22nd International diatom symposium Ghent, Belgium 26-31 August 2012: abstracts

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ABSTRACTS
22ndInternationalDiatomSymposium
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Ghent,Belgium
26‐31August2012
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VLIZSPECIALPUBLICATION58
Organizedby:
Lab.Protistology&AquaticEcology   NationalBotanicGardenofBelgium
BiologyDepartmentDomeinofBouchout
GhentUniversityNieuwelaan38
Krijgslaan281,S8B‐1860Meise,Belgium
B‐9000Ghent,Belgiumwww.Botanicgarden.be
www.pae.ugent.be
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ORGANIZINGCOMMITTEE
KoenSabbe,BartVandeVijver,WimVyverman,AnnickVerween,Koenraad
Muylaert,AnnickWilmotte,Jean‐PierreDescy,KateřinaKopalová,Rebeccavander
Wiele,PieterVanormelingen,CarolineSouffreau
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SCIENTIFICCOMMITTEE
KoenSabbe(GhentUniversity,Belgium)
WimVyverman(GhentUniversity,Belgium)
BartVandeVijver(NationalBotanicGardenofBelgium)
KoenraadMuylaert(KULeuven,KULAK,Belgium)
MarieHuysman(GhentUniversity,Belgium)
PeterKroth(UniversityofKonstanz,Germany)
EileenCox(NaturalHistoryMuseumLondon,UK)
RegineJahn(BotanischerGartenundBotanischesMuseumBerlin‐Dahlem,Germany)
AngelaWulff(GoteborgsUniversitet,Sweden)
FrédéricRimet(FrenchNationalInstituteforAgriculturalResearchINRA,France)
ShigekiMayama(TokyoGakugeiUniversity,Japan)
SarahA.Spaulding(UniversityofColorado,Boulder,USA)
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Thispublicationshouldbecitedasfollows:
SabbeKoen,VandeVijverBart&VyvermanWim(Eds).2012Twentysecond
InternationalDiatomSymposium,AulaAcademica,Ghent,26‐31August2012.
Abstracts.VLIZSpecialPublication58,260p.
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Reproductionisauthorized,providedthatappropriatementionismadeofthe
source.
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ISSN1377‐0950
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Contents
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Preface5
Keynotepresentations7
Oralpresentations19
Posterpresentations119
Authorindex253

XXIIInternationalDiatomSymposium
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Preface
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TheLaboratoryofProtistology&AquaticEcology(GhentUniversity)andtheNational
BotanicGardenofBelgiumareproudtowelcomeover210diatomscientistsand
studentstothe22ndInternationalDiatomSymposiuminGhent,August26‐31st2012.
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TheIDS2012programwillhostsessionsonthefollowingthemesindiatomresearch:
DNABarcoding,Biodiversity&Biogeography,EcologyandPhysiology,Ecotoxicology,
EvolutionandPhylogeny,Fossils,MolecularBiology,Morphology,Paleoecology,
TaxonomyandWaterQuality.
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Duringthe22ndInternationalDiatomSymposium,keynotelecturesby9eminent
diatomresearcherswillhighlighttrendsandopportunitiesincontemporarydiatom
science.Inadditionto97abstractswhichwillbegivenasoralpresentations,over
131abstractswillbepresentedaspostersinthreesponsoredpostersessions.
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Wewishallparticipantsapleasantandfruitfulsymposium,
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Theorganizers,
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KoenSabbe
BartVandeVijver
WimVyverman
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XXIIInternationalDiatomSymposium
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KEYNOTE
PRESENTATIONS

XXIIInternationalDiatomSymposium
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XXIIInternationalDiatomSymposium
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DATARICH,INFORMATIONPOOR?10YEARSOFTHEEUWATERFRAMEWORK
DIRECTIVEINEUROPE.
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MartynKelly
BowburnConsultancy
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TheWaterFrameworkDirective(WFD)providesthelegalbasisforwatermanagementin
theEuropeanUnion(EU).Twelveyearsafteritwaspassed,allbutfiveoutof27EU
MemberStatesnowhavephytobenthosassessmentmethodsforrivers,whilstonlynine
havemethodsforlakes.Mostofthesemethodsarebasedondiatoms,althoughafeware
supplementedbyevaluationsofnon‐diatomalgaeandsomestatesincludemacroalgaeas
partoftheirmacrophytesassessmentmethods.Norwayistheexception,havinga
phytobenthosassessmentsystembasedonnon‐diatomalgaealone.Overhalfofallstates
havemethodsbasedwhollyorpartlyonweightedaveragemetricsdevelopedbeforethe
onsetoftheWFD,withninestateschoosingtheIndicedePolluosensibilitéSpecifique.
Thesemetricsgenerallyhavehighcorrelationswiththepredominantnutrient/organic
pollutiongradientfoundacrossEuropeand,assuch,representpragmaticsolutionsto
ecologicalstatusassessment.However,theirwidespreadusealsoraisesquestionsabout
what,exactly,“ecologicalstatus”means.Diatom‐basedmetricsareoftenstrongly
correlatedwithchemicalpressuregradientsyetthismaybeamixedblessing,particularly
whenwemovefromdescribingspatialpatternsofecologicalstatustoprescribingsolutions
forwaterbodiesthatfailtoachievegoodecologicalstatus.Suchpressuregradientsare
oftencomposedofseveralintercorrelatedvariables,makingitdifficulttodisentangle
“correlation”and“causation”intheabsenceofecophysiologicalstudiesofindividual
diatomspecies.Moreover,thefocusonstrongrelationshipswithchemicalgradientsmeans
thatmostphytobenthosmetricsdescribethescaleofhazardatasiteratherthantherisk
thatthehazardposestoothertrophiclevels,andtoecosystemservices.Thisfirst
generationofphytobenthosassessmenttoolsare,atbest,“fitforpurpose”butmaybe
inadequatewhencatchmentmanagersneeddetailedguidanceonremediationsteps
neededforparticularwaterbodies.Asecondgenerationofassessmenttools,focusedon
thefitnessofthephytobenthosaspartofaquaticecosystems,ratherthanjustasindicators
ofchemicalconditions,isneededifthegoalofgoodecologicalstatusaroundEuropeisto
beachieved.
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XXIIInternationalDiatomSymposium
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ASPECTSOFDIATOMMETABOLISM
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PeterG.Kroth
DepartmentofBiology,UniversityofKonstanz
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Algalresearchtodateexperiencesastrongboostfromactualgenomeprojectsandthe
developmentofmoleculartoolstostudyalgaeandalgalprocesses,likelargescale
transcriptionanalyses,transformationtechniquesandgenesilencingapproaches.For
diatomstherearetwogenomespublished(forthepennatesPhaeodactylumtricornutum
andthecentricThalassiosirapseudonana)includingtwomoregenomesclosetopublication
(Pseudonitzschiasp.andFragilariopsiscylindrus).Diatomsareveryinterestingorganismsfor
variousreasons,includingtheirecologicalrelevance,theirsilicifiedcellwallsandtheir
peculiarevolutionviasecondaryendocytobiosis(theincorporationofaeukaryoticalgainto
aeukaryotichostcell,followedbytransformationoftheendosymbiontintoaplastid).
Especiallythelatterprocessresultedinvariousdifferenceswithrespecttothephysiology
andcellbiologyofthesealgaewhencomparedtogreenalgaeandlandplants.Comparative
analysesrevealedrelocatedmetabolicpathways,modifiedregulationprocessesand
unexpectedproteins:
(i)IndiatomsveryfewenzymesoftheCalvincycleareredoxregulatedbysmallproteins
termedthioredoxinsthatfunctionasa“lightswitch”forCO2fixationbyreducingtarget
enzymes.
(ii)Essentialpathwaysliketheoxidativepentosephosphatetogetherwithnucleotide
synthesispathwayshavebeenreallocatedindiatoms.
(iii)Diatomspossessaureacycle.
(iv)DiatomspossessthebacterialEntner‐Douderoffpathway.
(v)Asaconsequence,additionalplastidictranslocatorsfornucleotidesand
carbohydrateswereestablishedtoallowtheessentialtransportoftriosephosphatesas
wellasnucleotidesintoandoutoftheplastids.
(vi)Enzymesofthesecondhalfofglycolysiscanbefoundinthecytosol,intheplastidsas
wellasinthemitochondria.
(vii)Therearefirstindicationsthatenzymesmightbelocatedintheperiplastidicspaceof
diatoms,includinganNADP‐dependentthioredoxinreductaseandaphosphogluconate
dehydrogenase.
(viii)Diatomsalsoshowaveryunusualdistributionofcarboxylatinganddecarboxylating
enzymespossiblyinvolvedinphotosynthesis.
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XXIIInternationalDiatomSymposium
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DIATOM‐BASEDBIOMONITORINGINCANADA:REFLECTIONSON10YEARSOF
DEVELOPMENT,IMPROVEMENTANDPERSUASION
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IsabelleLavoie,StéphaneCampeau&ClaudeFortin
Institutnationaldelarecherchescientifique,CentreEauTerreEnvironnement
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Canadianprovincesandterritorieshavetheprimaryjurisdictionovermostareasof
freshwatermanagementandprotection,andestablishtheirownguidelines,objectivesand
regulationsfollowingtherecommendationsoftheCanadianCouncilofMinistersofthe
Environment.Thesedifferentjurisdictionalroleshaveledtoanumberoflawsandpolicies
specifictoeachprovinceandterritory(eg.,SustainableDevelopmentActinQuébec,Clean
WaterActinOntario,WaterManagementFrameworkinSaskatchewan,etc.).
Alltheseregulationsrequireintegratedwatermanagementsystemswithagoodknowledge
andunderstandingofreferenceconditionsandthedevelopmentofmonitoringtools
indicatingameasureofdeparturefromreferencestate.However,waterqualitymonitoring
inCanadahasmostlybeenbasedontraditionalchemicalmeasurements,andwater
agencieshavebeenseekingnewapproachesallowingforamoreadequatemonitoringof
aquaticecosystemintegrity.Effortshavebeenmade(especiallyinOntarioandQuebec)to
promoteamacro‐invertebratebiomonitoringnetworkforevaluatingaquaticecosystem
conditions.However,althoughmacro‐invertebratesareexcellentgeneralindicatorsof
habitatandwaterqualityatthewatershedscale,macro‐invertebratemonitoringalone
cannotalwaysprovideareliableindicationofeutrophicationandisnotassensitivetowater
qualityfluctuationsasdiatomassemblagesare.
Inspiredbythesuccessofroutinediatom‐basedmonitoringincertainEuropeancountries,a
similarapproachhasbeensuggestedforassessingstreambiologicalintegrityinEastern
Canada.TheEasternCanadianDiatomIndex(IDEC:IndiceDiatoméesdel’EstduCanada)
wasdevelopedalmost10yearsagotomonitorthebiologicalintegrityofstreamsandrivers
inEasternCanada.TheIDECgainedpopularityinEasternCanadaandhasbeenused
successfullytoevaluatethebiologicalstatusofmorethan1500diatomassemblagesover
thepast10years.Theexperiencegainedondiatom‐basedmonitoringovertheyearsaswell
asthelargenumberofsamplesaddedtothedatabaseledtothemodellingofanewversion
oftheIDECin2012.
ThispresentationwillexplainthestepstothecreationoftheIDEC,itsevolutionoverthe
years,andwillalsoexposeourreflectionson10yearsofdiatom‐baseddevelopment,
persuasion,andongoingchallenges.
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XXIIInternationalDiatomSymposium
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AMULTIFACETEDANDINTEGRATEDAPPROACHTOTHESTUDYOFMARINE
PLANKTONICDIATOMS

MarinaMontresor
StazioneZoologicaAntonDohrn
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DiatomsrepresentthemostabundantphytoplanktongroupattheLTERMareChiarainthe
BayofNaples(MediterraneanSea);theydominateduringthespringandautumnblooms
andproduceminorbloomsduringsummerstratification.Detectionofmicroalgal
distributionpatternsreliesonthebiologicalunits(species,populations).Resultsofour
researchuncoveredcrypticdiversityinallgeneraexamined:Skeletonema,Pseudo‐nitzschia,
ChaetocerosandLeptocylindrus.Thesefindingschallengedourcapabilitytomonitorspecies
withstandardtechniques,demonstratingtheneedformoleculartoolssuchasclone
libraries,microarrays,metagenomicapproaches.Ontheotherhand,detectionofcryptic
diversityclarifiedtemporalandspatialpatternsinmorphospecies.Analysisof
environmentalsamplesusingclonelibrariesofpartialLSUrDNAconfirmeddistinctseasonal
patternsindifferentPseudo‐nitzschiaspecies.InSkeletonema,analysisofglobalisolates
showedspecies‐specificdistributionranges,challengingtheassumptionthatphytoplankton
specieslackbiogeographicstructure.Thisbroaddiversitycallsforintegratedapproaches
towardsdelineatingspecies,includingassessmentoffunctionaldifferences.Screeningof
Pseudo‐nitzchiamultistriatapopulationstructurewithmicrosatellitesshowedmarked
intraspecificdiversityandprovidedevidencethatgeneticallydifferentmetapopulations
coexistinsympatry.Moreover,microsatelliteprofilesinculturevaryovertime,suggesting
thatthehighgeneticdiversitydependsonrapidaccumulationofclonalmutationsand
geneticrecombinationduringsexualreproduction.
Lifecycletraitsofmicroalgaealsoplayanimportantroleinregulatingthedynamicsof
naturalpopulations.ManydiatomsatLTER‐MCformrestingstages,butinteractions
betweenvegetativeandrestingstagesarecomplexandlinksbetweentheonsetofspecies‐
specificbloomsandthegerminationofrestingstagesisdifficulttoassess.Inspeciesthatdo
notformrestingstages,gradualreductionandsuddenincreasesincellsizesshedlighton
timingforasexualandsexualphases.AnalysisofcellsizedistributionpatternsofPseudo‐
nitzschiamultistriatacoupledwithmodelingapproachesshowedthatthelengthoflifecycle
–fromtheinitialcellstothesmallestcellsize‐lastsabout4years;ifsexualreproduction
doesnottakeplace,thepopulationiscondemnedtolocalextinction.
Populationdynamicsrepresentstheinterplaybetweentheorganisms’complexlifehistories
andtheirenvironment.The‘observation’ofnaturalpopulationsovertimeandspace,the
couplingwithexperimentalapproaches,andadeeperunderstandingoftheorganism
biology–nowpossiblewithgenomicapproaches–allowsprogressinelucidatingtheir
complexdynamics.


XXIIInternationalDiatomSymposium

~13~

LIFEINAGLASSHOUSE:FROMCELLWALLMORPHOGENESISTO
NANOTECHNOLOGICALAPPLICATIONS

NicolePoulsen
BCube:CenterofInnovativeCompetenceforMolecularBioengineering,TUDresden
Thediatomcellwallstructureisaspecies‐specificcharacteristicdemonstratingthatits
morphogenesisisgeneticallyencoded.Understandingthemolecularmechanismsbywhich
asinglecellexecutesthemorphogeneticprogramfortheformationofaninorganicmaterial
(biomineralization)isnotonlyafascinatingbiologicalproblem,butalsoofgreatinterestfor
nanomaterialsscienceandtechnology.Recently,diatomgenomesequencingprojectshave
providedtheopportunitytoidentifytheentiresetofproteinsinvolvedinsilicaformation.
Althoughsubsequenttranscriptomicsandproteomicsanalysesprovidedhundredsof
potentialcandidateproteinstheyhavefailedtoidentifyalreadyknownsilicaforming
proteins.Thishasraisedconcernsregardingthespecificityandsuitabilityofsuchhigh‐
throughputmethodsforstudyingdiatomsilicaformation.InthispresentationIwilldescribe
theresultsthatwehaveobtainedusinganentirelydifferentapproach.Thegenome
databaseofthemodeldiatomThalassiosirapseudonanawasscreenedinsilicoforproteins
containingdomainsthatmimictheaminoacidcompositions(ratherthansequence)ofsilica
formingproteins.Thescreenretrievedtheknownsilicaformingproteinsinadditionto86
otherproteins,ofwhichmostdidnotexhibitsequencehomologytoanyproteinsfrom
otherorganisms.Amongthesediatom‐specificproteinsaresixproteins,whichwedenoted
cingulins,thatexhibituniqueandhighlyrepetitiveaminoacidsequencemotifs.Subsequent
invivofunctionalanalysisofcingulinsresultedintheidentificationofapreviouslyunknown
yetapparentlygeneralprinciplefordiatomsilicamorphogenesis.Inthefinalpartofmytalk
Iwilldemonstratehowtheemerginginsightintothemolecularmechanismofdiatomsilica
formationhasenabledthedevelopmentofanentirelybiologicalmethodfortheproduction
ofnanopatternedsilicawithdesiredcatalyticactivities.




XXIIInternationalDiatomSymposium

~14~

METAGENOMICS:FROMPARTSLISTSTOECOLOGY

JeroenRaes
VIBDepartmentofStructuralBiology
Meta‐omics(metagenomics,metatranscriptomics,metaproteomics)arepowerfultoolsfor
theanalysisofthe(unculturablefractionof)microbialcommunities.Becauseofits
complexity,meta‐omicsdatahasrequiredthedevelopmentofnovelcomputationalanalysis
toolstodeterminethefunctionalandphylogeneticcompositionofthesampledcommunity
(Raesetal.,CurrOpinMicrobiol2007).
However,togofromametagenomic‘partslist’(i.e.abagofgenes)toaninitial
understandingoftheecosystemstructureandfunctioning,currenttoolsarenotsufficient
(Raes&Bork,NatRevMicrobiol2009).Iwillpresentarangeofapproachestoanalyze
metagenomes,inferecologicalparameters,extractspeciesinteractionandcompetition
relationships,interpretmetabolicchangesandidentifybiologicallyrelevantfeaturesfrom
meta‐omicsdatawithapplicationsindiverseenvironments.Iwillspecificallyfocusondata
comingfromtheTaraoceansexpedition,integratingmulti‐omicsapproacheswithdetailed
oceanographicmeasurementsfromvirusestofishlarvae.


XXIIInternationalDiatomSymposium

~15~

TRADITIONALTAXONOMYINTHEMOLECULARAGE:CONTROVERSIESOR
SYNERGIES?

RosaTrobajo
AquaticEcosystems,InstituteforFoodandAgriculturalResearchandTechnology(IRTA)

Asoundspeciestaxonomyofdiatomsisofparamountimportance,amongotherreasons
becauseeverythingelse–ecology,biogeography,evolution,stratigraphy,palaeoecology,
biomonitoring,biotechnology,etc(allofwhicharerapidlyexpanding)–isunderpinnedby
ourabilitytoidentifyspeciesandlinkdatatogetherviaspeciesnames.Theintroductionof
moleculardataintodiatomtaxonomyhasledtomuchdiscussionandevensome
antagonism.Attheirmostextreme,opposingattitudescouldperhapsbecaricaturedas(1)
morphologyisunreliable,subjectiveandshouldbeabandonedasasourceofdataand
replacedbymodernmoleculartechniques;versus(2)themolecularapproachisfulloffake
promisesaboutimprovements,andallithasdonesofarisrevealhighgeneticdiversity
whoserelevance(ifany)isunknown.However,increasinglythereareexamplesthatshow
thatmultiplesourcesofdata(e.g.morphologicalandmolecularbutalsophysiological,
reproductivebehaviour,etc)providedifferentbutcomplementaryinsightsintospecies
delimitationandidentification.Toillustratethis,Iwillmainlyuseourworkonsome
Nitzschiasect.Lanceolataespecies,butIwillalsomakereferencetootherdiatomsfrom
timetotime.Nitzschiaisalargegenus,notoriousforitstaxonomicdifficulty,andmembers
ofthesect.Lanceolataeareparticularlychallenging,becausemosthavesmallcellsand
delicatestructure,andbecausetheyofferfewdiagnosticcharacters.However,these
difficultiesneedtobeovercome,forinstancebecausetheLanceolataeareofgreatt
importancefromthe(palaeo‐)ecologicalpointofview:theyoccurfrequentlyand
abundantlyinallkindsofwaters,andseveralofthemareconsideredtobeindicatorsof
particularenvironmentalconditions.Iwillexplainhowwehaveusedcultureexperimentsto
investigate1)howphenotypicplasticity(e.g.inrelationtosalinity)affectsthereliabilityof
morphologicalcharactersfortaxonomy,2)morphologicalchangesassociatedwiththelife
cycle,3)reproductivebiology,and4)ecophysiology,andIwillthenexplorehowthese
resultscanbeintegratedwithmolecularphylogeneticdata.Finally,Iwillprovideabrief
evaluationofthecurrentstatusofDNA‐basedbarcodingindiatomsanditspotentialand
limitationsinfuturecharacterizationsofdiatomcommunities.




XXIIInternationalDiatomSymposium

~16~

LIFEONTHEEDGE:HOWINTERTIDALBENTHICDIATOMSTHRIVEINCOASTAL
ENVIRONMENTSANDWHYWESHOULDCARE'

GrahamJ.C.Underwood
SchoolofBiologicalSciences,UniversityofEssex

Goldenbrownpatchesofcolouronthesurfaceofintertidalmudflatsandsandflatsarethe
signsofabundantpopulationsofmicrophytobenthicdiatoms.Species‐richand
physiologicallyversatile,theseintertidalassemblagesnicelyillustratesomeofthekey
advantagesoflivinginbiofilms.Biofilmsarethreedimensionalstructures,withcellsheld
withinamatrixofsedimentparticlesandextracellularpolymericsubstances(EPS).
Irradiancelevelsatthebiofilm’ssurfacecanbeextremelyhigh,anddifferentspeciesof
microphytobenthicdiatomshowdistinctmigratorybehaviour,inresponsetolight
gradients,anduseverticalmigrationwithinthebiofilmasamechanismof
photoacclimation,combinedwithphysiologicalresponsestodealwithlightstressand
desiccation.Changinglightandnutrientconditionsalsomediatepatternsofproductionof
differentEPSfractionswithinbiofilms,andEPSservesbothaprotectiveandnutritional
functionforbenthicdiatoms.Diatomspeciescompositionisalsoinfluencebynutrients,
spatialdistributionandenvironmentalfactorssuchasanoxiaanddisturbance,andhasthe
potentialtofeedbacktoeffectbiofilmproperties.Allthesefactorsresultinaninterplay
betweenspeciesrichness,abundanceandecosystemfunctioning.Highratesofproduction,
nutrientuptakeandoxygenproductionmeanthatestuarinebiofilmsplayinganimportant
roleinthebiogeochemistryandecologyofshallowestuarineandcoastalwaters.
Quantifyingandunderstandingdiatombiofilmprocessesisanecessarycomponentforgood
managementofimportantcoastalecosystems.


XXIIInternationalDiatomSymposium

~17~

DIATOMDISTRIBUTIONSINSPACEANDTIME–ACASESTUDYFROMTHE
POLARREGIONS

ElieVerleyen
LaboratoryforProtistology&AquaticEcology,DepartmentofBiology,GhentUniversity

Thecomposition,diversityanddistributionofpresent‐daybiotaareshapedbythe
geological,tectonicandclimaticpast,whichresultedinthedistinctbiogeographicalrealms
weobserveintheterrestrialbiosphere.HereIsummarizeourrecentstudiesonthe
biogeographyofpolarfreshwaterdiatoms.Antarcticlake‐dwellingdiatomcommunitiesare
impoverishedandimbalancedincomparisonwithArcticcommunities,andcharacterizedby
highlevelsofendemism.Moleculardataonubiquitousmorphospiecesthatarewidespread
intheAntarcticregionarestartingtorevealsubstantialhiddendiversity,withdistinct
Antarcticandsub‐Antarcticlineages.Thissuggeststhatestimatesbasedonthe
morphospeciesconceptareconservativeandmaystronglyunderestimatetheobserved
levelsofendemism.TheAntarcticcommunitiesarefurthercharacterizedbytheabsenceof
keyfunctionalgroupssuchasplanktonictaxa,ageneralpaucityofgloballysuccessful
genera,andanoverrepresentationofterrestriallineages.Comparisonofcontemporary
AntarcticfloraswithfossilMioceneassemblagespointstohighratesoflocalextinction
duringglacialmaxima,incombinationwithradiationsandtheselectivesurvivalofaerophilic
taxainglacialrefugia.Wealsoobservedstrongbioregionalisationpatternswithinthe
AntarcticRealm,whicharehighlyconcordantwiththethreemainbiogeographicalregions
traditionallyrecognizedinplantsandanimals,namelySub‐Antarctica,MaritimeAntarctica
andContinentalAntarctica.WithinContinentalAntarctica,theobservedbiogeographic
provincialismislikelyrelatedtodifferencesintheglacialhistoryoftheice‐freeregions.
SedimentrecordsspanningtheLateQuaternaryperiodindicatethatlakedistrictswhich
escapedcompleteglacialoverridingduringtheLastGlacialMaximum(LGM)holdarelict
diatomflora,composedofAntarcticendemicsandubiquitoustaxathatinhabitcold
environmentselsewhere.Bycontrast,inregionsthatwerecompletelyoverriddenbythe
EastAntarcticIceSheet,thediatomcommunitiesarecomposedofaerophilicAntarctic
endemicsandubiquitoustaxa.Thesetaxawereprobablyderivedfromalocaldiatompool
thatwasabletosurviveinlocalterrestrialnunataks.Thisisconfirmedbyatime‐constrained
molecularphylogenyoftheaerophilicdiatomPinnulariaborealiswhichsuggeststhatthe
Antarcticlineagediverged7.8(2‐15)Maago,andhencebeforetheonsetofPleistocene
glacial‐interglacialcycles.Inaddition,thereisevidenceforlarge‐scaleextinctionsduringthe
LGMofspeciescurrentlythrivinginSub‐Antarctichabitatsbutwhichwerepresentin
ContinentalAntarcticaduringthewarmerEemianinterglacial.

XXIIInternationalDiatomSymposium
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XXIIInternationalDiatomSymposium
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
ORAL
PRESENTATIONS
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XXIIInternationalDiatomSymposium
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~20~
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XXIIInternationalDiatomSymposium
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~21~
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LARGE‐SCALEMORPHOLOGICALCONVERGENCECOINCIDESWITHREPLICATE
RADIATIONSOFDIATOMSINTOFRESHWATERS

AndrewJ.Alverson
UniverstiyofArkansas,DepartmentofBiologicalSciences

Salinityrepresentsasubstantialbarriertothedistributionofdiatomsandotheralgae.A
phylogenyoftheThalassiosiralesrevealedmultipleindependentfreshwatercolonization
events,twoofwhichledtomajorevolutionaryradiations.Thesetwolineagessharea
numberofindependentlyderivedphenotypes,includingthickenedcostae,marginal
chambers,andseveralstruttedprocesscharacters.Comparativeanalysesshowastrong
correlationbetweentheevolutionofthesetraitsandtheiroccurrenceinfreshwatertaxa,
providingcompellingevidencethattheconvergenttraitsconfersomeadaptivevaluetolife
infreshwaters.
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XXIIInternationalDiatomSymposium
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~22~
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APPLICATIONOFNEWFLUORESCENCE‐TAGGEDAMINESANDPOLYMERSIN
STUDYOFDIATOMPHYSIOLOGY

VadimV.Annenkov,TatjanaN.Basharina&ElenaN.Danilovtseva
LimnologicalInstituteoftheSiberianBranchoftheRussianAcademyofSciences

Wepresenttheresultsofthegrowthofthefresh‐waterdiatomSynedraacussubsp.radians
(Kützing)Skabichevskiiinthepresenceofnewfluorescence‐taggedaminescontainingone
ortwotertiaryaminemoietiesandhigh‐molecularpolymerswithcarboxylic,amineand
imidazolegroups.Thefollowingobservationsandconclusionshavebeenmade:
‐Poly(acrylicacid)(PAA)bearingfluorescencegroups(onegroupperchain)wasfoundin
silicafrustulesafterS.acusgrowthinthepresenceofPAA.Non‐taggedPAAwasalso
detectedinthefrustulesafterremovingoforganiccomponentsofthecellsSuchneutral
polymeraspoly(1‐vinylimidazole)andpositivechargedpoly(vinylamine)arenotincluded
intothefrustules.WeconsiderthisbehaviourofPAAisexplainedwith(macro)pinocytosis
hypothesis[VrielingE.G.etal.PNAS104:10441].Themostprobablecytoplasmicformof
siliconisslightlycondensedsilicicacid[AnnenkovV.V.etal.Biomacromolecules12:1772]
andPAAissimilarwithpoly(silicicacid)inacidity,sowecansupposethatduringsome
stagesofsiliconassimilationthediatomcelldoesnotdiscriminatethesesubstancesand
PAApenetratesintogrowingvalves.
‐Fluorescence‐taggedshort‐chainaminespenetrateintothediatomcellandstainnew
frustulessimilartotheknownlisotrackersPDMPOandHCK‐123[J.Desclésetal.New
Phytol.177:822].Formationofdyedsubmicroncytoplasmicvesicleswasobservedonthe
firststageofnewvalvegrowth.Thesevesiclesdisappearaftertheformationofatwo‐
dimensionalvalve,whichtakes5–10minforindividualcells.Furtherformationofthe
three‐dimensionalvalvestructuretakes10–12h,followingwhichcelldivisionoccurs.We
speculatethatthesmallcytoplasmicvesiclesobservedarerelatedtosilicicacid
assimilationviaa(macro)pinocytosismechanismwhichcouldtakeplaceonthefirst
stageofthevalveformation.
‐Fluorescence‐taggedshort‐chainaminesareusefulsubstancesformonitoringprocesses
indiatoms.Wehavefoundthattheintroductionofthedyesintoasynchronizedculture
undersiliconstarvationisagoodwaytoestimatefractionofcellsstoppedinG2phase
(synthesisofnewvalves)–thesecellscontainstainablevesiclesasopposedtogood
synchronizedcells.TheabilityofnewdyestostainSDV(SiliconDepositionVesicle)was
usedtomonitorsplittingofdiatomfrustulesundertheactionofterahertzlaser
irradiation.Wehavefoundthatthisirradiationallowstoremovesiliconvalvesfromthe
organicmembranewithoutdeteriorationofchloroplastsandSDV.

ThestudywaspartiallysupportedbyProject#11‐04‐00707‐aoftheRussianFoundationfor
BasicResearch.


XXIIInternationalDiatomSymposium
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~23~
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CELL‐STATETRANSITIONSINTHEDIATOMTHALASSIOSIRAPSEUDONANA
DURINGDIURNALGROWTH

JustinAshworth1,SachaCoesel1,AllisonLee1,E.VirginiaArmbrust2,MónicaV.Orellana1,2&
NitinS.Baliga1,2
1InstituteforSystemsBiology
2UniversityofWashington

Diatomsareimportantprimaryproducersinmarineecosystemswhosesuccessdependson
theregulationoftheirphysiologicalstatesunderchangingenvironments.Wehave
conductedagenome‐widesurveyofthediatomThalassiosirapseudonanaduringgrowthat
twomoderateCO2levels.Thisrevealslarge,reproduciblecell‐statetransitionsbetweenfour
principalconditions:I)exponentialandnutrientreplete,II)stationaryandnutrient
depleted,III)darkandIV)lightphasesofgrowth.Herewepresentagene‐level
characterizationofthesephysiologicalmodes,includingpatternsofdifferentialexpression
inmetabolism,nutrientassimilation,andmultiplelevelsofcellularregulation(transcription
factors,chromatinmodifyingenzymes,andsignalingandsensoryproteins).Theco‐
expressionofthousandsofknownandunknowngenesofunderspecificphysiologicaland
environmentalcontextsprovidescluesintotheirfunctionsandbiologicalregulation.Thisis
importantforthediatomclade,inwhichmostofthegenesthatarepredictedand
expressedareofunknownfunction.Physiologicalstatesandtransitionsthatareconsistent
atbothambientandelevatedpCO2arerelevanttodiatomecophysiologyinachanging
climate,andwillfacilitatefurtherannotation,hypothesisgeneration,andtheinterpretation
ofdatacollectedinthefield.
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XXIIInternationalDiatomSymposium
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~24~
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TESTINGTHEGENERICLIMITSOFTHEBIDDULPHIACEAE
(BACILLARIOPHYCEAE):REVISITINGROSS&SIMS(1971)WITHMOLECULAR
DATA

MattP.Ashworth1,T.Nakov1&E.C.Theriot2
1SectionofIntegrativeBiology,UniversityofTexasatAustin
2TexasNaturalScienceCenter,UniversityofTexasatAustin

TheocellateandpseudocellatediatomsintheBiddulphiaceaearedistinctiveandhavearich
fossilhistory,makingthemcommoncomponentsofmarinecoringstudiesandgood
candidatesformoleculardatingwork.Also,thesediatomsareimportanttounderstanding
thephylogenyofthediatomsasawhole,sincethedistinctionbetweenthearaphidpennate
andmultipolarcentricdiatomshasbecomeblurredbytheincreaseduseofmolecular
markers.However,theconvolutedtaxonomichistoryofthesegroupshasthepotentialto
disruptbothtypesofstudies,asmanytaxastillhavemultiplegenericdesignationsthatare
commonlyusedintheliterature.In1971,RossandSimsusedscanningelectronmicroscopy
toexaminevalvecharactersofseveralocellateandpseudocellatediatomsandcameup
withaschemeofmorphologicalcharactersthatcoulddefinethesegenera.Inthisstudy,we
usedmolecularcharacters(nuclear‐encodedSSUrRNAandplastid‐encodedrbcLandpsbC)
totestifRossandSims’morphologicalcharactersaresynapomorphicwithrespecttothe
diatommolecularphylogeny.Whilesomemorphologicalcharactersdoindeedappeartobe
synapomorphic,othersdonot.

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XXIIInternationalDiatomSymposium
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~25~
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SPATIO‐TEMPORALDYNAMICSOFMICROPHYTOBENTOSINTHETAGUS
ESTUARY(PORTUGAL)DETECTEDBYSPATIALREMOTESENSING

LaurentBarillé1,AnaBrito2,IsmaïlBenyoucef1,BrunoJesus1,2,VonaMéléder1,P.Gernez1,
PatrickLauneau3&VandaBrotas2
1UniversitédeNantes,InstitutUniversitaireMeretLittoral,EA2160MerMoléculesSanté
2CO‐FCUL,CentrodeOceanografia,FaculdadedeCiêncasdaUniversidadedeLisboa,
3UniversitédeNantes,InstitutUniversitaireMeretLittoral,UMRCNRS6112Laboratoirede
PlanétologieetGéologiedeNantes

Benthicmicroalgaecanmakeasubstantialcontributiontothefoodwebincoastal
ecosystems,inparticulardiatoms,whichdominatephoto‐autotrophicassemblagesin
intertidalmudflats.Theyformdensebiofilmsinthemostsuperficialsedimentlayersand
contributetotheirstabilization.Manystudiesinvestigatedthespatio‐temporaldynamicsof
thesebiofilmsatmicroscale(below1m2)usingcoringtechniquestosamplesurfacesoften
smallerthan20cm2.However,thevalidityofmicroscalesamplingprotocolsusedtoinfer
spatialstructuresatmacroscaleortoanalysetemporalpatternsofmicrophytobenthos
biomassisquestionable(Spilmontetal.2011).
Inthisstudy,weanalyzedspatio‐temporalvariationsofbenthicdiatombiofilmsatthe
macroscaleoftheTagusestuary(Portugal),oneofthelargestestuarinesystemsinwestern
Europe(38°44’N,9°08’W),usingSPOTmultispectralsatelliteimages.Theintertidalflats
(meantidalamplitudeof2.6m)aredominatedbymuddysedimentandrepresent128km2.
SPOTHRVsensorischaracterizedbyalowspectralresolution(3broadspectralbandsofca.
100nm)butahighspatialresolutionwithpixelsizerangingfrom10x10mto20x20m.The
NormalizedDifferenceVegetationIndex(NDVI)involvingredandnearinfrared(NIR)bands:
NDVI=(NIR‐red)/(NIR+red),wasusedtodiscriminatebenthicmicroalgaefromtheother
benthicphotoautotrophs:angiospermsofthesaltmarshesintheupperintertidalor
macroalgaeattachedtodeadoystershellsinthelowerintertidal.Thespatialdistributionof
microphytobenthosshowedthatthemainassemblagesweredetectedintheupper
intertidalflats(+3to+5mabovethelowestatronomicaltide)withadecreasetowardthe
lowestbathymetriclevels.Thetemporaldynamicwasanalysedwith5imagescoveringa
seasonalcycle.NDVItime‐seriesrevealedastrikingseasonalvariation,withhighNDVI
valuesinwinterandlowNDVIvaluesinsummer.Thisresultistheoppositeofthepattern
detectedinnorthEuropeanestuarieswithMODISsatelliteimages(vanderWaletal.2010).
Asignificantempiricalrelationshipwasobtainedbetweenanextensivemicrophytobenthos
biomassdatasetcollectedinthetopmillimetres(2‐5mm)ofthesedimentduringwinterin
situcampaignsandNDVIvaluesretrievedfromasynchronoussatelliteimage.This
relationshipwasusedtoobtainabiomassdistributionmap(mgchlorophylla.m2)thatwas
comparedwithothermicrophytobenthosbiomassdatameasuredintheTagusestuary.


XXIIInternationalDiatomSymposium

~26~

PHOTOPROTECTIONCAPACITYDIFFERSAMONGMICROPHYTOBENTHIC
DIATOMSINHABITINGINTERTIDALMUDFLATS:POSSIBLECONSEQUENCESON
THEIRSPATIALDISTRIBUTIONRELATEDTOTHELIGHTENVIRONMENT

AlexandreBarnett1,VonaMéléder2,LanderBlommaert3,PierreGaudin2,WimVyverman3,
KoenSabbe3,ChristineDupuy1&JohannLavaud1
1UMR7266LIENSs,InstitutduLittoraletdel’Environnement,CNRS/UniversitédeLaRochelle
2UPRESEA2160‘Mer,Molécules,Santé’,UniversitédeNantes
3LaboratoryofProtistologyandAquaticecology,DepartmentofBiology,GhentUniversity

Coastalecosystemsareoneofthemostproductiveareasintheworld.Theirproductivityis
mainlysupportedbythemicrophytobenthos(MPB)whichinhabitsestuarineintertidal
mudflats.MPBismainlydominatedbydiatomsthatcandivideinthreemainfunctional
forms:1)motilethroughthesediments/biofilm‐formingatthesurface;mainlyunmuddy
mudflats,2)attachedtothesediments(stalkedandadnate);mainlyinsandymudflats,3)
tychoplanktonic(theyneedtospendpartoftheirlifecycleresuspendedinthewater
column)inallhabitats.Thelightenvironmentinintertidalmudflatsisstronglyvariableso
thatMPBcanexperienceveryextremelightclimatesintermsofintensityandlight
fluctuations(amplitude,frequency).Diatomshaveevolvedphysiologicalprocessesinorder
toacclimatetothelightenvironmentandespeciallytoresisttoexcessstressfullight
conditions.Amongtheseso‐calledphotoprotectiveprocesses,thephotosystemIIelectron
cycle(PSIICET),thenon‐photochemicalquenchingofchlorophyllfluorescence(NPQ)and
theassociatedxanthophyllcycle(XC)arebelievedtobethemostimportantones.Thetwo
aimsofthisstudyweretogaininsight1)onthepotentialphotoprotectiveabilityofthe
threefunctionalformsofMPBdiatoms,2)ontheirabilitytoresisttoalightstressandto
maintainphotosynthesisperformancesundersuchconditions.Weperformedascreening
on15species(7motile,3adnate,3stalked,2tychoplanktonic)isolatedfromdifferent
ecosystems(AtlanticcoastandNorthSea).WemeasuredthePSIICET,NPQandtheXC
extentandkineticsbyperforminglightcurvesofdifferentintensitiesuptofullsunlight
(2000µmolphotonsm‐2s‐1).Weespeciallyobservedthatattacheddiatomsshowahigher
NPQaswellasahigherPSIICETcapacityindependentofstalkedandadnateforms.In
contrast,themotiletychoplanktonic(growninbenthicmode)formsshowedalowerPSII
CETandNPQ.Interestingly,theNPQabilityisnotdirectlyrelatedwiththeextentoftheXC.
TheseresultswillbediscussedasregardstotheMPBability/inabilityformotilitythrough
thesedimentandthephysicalpositioningofthediatomcellsatanoptimumleveloflight
forphotosyntheticproduction,i.e.arethemotileformsshowingalowerphysiological
photoprotection(PSIICET,NPQ,XC)becausetheycanexertbehaviouralphotoprotection
(so‐called‘migration’)incontrasttotheattachedforms?


XXIIInternationalDiatomSymposium

~27~

THEROLEOFDIATOMCOMMUNITIESINTHEQUALITYEVALUATIONAND
ECOLOGICALCHARACTERIZATIONOFAREGULATEDMEDITERRANEANSTREAM

MaurizioBattegazzore1,LucioLucadamo2&LuanaGallo2
1ARPAPiemonte,DipartimentodiCuneo
2DipartimentodiEcologia,UniversitàdellaCalabria

In2005,astudywasconductedonthediatomcommunitiesoftheR.Mucone,aregulated
MediterraneanstreaminamountainouspartofCalabria(S.Italy).Diatomsweresampledin
4locationssituatedatincreasingdistancesfromthedamwhichformsLakeCecitaandin
other3locationsalongunregulatedtributaries.Threesamplingcampaignswere
undertaken,inthecourseofwhichaquaticchemical‐physicalfactorsandstream
morphometriccharacteristics.Physicalsubstratewascharacterized,andseveralwater
chemistryvariableswereanalyzedinallstations.
Atotalof97taxawereidentified.ThemostabundantwereAchnanthidiumminutissimum
(23.5%ofidentifiedindividuals),Cocconeiseuglypta(9.6%),Cocconeispseudolineata(7.2%),
A.pyrenaicum(6.9%),Fragilariacrotonensis(3.9%),Naviculagregaria(3.8%)andalesswell
knownspecies,Adlafiasuchlandtii(3.6%).
ADetrendedCorrespondenceAnalysis(DCA)onthetaxonomicdataofthe15most
abundanttaxapreliminarilyallowedtodistinguishdifferentgroupsofsamples:afirstgroup,
withacertaindegreeofinternaldifferentiation,whichincludedthefirst3stationsalongthe
R.Muconedownstreamofthedamandagroupincludingthesamplestakeninthefinal
stationalongtheR.Muconeandinthreereferencesitessituatedalongthetributaries.A
ClusterAnalysis(CA)andaMulti‐ResponsePermutationProcedure(MRPP)alsoconfirmed
thesegregationofthesegroupsofsamples(andsites).Severaldiatom‐basedwaterquality
indiceswerecalculated.
Thementionedgroupsofstationsshoweddifferencesincommunitystructure.Inparticular,
inthosedownstreamofthedamthemostabundantspecieswasA.minutissimum(33.9%of
individualsidentified),C.euglypta(15.5%)andF.crotonensis(8.6%),whileinthegroupof
referencesitesincludingthemostdownstreamstationoftheR.Muconethe3most
abundantspecieswereA.minutissimum(15.3%ofindividualsidentifiedinthisgroup),
C.pseudolineata(12.6%)andA.pyrenaicum.(12.3%).A.suchlandtiiwasfoundonlyinthe
groupofreferencestations.Severalspeciesshowedstrongdifferencesinaverage
abundancebetweensegregatedgroupsofsamples.
Thedifferencesbetweenthegroupsofsamplescanbeexplainedprimarilybythepresence
ofthedamanditsinfluenceonthehydrologydownstream.Thefinalstationalongthe
R.Muconeappearedtobemoresimilartothereferencesites,indicatingasignificantdegree
ofrecovery,thankstotheincreasingdistancefromthedamandtotheeffectofthe
tributaries.
Theresultsprovedtheexistenceofdifferencesamongsitesascribabletotheeffectsofthe
dam.Diatoms,withotherecologicalandenvironmentalvariables,provedtobeausefultool
intheevaluationoftheeffectsofstreamregulation.


XXIIInternationalDiatomSymposium

~28~

CANDIGITALIMAGINGFLOWCYTOMETRYREPLACEMICROSCOPE
MEASUREMENTSOFDIATOMCELLDIMENSIONS?

RebeccaJ.Bixby1,SarahA.Spaulding2,3,DavidH.Jewson4&HarryNelson5
1DepartmentofBiologyandMuseumofSouthwesternBiology,UniversityofNewMexico
2UniversityofColoradoINSTAAR
3U.S.GeologicalSurvey
4FreshwaterLaboratory,UniversityofUlster
5FluidImagingTechnologies,Inc.

Sizeanalysisofdiatompopulationsisapotentiallypowerfultoolforunderstandingdiatom
lifehistories,populationdynamicsandphylogeneticrelationships.However,measuringcell
dimensionsonalightmicroscopeisatimeconsumingprocess.Analternativetechniquehas
beendevelopedusingdigitalflowcytometryonaFlowCAM®(FluidImagingTechnologies,
Inc.)tocapturehundreds,oreventhousands,ofimagesofachosentaxonfromasingle
sampleinamatterofminutes.Uptothirtymorphologicalmeasuresmaybequantified
throughpost‐processingofthehighresolutionimages.WeevaluatedFlowCAMsize
measurements,comparingthemagainstmeasurementsfromalightmicroscope.Wefound
goodagreementbetweenmeasurementofapicalcelllengthinspecieswithelongated,
straightvalves,includingsmallAchnanthidiumminutissimum(11‐21µm)andlarge
Didymospheniageminata(87‐137µm)forms;however,ataxonwithcurvedcells,Hannaea
baicalensis(37‐96µm),showeddifferencesof~4µmbetweenthetwomethods.
Discrepanciesappeartobeinfluencedbythechoiceofferetorgeodesicmeasurementfor
asymmetriccells.Usingexamplesfromthethreetestspecies,boththebenefitsand
limitationsofthisnewtechnologywillbediscussed.Theincreasedspeedofdataacquisition
throughuseofimagingflowcytometersliketheFlowCAMisanessentialstepforadvancing
studiesofdiatompopulations.



XXIIInternationalDiatomSymposium

~29~

MORPHOLOGYANDTAXONOMYOFFOURSPECIESOFTHEMARINE
PLANKTONICDIATOMGENUSBACTERIASTRUM(BACILLARIOPHYTA)FROMTHE
ADRIATICSEA

SunčicaBosak1,DianaSarno2,LukaŠupraha1,DeepakNanjappa2,WiebeKooistra2&Damir
Viličić1
1UniversityofZagreb,FacultyofScience,DivisonofBiology
2StazioneZoologicaAntonDohrn

ThemultipolarcentricdiatomgenusBacteriastrumShadbolt(Chaetocerotaceae)aboundsin
thephytoplanktonofwarmandtemperateseas.Thegenuscomprisesc.12‐15valid
species,belongingtotwosections,Isomorpha,andSagittata,respectivelycharacterizedby
havingthesetaeoftheterminalvalvesmorphologicallysimilarordifferentfromthoseof
theposteriorterminalvalve.Sincethenumberofvalidtaxaisstilldebated,are‐
examinationofthespeciesispresentlyneededaswellastheverificationofthecharacters
supportingtheinterspeciesdistinctionandtheverycircumscriptionofthegenus.Inthe
study,fourcolonialspeciesfromtheAdriaticSea,B.furcatumShadbolt,B.mediterraneum
Pavillard,B.hyalinumLauderandB.jadranumGodrijan,MaricetPfannkuchen,were
investigatedusingbothculturesandnaturalsamples.Thespecieswerestudiedindetail
withlightandelectronmicroscopyandcomparedintermsofthegeneralmorphology,
ultrastructure,andmolecularphylogeny.Phylogeneticanalysisof28S(LSU)sequences
resultedintwoclades,placingtogetherB.furcatumandB.hyalinumasonecladeandB.
jadranumandB.mediterraneumontheotherone.EMobservationsshowedthatthese
pairsofspeciessharesomeultrastructuralfeatures.Forinstance,B.hyalinumandB.
furcatumshareT‐shapedspinesornamentingthetwistedsetae.However,allfourspecies
sharethesamefineornamentationofthevalveandgirdlebands.Species‐specifictraits
wereencounteredaswell.Bacteriastrumjadranumpossessessmoothsetae(i.e.,without
spines)originatinginsidethevalvemargin,whiletheintercalarycellsofB.hyalinumpossess
smallY‐shapedsiliceousprojectionsonthefusedpartofthesetae.ResultsofSEM
observationsprovidedthefinemorphologicaldetailsoftheornamentationofB.hyalinum
restingspores.Thesurfaceoftheprimaryvalveiscoveredwithnumerousspines,simpleor
oftenbranchingdichotomouslyattheirendandthesecondaryvalveissmoothbearingthe
singlemarginalringofporoids.Ourresults,basedonalimitednumberofspecies,
confirmedthatinthegenusBacteriastrumthegeneralshapeofthecellsandmodeof
colonyformationaremoreinformativeonthelevelofspeciesdistinctionthanthe
ultrastructuralcharacters.


XXIIInternationalDiatomSymposium

~30~

USEOF“SPECIESSENSITIVITYDISTRIBUTION”FORHERBICIDESTOXICITY
ASSESSMENTONBENTHICDIATOMASSEMBLAGES

AgnèsBouchez,FlorianeLarras,FrédéricRimet&BernardMontuelle
INRA,UMRCARRTEL

Herbicidepresenceinlakelittoralzonesisoftencharacterizedbyahigherdiversityof
moleculesandhigherconcentrationsthaninpelagiczones.Thetolerancethresholdof
benthicdiatoms,whichrepresentagreatpartofthefixedbiomass,toherbicidesisnotwell
known.Withtheviewofassessingtheecologicalriskofherbicidesforaquatic
microorganisms,somemodelsasSpeciesSensitivityDistribution(SSD)havebeendeveloped
onphytoplanktonicspeciesofthepelagiczone.OurstudyisaimedtodetermineifSSD
modelsareadaptedtodescribethesensitivityofbenthicdiatomstoherbicides.Inthisview,
weassessedthesensitivityof11benthicdiatomsspeciesto5herbicides(diuron,
isoproturon,terbutryn,atrazinandmetolachlor).
First,weconstructedadatabaseofsensitivitythresholdsforeachherbicideandeach
diatomspeciesthought96hmonospecificbioassaysbasedongrowthinhibition.Fromdose‐
responsecurves,aneffectiveconcentrationthatinhibits50%ofgrowth(EC50)was
extrapolatedforeachdose‐responsecurve.EC50valuesshowedagreatvariabilityof
sensitivityamongdiatomspeciesforasameherbicideandbetweenallofthem.Then,for
eachherbicide,aSSDcurvewasbuiltwithEC50valuesofeachdiatomspecies(SSD‐EC50)
describingthevariationofsensitivityofdiatoms.Differentgroupsofdiatomshavebeen
definedaccordingtotheirtolerancelevel.Thisobservationwasmoreblatantfor
photosystemII(PSII)inhibitors.Forthismodeofaction,fourstrains(Nitzschiapalea,
Craticulaaccomoda,Gomphonemaparvulum,Eolimnaminima)werealwaysthemost
resistantoutofthe11testedspecies.Thistolerancecouldbeexplainedbytwolife‐history
traits:thetrophicmodeandtheecologicalguild.Indeed,N‐heterotrophandmotileguild
speciesseemedtobemoreresistanttoPSIIinhibitorsthanN‐autotrophandotherprofile
guildspecies.

XXIIInternationalDiatomSymposium

~31~

ANINTEGRATIVEANALYSISOFLIGHTRESPONSESINPHAEODACTYLUM
TRICORNUTUM

ToreBrembu1,MarianneNymark1,KristinCollierValle1,PerWinge1,MatildeSkogen
Chauton2,KasperHancke3,OlavVadstein2,GeirJohnsen1&AtleM.Bones1
1DepartmentofBiology,NorwegianUniversityofScienceandTechnology
2DepartmentofBiotechnology,NorwegianUniversityofScienceandTechnology
3NordicCenterforEarthEvolution,InstituteofBiology,UniversityofSouthernDenmark

Light‐associatedprocessesareamongthemostfundamentaltophotosyntheticalgae.
Microalgaesuchasdiatomsexperiencelarge,rapidandunpredictablefluctuationsinlight
intensityandspectralquality.Themolecularmechanismsbehindsensingandrespondingto
theseenvironmentalchangesandhowtheyareconnectedtotheobservedphysiological
responsesarestillpoorlyknown.

Wehave,throughaseriesofexperiments,investigateddifferentaspectsofthelight
responseinPhaeodactylumtricornutum.Transcriptionalprofilingusingfull‐genome
microarrays,metabolicanalyses,andvariablefluorescencetechniquewereusedto
generateanintegrativeviewofthemolecularandphysiologicalresponsesthroughseveral
timeseriesmeasurements.
1. Lowlightacclimatedculturesweretransferredtohighlightconditions
2. Dark‐grown(48h)cultureswerere‐exposedtolight
3. Adieltimeserieswasmadeoveracompleteday‐nightcycle

Resultsfromtheindividualexperimentsarepresented.Wewillalsocombinethethree
datasetsinordertorevealmorecomplexconnectionsunderlyingresponsestolight.


XXIIInternationalDiatomSymposium

~32~

DIATOMTAXONOMICCONSISTENCY:RESOURCESANDAPPROACHESATTHE
ACADEMYOFNATURALSCIENCES,PHILADELPHIA,USA

DonaldF.Charles&PatriciaPalmer
AcademyofNaturalSciencesofDrexelUniversity,PatrickCenterforEnvironmentalResearch

TheANSPPhycologySectionhasseveralresourcesavailablefordiatomresearcherstohelp
promotetaxonomicconsistency.Threeofthemostusefularethecurrentsetoftaxanames
(2011ANSP/NAWQA/EPA),thealgaeimagedatabaseandwebsite,andtheNADED
databasewithdiatomcountsandsiteinformation.Thesethreeareintegratedwitheach
otherandwithacountingprogram(Tabulator)andaprogramforcalculatingmetrics
(Phyco‐Aide).
ThePhycologySectionispartofthePatrickCenterforEnvironmentalResearch,andworks
closelywiththeDiatomHerbarium(MarinaPotapova,Curator).ThePhycologySectionhad
itsoriginsintheLimnologyDepartment,whichRuthPatrickstartedin1947.Beginning
about1994,thePhycologySectionbeganstoringdiatomcountsandrelateddatainthe
NorthAmericanDiatomEcologicalDatabase(NADED).Sectionstaffandcollaboratorshave
addeddiatomdatatoNADEDfrommanyprojectsthroughouttheUS,includingthose
nationalinscopesuchastheUSGSNationalWater‐QualityAssessmentProgram(NAWQA)
andEPA’sNationalAquaticResourceSurveys(NARS).NADEDnowcontainsmorethan
25,000diatomcounts(andmorethan16,000soft‐algaecounts)fromover10,000sitesin
theU.S.Theserecordscanbesearchedtofinddistributiondataforindividualtaxaandto
findaccessionnumbersforthecorrespondingmorethan47,000slidesarchivedintheANSP
DiatomHerbarium.
The2011ANSP/NAWQA/EPAsetoftaxanamesisanupdateofpreviousversionsandisthe
productofmuchworkbymanydiatomistsatseveralinstitutions.Itincludesrecent
synonymsfor2,000diatomtaxa(>1715described)andmorethan1100softalgae.Thisset
ofnamesanditspredecessorshavebeenusedinanalysisofalgalsamplesformanystate
andfederalprojects,includingNAWQA,NARS,andthediatomcomponentoftheNEOTOMA
paleoecologydatabase.Agencieshavesupportedthiseffortwiththegoalofprovidinga
commonandconsistentsetofnamesthatcanbeusedinprojectstheyfundsothat
resultingdatasetscanbemoreeffectivelycomparedandcombined.Filesofnamescanbe
downloadedat:http://diatom.ansp.org/nawqa/Taxalist.aspx.Eachnameisassociatedwith
auniqueNADEDID.Namesareintendedtobeconsistentwiththoseusedinthe“Diatoms
oftheUnitedStates”websiteandequivalentinformtothoseintheCaliforniaAcademy
CatalogueofDiatomNames.

TheAlgaeImageDatabaseandwebsite(http://diatom.ansp.org/algae_image/)document
manytaxainthesetsoftaxanames,particularlyundescribedandlesscommontaxa.


XXIIInternationalDiatomSymposium

~33~

EFFECTOFLIGHTONTHEACCUMULATIONOFFREEAMINOACIDSINTHE
MARINEDIATOMSKELETONEMACOSTATUMRESTINGCELLSDURING
GERMINATION

Chang‐PingChen,Qing‐YuLi,Qian‐QianZhou,LinSun,Min‐HuaZheng,Jun‐RongLiang&Ya‐
HuiGao
KeyLaboratoryforSubtropicalWetlandEcosystemResearch,MinistryofEducation,andSchoolof
LifeSciences,XiamenUniversity

Theinfluenceoflightonnitrogenuptakeandtheaccumulationoffreeaminoacidsin
Skeletonemacostatumrestingcellsduringgermination,butbeforecelldivision,were
studied.Nitrogen(N)uptakeoccurredpriortocelldivisionwhencellswereplacedinthe
light.Carbonfixationmightbetakingplacesimultaneouslyduetotheincreasingfreeamino
acidconcentration.DifferentratesofNuptakeweremeasuredafter3hdependingon
irradiancetotherejuvenatingcells,andtheresultsshowedalargeincreaseat225and300
μmolquantam‐2s‐1after12h.TherapidandincreasingNuptakeathighlightenabledS.
costatumtorebuildandreorganizeitscellcontentsquicklyandtodominatesubsequent
vegetativegrowth.Comparedtothoseinthelogarithmicphaseandstationaryphase,much
higherconcentrationsofaminoacidsglycine(Gly)andhistidine(His)weredetectedin
restingcells.TheaminoacidHisappearedtobeastoragecompoundinS.costatumresting
cells.Furthermore,alanine(Ala),proline(Pro),GlyandHisinS.costatumrestingcellscould
beassociatedwiththesurvivalofrestingcellsinunfavorableenvironments,suchasanoxic,
cold,darkandheavymetalstress,andwiththefollowingrecoveryprocess.Comparedto
glutamineat12hand36h,glutamatehadthehighest15Nlabelingenrichmentat3h,6h,24,
30hand48h,showingadielvariationofNstatusduringgermination.The15Nlabeledurea
wasdetectedat36h,comparedtotheureacycleintermediates,ornithineandcitrullineat
30h,indicatingthatureawasproducedasanNreservoirduetothehighernitrogenuptake
inthedark,andtheureacyclewasinvolvedinS.costatumrestingcellgermination.
However,inrestingcellgermination,Procouldbeproducedbyotheractivity,otherthan
theureacycle.

ThisworkwasfundedbytheNaturalScienceFoundationofChinaundercontractNo:
40906058andtheNaturalScienceFoundationofFujianProvinceofChinaundercontract
No:2011J01279




XXIIInternationalDiatomSymposium

~34~

THEIMPORTANCEOFUSINGCORRECTDESCRIPTIVETERMINOLOGYANDAN
INTRODUCTIONTODIATERM–DEVELOPINGAREVISEDGLOSSARYOF
TERMINOLOGYFORDIATOMISTS.

EileenJ.Cox
TheNaturalHistoryMuseum

Overthecourseoftimealldisciplinesdeveloptheirownspecialisedvocabularytodescribe
observationsandconcepts,thestudyofdiatomsbeingnoexception.Whereassome
descriptiveconventionshavechanged,e.g.primaryandsecondaryorsideandface,versus
girdleandvalveview,othershavebeenretainedmoreorlessunchanged,e.g.striae,raphe,
valve,frustule.Bythemid20thcentury,despitelinguisticvariations,thetermsinusefor
lightmicroscopicaldescriptionsofcleaneddiatomswerelargelyconsistentandreadily
understoodacrosslanguages.However,withthedevelopmentofelectronmicroscopyand
thediscoveryofanotherscaleofvariationindiatoms,manynewtermswereintroducedto
describeultrastructuralfeatures.ItalsobecameclearthatapparentlysimilarLMfeatures
couldhavecontrastingultrastructure.
Since,despitethedevelopmentofmoleculartechniques,morphologicalcharacterscontinue
tounderpindiatomtaxonomyandsystematics,andinferencesaboutrelationshipsare
madeonthebasisofshared(usuallyultrastructural)characters,itiscriticalthat
terminologyisappliedpreciselyandconsistently.Inaccurateterminologynotonlyproduces
confusionbutcanalsoleadtoincorrectinferencesofrelationships.
Diatermisarecentinternationalinitiativetoreviewexistingdiatomterminologyand
producearevised,highlyillustratedglossarythatcanbeusedbyalldiatomists.Itbuildson
previousterminologypublicationsbutwillalsoreviewandevaluateallsubsequently
publishedterms,inordertodeveloparationalandpracticaldescriptivevocabulary.Any
rejectionofduplicateorinappropriateterminology,aswellastheintroductionofnew
terms,willbejustifiedandexplained.


XXIIInternationalDiatomSymposium

~35~

THESPINESOFCORETHRON;TYINGUPLOOSEENDS

RichardM.Crawford
5,StMaryStreet,Cardigan,Wales

ThemagnificentspinesofthemarinediatomgenusCorethronhavebeenacknowledgedas
uniqueforsometimeyetthecomplexrelationshipofthethreedifferenttypesofspinein
eachcellwhenheldbeneaththecylinderofthecingulumhasremaineddifficulttoestablish.
Now,newinformationhasemergedfromolddatatorevealasituationevenmorecomplex
thanwasthoughtbutwhichallowsustounderstandhowthediatomtiesupitslooseends.

XXIIInternationalDiatomSymposium

~36~

HOLOCENEVARIABILITYOFTHENORTHAMERICANMONSOON:DIATOM‐
BASEDEVIDENCEFROMLAKESEDIMENTSINWESTERNMEXICO.

SarahDavies1,SarahMetcalfe2,BenAston1,MelanieLeng3,4&MatthewJones2
1InstituteofGeographyandEarthSciences,AberystwythUniversity
2SchoolofGeography,UniversityofNottingham
3NERCIsotopeGeosciencesLaboratory,BritishGeologicalSurvey
4DepartmentofGeology,UniversityofLeicester,UniversityRoad,Leicester,LE17RH,UK.

Wepresentamulti‐proxysedimentrecordfromLagunadeJuanacatlán,Jalisco(20°37'N,
104°44'W),inthewesternfringesoftheTrans‐MexicanVolcanicBelt.Thelakeliesinthe
coreoftheNorthAmericanMonsoonregion,withmorethan80%ofprecipitationoccurring
betweenMayandOctober.WhilstthePacificOceanisthedominantinfluence,moisture
originatingfromtheGulfofMexico/Atlanticisalsoimportant.Thisuniquesedimentary
archiveprovidesanopportunitytoinvestigatelongtermchangesinmonsoonintensity
duringtheHolocene.High‐resolutionX‐rayfluorescenc(XRF)analysis,magnetic
susceptibilityandorganicgeochemistryarecombinedwithdiatomspeciesdataandoxygen
isotopeanalysisofdiatomsilicatoprovideamulti‐proxyreconstructionofclimate
variability.
LagunadeJuanacatlánliesatc.2000ma.s.l.andhasamaximumdepthofc.28m.Periodic
monitoringhasrevealedthatthelakeisconsistentlythermallyandchemicallystratified.Its
watersareofcalcium‐magnesium‐bicarbonatecomposition,withapHofc.8.5and
electricalconductivityof105µScm‐1.Lyinginaremote,mountainousarea,thelakehas
experiencedminimalhumanimpact,meaningthattheclimaticsignalshouldnotbe
obscuredbyanthropogenicdisturbance.
A7.8mcompositesequenceoffinelylaminatedsedimentsprovidesanannuallyresolved
recordspanningthelast6000calyrsBP.Laminationsarecomposedofalternating
minerogenicandorganic‐richdiatomaceouslayers.Downcorediatomassemblagesare
dominatedbyDiscostellastelligera,Aulacoseiragranulata(+var.angustissima),punctuated
bybriefperiodsofdominancebyNitzschiapaleaat1000calyrsBPand3200calyrsBP,
reflectingincreasednutrientconcentrations.Synedraspp.becomemoreimportantafter
1000calyrsBP,beingreplacedbyFragilariacrotonensisinthemostrecentsediments.
Thesetaxaarealsofoundinsignificantnumbersbetween5000and6000calyrsBP.Diatom
specieschangesarebestexplainedintermsoffluctuationsinnutrientandlightavailability
ratherthanioniccompositionorconcentration.Diatom