LucianeOliveiraCrossetti

InésO´Farrell

FernandoUnrein



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LIST OF PARTICIPANTS

Name E-mail António José Calado [email protected] Carla Kruk [email protected] Carolina Davila Domingues [email protected] Claudia Piccini [email protected] Elisa Maria Sol Porcel [email protected] Elżbieta Wilk-Woźniak [email protected] Fabiana Araujo [email protected] Fernando Unrein [email protected] Gábor Borics [email protected] Géza Balázs Selmeczy [email protected] Hugo Sarmento [email protected] Inés O'Farrell [email protected] Irina Izaguirre [email protected] Jean-Pierre Descy [email protected] Judit Padisak [email protected] Kemal Ali Ger [email protected] Kirsten Olrik [email protected] Letícia Barbosa Quesado [email protected] Lúcia Helena Sampaio da Silva [email protected] Luciana de Souza Cardoso [email protected] Luciana Gomes Barbosa [email protected] Luciana Haipek Mosolino Lerche [email protected] Luciana Machado Rangel [email protected] Luciane Oliveira Crossetti [email protected] Luigi Naselli-Flores [email protected] Maria Gabriela [email protected] Maria Leitão [email protected] María Paula Huber [email protected] Mariana Rodrigues Amaral da Costa [email protected] Mariângela Menezes [email protected] Melina Devercelli [email protected] Pavel Rychtecký [email protected] Petar Žutinić [email protected] Petr Znachor [email protected] Rika Muhl [email protected] Rodan Geriš [email protected] Sandra Calado [email protected] Sierra Cagle [email protected] Tamar Zohary [email protected] Vanessa Becker [email protected] Vera Lucia Huszar [email protected] Yonghong Bi [email protected]

Documents

Abstracts IAP preliminary version · 16:00 W.-WOZNIAK DEVERCELLI ZNACHOR IZAGUIRRE Discussion 16:30 SELMECZY O'FARRELL BI OLRIK Session 17:00 Discussion Discussion Discussion Discussion