coccolithophores optical properties, ecology, and ... · impact of climate change on phytoplankton...

Griet NeukermansMarieCuriePostdoctoralFellow

Laboratoire Océanographique deVillefranche-sur-Mer

COCCOLITHOPHORES

Optical properties, ecology, and biogeochemistry

Griet NeukermansPhDinopticaloceanographyMSc.Mathematics(VUB-Belgium)MSc.Oceans&Lakes(VUB-Belgium)

RemotesensingandlightscatteringpropertiesofsuspendedparticlesinEuropeancoastalwaters(PhD,ULCO-France,advisors:H.Loisel andK.Ruddick)

ImpactofclimatechangeonphytoplanktonbloomsontheArcticOcean’sinflowshelves(BantingPostdoctoralFellow,ULaval-Canada,advisor:M.Babin)Remotesensingofoceancolour andphysicalenvironment

+Modelingthelightscatteringpropertiesofcoccolithophores (withG.Fournier)

Polewardexpansionofcoccolithophore bloomsandtheirroleinsinkingcarbonintheSubarcticOcean(MarieCuriePostdoctoralFellow,LOV-France,advisor:H.Claustre +co-advisors:G.Beaugrand andU.Riebesell)Opticalremotesensing+Ecologicalnichemodeling+opticalmodeling+Biogeochemical-Argofloats

Opticaldetectionofparticleconcentration,size,andcompositionintheArcticOcean(PostdocSIOUCSD-USA,advisors:D.Stramski andR.Reynolds)

Coreexpertise:developmentandapplicationofremoteandinsituopticalsensingofmarineparticles

2008

2012

2014

2017

now

PhD

Post

doc1

Postdo

c2Po

stdo

c3

When not at work… I ride my bike!

This course covers• Coccolithophore biologyandecology

– Diversity,distribution,andbiomass• Remotesensingofcoccolithophores andtheircalcitemass(PIC)

– Bloomobservationsandclassification– QuantifyingPICintheocean– CaveatsofremotelysensedPIC

• Opticalpropertiesofcoccolithophores– Scattering,backscattering,andabsorption– Reflectance– Birefrigence

• Someapplicationsofopticaloceanographyincoccolithophoreresearch– Ecology(environmentalcontrolofcoccolithophore blooms,

phenology,oceanalbedo)– Climatechangeimpacts– Biogeochemistry(influenceonpCO2, calciteballasteffect)

Mon

teiro

eta

l.(201

6–Sci.Ad

v.)

5µm

What are coccolithophores?• Calcifyingphytoplankton• Haptophyta;Prymnesiophyceae• ProduceCaCO3 scales(coccoliths)• About200species• Occurthroughouttheworldocean• 5 µm≤D≤40µm• Consideredasasinglefunctional

groupwithinthephytoplankton(>biogeochemistry)

• Compriseabout10%ofglobalphytoplanktonbiomass

• MajorCaCO3 producersintheopenocean(besidesforams andpteropods)

5µm

Coccolith production

Coccolithus pelagicus

Videomicroscopy Courtesy:AlisonTaylor Tayloretal.2007Eur.J.Phycol.

Producesabout1coccolithevery1.5-2h

D=10-40µm

Coccolith functionMon

teiro

etal.(2016–Sci.Ad

v.)

Whydococcolithophores calcify?

Monteiroetal. (2016 – Sci.Adv.)

5µm

• Temperatureandlightarekeydriversoflatitudinaldiversitypatterns

• Diversityishighestinthelowerlatitudes• Diversityislowestathigherlatitudes,whereassemblagesareoften

dominatedbythebloom-formingspeciesE.huxleyi (Ehux)

O’Brie

netal.,201

6–Progr.Oceanogr.

annualmeancoccolithophore diversity

Coccolithophore distribution and diversityCoccolithophore speciesexhibitdistinctvertical and latitudinalzonation.

Coccolithophore distribution and diversity

Monteiroetal. (2016 – Sci.Adv.)

5µm

Coccolithophore speciesexhibitdistinctverticalandlatitudinalzonation

Balchetal.,2017– Ann.Rev.Mar.Sci.

Thepresenceofdeep-dwellingspecieswellbelowthephoticzonehasbeentakenasevidence

Ehux

Throughouttheeuphoticandaphoticzone,accordingtotheirecologicalpreferences.

Mixotrophy?

Ehux isdistinctfrommanyotherspeciesinthatitiscommoninallphoticzones

Coccolithophore biomass distribution

• Mostcomprehensiveinsitudatasetofcoccolithophore biomassfrommicroscopyorflowcytometry(1929-2008)

• About11000observationsoftotalcoccolithophore abundanceandbiomass(O’Brienetal.,2013– ESSD)

0-5mdepth

ThisisOrganicbiomassorPOC

(O’Brie

netal.,201

3–ESSD

)

Coccolithophore PIC in the ocean

• OCRSprovides daily globalobservations of PIC• …butthealgorithm haslimitations…

VIIRSoceancolour satelliteannualcomposite(2017)

GreatCalciteBelt(Balchetal.,2011,JGR)

BarneyBalchBigelow(USA)

Remote sensing of coccolithophores and their calcite mass (PIC): a chronological overview of approaches

1. Holligan etal.(1983):bloomobservationsfromCZCSRrs at550nm2. Balchetal.(1991):bloomobservationsfromAVHRR+insituIOPs3. BrownandYoder(1994):coccolithophore bloomclassifierforCZCS4. Gordonetal.(2001):quantificationofPIC(high),NASA’sstandardalgorithm5. Balchetal.(2005):quantificationofPIC(low-med),NASA’sstandardalgorithm6. Shutler etal.(2010):coccolithophore bloomextentinshelfseasandcoastal

zones– probably theonly case2algorithm7. Sadeghi etal.(2012): SCIAMACHY,based onabsorption8. Mooreetal.(2012):bloomclassifierbasedonfuzzylogicforallOCsensors9. Mitcheletal.(2017):quantificationofPICbasedonreflectance-difference

approach

First observations of coccolithophore blooms

• From ships inNorwegian fjords:« unusual milky turquoisecolour caused byenourmous concentrationsofthecalcareousflagellate Coccolithus huxleyi upto115x106 cells/Linsurfacewater»(Birkenes andBraarud 1952;Berge,1962).

• Firstbloomsdiscovered from space:– Landsat in1977(LeFevre etal.,1983)– CZCSin1982+ship (Holligan etal.1983)

See http://www.noc.soton.ac.uk/soes/staff/tt/eh/v_0.htm fordetails

LANDSATMSS4(0.5-0.6µm)2July1977

E.huxleyi

MODISnatural-colorimageAugust2011

©NASA

https://oceancolor.gsfc.nasa.gov/

Landsat8/OLI(OperationalLandImager)truecolour compositeimagefromJune18,2018.

Holliganetal.,198

3–NatureLett.

CZCS550nmJune1979 CZCS550nmMay1981 CZCS550nmMay1982

CZCSreflectanceinbloomwaters

Coastalhigh[sediments]

CZCSre

flectance443

nm

Ship- andsatellite-borneobservationsofEhux bloomsataEuropeancontinentalshelfedge.

First OCRS observations of blooms - CZCS

SignificantpositivecorrelationwasfoundbetweenreflectancefromeachoftheCZCSchannels(443,520,and550nm)andthesurfaceabundanceofcoccolithophores.

CoastalLow [sediments]

Bloom observations from AVHRR (1)Ba

lchetal.,L&O(1991)

Balch etal.(1991)andAckleson andHolligan (1989)suggested that thehighbackscattering wascaused principally bythepresence ofdetached coccoliths,rather than bycoated cells.

Ship- andsatellite-borneobservationsofEhux bloomsintheGulfofMaine

Bloomareaabout50000km2

AVHRRChangingcoccolith:cellratio

Insitubackscatte

ringdu

etococclith

s

“Freecoccoliths dothebulkofthelightscatteringinEhux bloomsbutreflectanceismorelikelyafunctionofcoccoliths and(coated)cells.”[Balch etal.(1991)]

Firststudyconnectinginsitubiogeochemicalandopticalmeasurementswithsatellitedata(AVHRR)duringanEhux bloomSouthofIcelandin1991

Holliganetal.,199

3–GB

C

Levelsofdimethylsulphide (DMS)insurfacewaterswerehighcomparedtoaverageoceanvalues,withthegreatestconcentrationsinlocalizedareasCharacterized byhighratesofPhotosynthesis,calcification,andgrazing bymicrozooplankton.

Bloomarea: 0.5millionkm2

(sizeofSpain)

Bloom observations from AVHRR (2)

Coccolithproductionhadasignificantimpactonthestateofthein-waterpCO2

5µm

Coccolithophore blooms

Young,J.R.,Bown P.R.,LeesJ.A.(2017)Nannotax3website.InternationalNannoplankton Association.www.mikrotax.org/Nannotax3

Gephyrocapsa oceanicaEmiliania huxleyiCoccospheres,D6to10µm;coccoliths,3.5to6µmlong.

Coccospheres,D5to10µm;coccoliths,2to5 µmlong.

Twoknownbloomformingspecies(“bloom”means>106 cells/L)

Predominantlylow-latitudewarm-watereutrophicspecies.MorewidespreadinthePacificthanintheAtlanticOcean.

Ubiquitous species,dominantbloom-formerintemperateandsubpolarwaters.

Ehux isthoughttobeunique inoverproducingcoccoliths andthensheddingtheexcessonesintothewater(Paasche 2002)->hardlyanyoftheopen-oceanbrightwatersareattributabletospeciesotherthanEhux.Butsee(BlackburnandCresswell,1993)forG.oceanica bloominAUS.

Emiliania huxleyi (Ehux)

http://www.noc.soton.ac.uk/soes/staff/tt/eh/

CreatedbyTobyTyrrellatSouthamptonUniversity

Coccolithophore bloom classification - CZCSBrow

nandYode

r,J.Geophys.Res.(199

4)

SupervisedmultispectralclassificationschemefromweeklyCZCSdata(1978-1986)fromnLwmagnitudeandband-ratios.

MisclassificationsofbloomsduetosimilaritywithWhitingsSediments

Coccolithophorid bloomsannualcoverage:1.4x106km2

CZCS(1978-1986)climatologyofcoccolithophore blooms

AmodifiedversionofthisclassifierisusedasNASA’sL2coccolithophoreflag.

Blooms

BrownandYoder (1994)

oBluewater

Whiting Sediments

Coccolithophore bloom classificationMooreetal.(2012),RSE

Generalizedbloomclassifierforalloceancolour sensors(SeaWiFS,MODIS,MERIS)basedonfuzzylogic.Detectionlevels:1500-1800cells/mLand43000-78000liths/mL

SeaWiFS spectraincoccoblooms+8clustermeans

clustermeansofotherOWTs(fromclearbluetoturbidcoastal)

+8cocco clustermeans

Globalannualcoccolithophore bloomcoverageofabout2.75x106km2:2x106km2 inSouthernHemisphereand0.75x106km2 inNorthernHemisphere.

Typicallypeakat490nmPercentageofcoccolithophore bloomsdetectedfromweeklySeaWiFSdata(1997-2010)

PIC in blooms from SeaWiFSGo

rdon

eta

l.(200

1)

3-bandalgorithm retrieving rw(546nm)fromSeaWiFS reflectance inRed andNIRbands(670,765,865nm)

SuitableforhighconcentrationsofCaCO3,whenB-Gbandsoftensaturate(notaccurateforPICconcentrations<3mmol m-3)

Assumptions:• rw(765,865nm)=0• rw(l)=bb(l)/(6(aw(l)+bb(l)))withl=670nm

Gordonetal.(2001)

Balchetal.(1991)

Heartofthealgorithm:bbpic(546nm)=1.6x[PICinmol m-3]-0.0036bbpic(l)=bbpic (546)x(546/l)1.35[BasedoninsitumeasurementsbyBalchetal.(1991)]

maximumRMSerrorofthealgorithmis+/- 15μg/L(or1.2mmol m-3)=about5-10%ofPICindensebloom(Balch,2004)

PIC from MODISBa

lchetal.(200

5)

PICisretrievedfromaLUTbasedonsemi-analyticalOCRSmodelofGordonetal.(1988)

Look-upTable(LUT)

Retrievaluncertainty:duetonaturalvariabilityinphytoplankton-detritusbb correspondsto25x 106 coccoliths/L=5µgPIC/L=0.41mmol PIC/ m3

1µgPIC/L=0.083mmol PIC/ m3

1mmol PIC/m3=12µgPIC/L

Validatedwithinsitudataofbbpic,PIC,Chla,andLw mainlyinMainewaters(Ehuxdominated)

Majorlimitations:• dependencyonthereflectancemodel(assumedconstantphyto-detritusbb)• absoluteradiance->sensitivitytoatmosphericcorrectionerrors• Estimateof“excessbackscatter”->particlesotherthanPICmayalsocauseexcess

backscatter

Balchetal.(2005)

0.83

1.66

2.5

mmol PIC/m3

Heartofthealgorithm(sameasGordonalgo):bbpic(546nm)=1.6x[PICinmol m-3]-0.0036bbpic(l)=bbpic (546)x(546/l)1.35

NASA’s standard PIC algorithm

MainlyvalidatedinMaineandSouthernOceanwaters.

ahybrid of2-bandapproachofBalchetal. (2005)andthe3-bandapproachofGordonetal.(2001)

The2-bandapproachofBalchetal.(2005)isapplied,unlessreflectancevaluesfalloutsidetheboundsoftheLUT(<40µgPIC/Lor3mmol PIC/m3);thenthe3-bandalgorithmofGordonetal.

(2001)isused.

Thealgorithmisapplicabletoallcurrentoceancolorsensors.

“BalchandGordon”

https://oceancolor.gsfc.nasa.gov/cgi/l3

PIC algorithm caveatsFalsepositivesforhighPIC(highly reflective waters)produced by:

• Whitings =patchesofsuspendedfine-grainedcalciumcarbonate

https://earthobservatory.nasa.gov/ (Dierssen etal.,2009– Biogeosciences)

BahamasBanks

• Highconcentrationsofemptydiatomfrustules(e.g.onshallowshelves,Broerse etal.,2003)orsuspendedsediments

• Inpolarwaters:Floatingsea-ice• Bubbles• Phaeocystis foam

• Glacialrockflourinsomehigh-altitudelakes

(e.g.,Dierssen etal.,2002).

(SeeBalch,2018,Ann.Rev.Mar.Sci.orTyrrellandM

erico,2004)

Alternative PIC algorithmMitchelletal.(2017)

PotentialtoreplacetheBalchetal.(2005)algorithmcurrentlybeinginvestigated

Reflectancedifferenceapproach,inspiredbyHuetal.(2012)forChla

MoreresistanttoatmosphericcorrectionerrorsandresidualerrorsinsunglintcorrectionsthantheBalchetal.(2005)algorithm.

Light absorption properties of coccoliths

Measurementsofap(l)(filter-padtechnique)inEhux bloomintheGulfofMaine.

Balchetal.,L&O(1991)

Lightabsorptionbycoccolithsisnegligible

ConsistentwiththeabsorptionpropertiesofcalciteforwhichtheabsorptionisnegligibleeveninthefarUV(Palik,1998- HandbookofOpticalConstantsofSolids).

Light absorption by Ehux cells

MeasurementsfromEhux cultures

TypicalChla contentforEhux =0.24pg Chla/cell(Ahn etal.,1992– DeepSeaRes.),upto0.4pg Chla /cell(Danielsetal.,2014– Biogeosciences)

->0.24pg - 0.40pg Chla x106 cells/Linabloom=0.24-0.40µg/Linabloom.

Chromatogram(HPLCmethod)

Moreland

Bricaud,DeepSeaRes.(1981)

Zapataeta

l.,M

EPS(2004)

Incell

Pigmentsinsolution

MeasuredinEhux culture

Light scattering properties

Theyaremadeofcalcitewithrefractiveindex=1.20relativetowater(otherrefractiveindicesforreference:1.05forPOC,1.07forBSi),whichmakesthemhighlyefficientlightscatterers

Morel(1

991)

Light scattering properties of calcite particles in the ocean

Calcite-specificscatteringcoefficientissize-dependentaccordingtoanomalousdiffractiontheoryfornon-absorbingspheres(VandeHulst,1981).

Balchetal.,L&O(1996)

Foraminifera(0.05-1mm)(amoeboidprotozoans)

Pteropods (1-3mm)”seasnails”

Coccolithophores &liths

Negligiblecontributionfromlargercalciteparticles(foramsandpteropods)tobb andthustoRrs

basisofNASA’s standardPICalgorithm:bbpic/PIC=constant

Balchetal.(1991)Insitu:inbloom

Light backscattering vs. PIC

Changingcoccolith:cellratio?

Neukermans andFournier(2018)– F.Mar.Sci.

Opticalmodeling studies (ADA,DDA)showthatbbpic/PICdoes notdepend much onwhethercoccoliths areattached toarefreed from thecoccoshpere(see also Gordonetal.,2009,Appl.Opt.)

Light backscattering properties of EhuxStrongly depend oncoccolith morphology (andsize,indirectly)

SEMofE.huxleyi (J.Young)

ModelofE.huxleyi coccolith

(seeGordon,2006,Appl.O

pt.;Gordonetal.,2009,Appl.Opt.;Zhaietal.,2013,O

pt.Expr.)(FournierandNeukermans,2017,Opt.Expr.;Neukermans andFournier,2018,F.Mar.Sci.)

Backscatterin

gefficiencyfactor,Q

bb

Light backscattering properties of Ehux

Platedcells

Nakedcells

Freecoccoliths

bbpic(l)=bbpic (546)x(546/l)z

z=1.2

z=1.0

z=1.4

Inculture

Note:highmeasurementuncertainty

Vosseta

l.,L&O(1998)

z=0.77

z=0.94ModelofNeukermans andFournier(2018)–F.Mar.Sci.

Ehux has various morphotypes

2µm

2µm

2µm

Poultonetal.,201

1(M

EPS)

DifferentEhuxmorphotypes areexpected(intheory)tohavedifferentmagnitudeandspectralshapesforbackscattering

Morphotype A

Morphotype B/C

Hagino etal.,2011(J.Phycol)

Morphotype R Morphotype OImages:Young,J.R.,Bown P.R.,LeesJ.A.(2017)Nannotax3website.InternationalNannoplankton Association.www.mikrotax.org/Nannotax3

Ehux bloomintheBarentsSea,17August2011.

MODIS

TrueColour CompositefromMODISAqua

The milky-turquoise hue of Ehux bloom waters?

MODISPIC(mol m-3)

The milky-turquoise hue of Ehux bloom waters?

Neukermans andFournier,F.Mar.Sci.(2018)

Allliths attached Allliths freedX36togetcoccolithconcentr.

Allliths freed,changing semi-majoraxisAllliths freed,changing CDOMNote:Rrs normalized at550nm

Calcite is strongly birefrigentIncomingdifferenteffectiveindexofrefractionthanlightintheperpendicularpolarizationdifferentangle

Birefringencecanbedetectedchangesinthepolarizationoflightpassingthroughthematerial(e.g.,polarizedlightmicroscopy)

Guay

andBishop

,Deep

SeaRes.

(2002)

https://en

.wikiped

ia.org/w

iki/B

irefringence

ProvidedthebasisforaninsitumarinePICsensor(theCarbonFluxExplorer– Bishopetal.,2016,Biogeosciences)

Spectrophotometertechnique=transmittance+linearpolarizers

“Birefringencereferstotheabilityofamineralcrystaltosplitanincidentbeamoflinearlypolarizedlightintotwobeamsofunequalvelocities(correspondingtotwodifferentrefractiveindicesofthecrystal),whichsubsequentlyrecombinetoformabeamoflightthatisnolongerlinearlypolarized.”

Birefringencecanbedetectedbymeasuringthechangesinthepolarizationoflightpassingthroughthematerial(e.g.,polarizedlightmicroscopy)

Carbon Flux ExplorerIncomingdifferenteffectiveindexofrefractionthanlightintheperpendicularpolarizationdifferentangle

Birefringencecanbedetectedchangesinthepolarizationoflightpassingthroughthematerial(e.g.,polarizedlightmicroscopy)

Bishop

eta

l.,201

6,Biogeo

sciences

Not(yet)fullyautonomous(duetoimageprocessing)

Resolutiontoocoarsetoresolvecoccolithophores…

marine-snowaggregateofabout1cm

Attenuance arized Counts Imageresolutionis13μm.

600 μm

Brightspheres=200μm sizedforaminiferashells

Designedtoperformsustainedhigh-frequencyobservationsofPOCandPICsedimentationwithintheocean’stwilightzone

Environmental control of coccolithophore blooms

Large-scaleseasonalbloomsofEhux detectedbyOCsatellitesaregenerallyassociatedwith:

• Temperateandsubpolarwaters• AfteradiatomSpringbloom(succession)• Relativelyhighcriticalirradiances• Stablewatercolumn• Decliningnutrients

Signoriniand

McClain(2009–G

RL)

Balch(2004),adapted

from

Margalef(1978)

[seeIglesias-Rodrigezetal.,2002;TyrrellandM

ercio,2004;Balch2004;SignoriniandM

cClain,2009]

Succession or coexistence of phytoplankton populations Ho

pkinse

tal.(2015–G

BC)

Areasattributesbeexpectedtoberegionswheresignificantshiftsinenvironmentalconditionsleadtophytoplankton

Margalef’s (1978) BarberandHiscock(2006)Succession:shelfregions,upwellingareas,andtheHLNAinsupportofMargalef’s suggestionthatenvironmentalchangespromotetheproliferationofonetaxaattheexpenseofanother.

Coexistence:acrossmuchoftheopenoceaninsupportofBarberandHiscock(2006)’ssuggestionofcoexistencethroughdifferencesinbiomassaccumulationrates,whileactualcompetitionbetweenthetwopopulationsiskeptincheckthroughvariabilityinnutrientuptakeratesandshiftsinthedominantgrazersandtheoverallfoodwebstructure.

Coccolithophore phenologySeasonalvariabilityinPICisidentifiedacrossmuchoftheglobalocean

Hopkinse

tal.(2015–G

BC)

peak PIC concentration

bloom start month bloom peak month

bloom duration

BasedonMODIS8-dayPICclimatology(2003-2012)

Ehux blooms: brighter surface ocean, darker deeper down

Ehux bloomsincreasesoceanalbedo

Contributiontoglobalannuallyaveragedplanetaryalbedoisabout0.13%

But,stronglocaleffects:

(Hovland etal.,2013- J.Mar.Sys.)

Ehux bloomsshoaltheeuphoticzone,diminishingthelightavailablefordeeperalgalspecies,limitingphotosynthesisatdepthby20–40%wherenutrientlevelsareotherwisesufficient

(Tyrrelletal.,1999- JGR)

=0.025mol Cm-3

Poleward expansion of EhuxProposedbyWinteretal.(2014– J.PlanktonRes.),basedonOCRS(CZCSandSeaWiFS)andinsitudata.

fromCZCS(1978-1986)

fromSeaWiFS (1997-2007)

Clim

atologyofclassified

coccolitho

phorebloo

ms

BarentsSea

Coccolithophore datawithin30°-70°S/130°-170°E

Bloomsizeandintensityincreasedinthe1990s.Why?

Poleward expansion of E. huxleyi blooms:On an Arctic inflow shelf (Barents Sea)

Warm(T>3°C)andsalineAW

WarmandfreshCoastalwaters

Cold(T<0°C)andfreshArW

Neukermans etal.(Glob.ChangeBiol.,2018)

Approach:

Combinelong-term(1980s-2016)remotesensingdataofEhux

bloomswithremotesensingdataofthe

physicalenvironment(seasurfacetemperatureandseaice)

PolewardexpansionofEmiliania

huxleyi bloomsintheBarents

SeaandAtlantic

waters

Neu

kerm

anse

tal.(Glob.Ch.Biol.,201

8)Summer max

Bloom threshold

390km(1989-2016)

n.s.

501km(1989-2016)56km/yr

(2010-2016)

Rangeshift

Smythetal.(2004– Geophys.Res.Lett.)

Neu

kerm

anse


8)

SeaWiFSAVHRR

MODIS

Globalmeanratefor:marinespecies=7.2km/yr,phytoplankton=35.8km/yr,zooplankton=14.2km/yr

Poloczanskaetal.(2013– Nat.Clim.Ch.)

Poleward expansion of E. huxleyi blooms

Atlanticwatertemperature(Kolahydgrographic section)

Neu

kerm

anse


8)

Summermean

AnnualmeanE.huxleyi bloomdetected

Opticalremotesensing

PolewardexpansionintheBarentsSeaisdrivenbyincreasedintrusionandwarmingofAtlanticwaters

Poleward expansion of E. huxleyi blooms

1980 1985 1990 1995 2000 2005 2010

AtlanticWatervolumetripledèAtlantification (Arthun etal.,2012– J.Clim.)

(Ozieletal.,2016–OceanSci.)

Role of Coccolithophores in Ocean carbon cycle

Therelativestrengthsofthesetwopumps(rainratio)largelydeterminethebiologicallymediatedoceanatmosphereCO2 exchange.

Thebiologicalcarbonpumps

Organiccarbonpump:PhotosyntheticproductionoforganicmatterinthesurfacelayeranditssubsequenttransporttodepthgeneratesaCO2sinkintheocean.

Carbonatecounterpump:CaCO3productionanditstransporttodepth,releasesCO2 inthesurfacelayer.

Rost andRiebesell (2004)

Using10yearsofSeaWiFS dataofclassifiedEhux bloomsintheNorthAtlanticandclimatologies ofpCO2 inair,seawater,salinity,solubilityandgastransfervelocity:

ItwasestimatedthatEhux bloomscanreducetheannualnetsinkofatmosphericCO2 by3–28%.

Shutleretal.(2013– Biogeosciences)



Ballasthypothesis: E.huxleyi calcitematerialballastsorganiccarbonbyincreasingsinkingspeedandprotectingorganiccarbonfromremineralisation (Françoisetal.,2002)

widelydebatedandpoorlyunderstood Mesocosm experiment

Hamperedbypaucityandlimitedresolutionoftraditionalparticlefluxmeasurements(fromsedimenttrapsandradiochemicaltracers)

Canweexaminecalciteballastingusingbio-opticalmeasurementsonBiogeochemical-Argofloats?

1. Canweidentifycoccolithophore bloomsfromfloats?2. Canwequantifyassociatedsinkingparticle(carbon)fluxes?

Riebeselletal.(2016– Nat.Geosci.)

Currentfloatposition

Profilesonfloattrajectory

Iceland

Observing E. huxleyi blooms with BGC-Argo floats

Neukermans etal.(inprep.)


Lightb

ackscatte

ring,b

bp(m

-1)

Beam

atte

nuation,cp/100

(m-1)

2008 2009

2008 2009

Refra

ctiveindexofparticles

Twardo

wskieta

l.(200

1)

Neukermans etal.(inprep.)

PositionofBGC-Argofloats,February2018

haveacp sensorandsampledacoccolithophore bloom

ByM.Cornec


PositionofBGC-Argofloats,February2018

haveacp sensorandsampledacoccolithophore bloom

ByM.CornecByL.Terrats


Thankyou!

coccolithophores optical properties, ecology, and ... · impact of climate change on phytoplankton...

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