世界銀行-了解漁業(yè)和水產(chǎn)養(yǎng)殖在碳封存中的作用（英）

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UnderstandingtheRoleofFisheriesandAquaculturein

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WhitePaper

UnderstandingtheRoleofFisheriesandAquacultureinCarbonSequestration

1

UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

Contents

EXECUTIVESUMMARY 3

GLOSSARY 4

1.METHODS&SCOPE 5

2.INTRODUCTIONTOTHEBIOLOGIALPUMP 6

3.MODELINGTHEFISHCARBONPUMP 10

3.1Metabolic'production'processes 10

3.3definitionofkeystocksandflows 11

3.4Metabolic'production' 12

3.4.1Livingbiomass 16

3.4.2CarcassProduction 17

3.5biocheMicaltransforMations 18

3.6phyicaltransports 21

3.6.1.Fishactiveverticaltransport 21

3.6.2Watermassflows 21

3.7MobiledeMersalfishinggears-carbonsediMentinteractions 23

3.8Marinebenthicproducercarbonsequestraton 26

4.ICESWORKSHOPONASSESSINGTHEIMPACTOFFISHINGONOCEANICCARBON 29

4.1carbonpuMp 29

4.2fishingfleeteMissions 32

4.3fishingiMpacts 32

4.4furtherwork 32

5.RELEVANTPOLICYINITIATIVES 33

5.1unitedkingdoM 33

5.2europenaunion 33

5.3internationalcouncilfortheexplorationoftheseas 33

6.CONCLUSIONS 34

7.RECOMMENDATIONSANDNEXTSTEPS 36

7.1digitalresarchplatforM 36

7 1.1Quantifyfishandfisheriescarbonflows..........................................................................................................36

7.1.2Macroalgaldynamics 37

7.1.3Interactingwiththeenvironment 37

7.1.4Developmenttimelineandwiderimpact 37

7.2standardizingthedialogue 37

REFERENCES 38

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

Figures

Figure1:Mainprocessesregulatingthemarinecarboncycling(reproducedfromLutzandMartin,2014) 6

Figure2:Mainpathwaysandprocessesofthebiologicalpumpwithaspecificfocusonfish 8

Figure3:Modelsneededtoquantifythebiologicalpumpcarbonsequestrationofmarineecosystems 9

Figure4:Directandindirectimpactsoffishingoncarbonsinkdeadzones 11

Figure5-Fishandfisheriescarbonfluxscheme 12

Figure6-ConceptualviewoftheoceanicCaCO3cycle 15

Figure7-Simplifiedschemeoftheglobalcarboncycle.N 18

Figure8:Top-Mainfluxesandcarbonbudget;knowledgegapsandresearchpriorities 24

Figure9:Conceptualdiagramofthepathwaysforexportandsequestrationofmacroalgalcarbon 26

Figure10:Macroalgalcarbonsequestrationscheme 27

Tables

Table1:Sequestrationandsequestrationtimeofthebiologicalpumppathways 7

Table2:Productiontable 13

Table3:Remineralizationrates 19

Table4:Sinkingratesreferencevaluesforfishandzooplanktonfecalpelletsandcarcasses 19

Table5:Biochemicaltable 22

Table6:Physicaltransporttable 22

Table7:Keyresuspensionvariables 23

Table8:Linkbetweenseabedsedimentorganiccarbonandmobiledemersalfishing 25

Table9-Marinemacroalgaereferencevalues.(AdaptedfromKrause-JensenandDuarte,2016) 27

Table10:Summaryofkeyvariablesofbiologicalcarbonpumpmodelling,andwhytheymatter 30

Table11:Riskassessmentandconfidenceassessmentofenvironmentalfactorsgoverningseabedcarbon

remineralizationandstorage 31

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

EXECUTIVESUMMARY

Theoceanplaysacrucialroleinregulatingtheclimatebyabsorbingexcessiveheatandcarbondioxideemissions.Inadditiontosolubilityandthephysicalpump,thebiologicalpumpisincreasinglyacknowledgedasavitalcomponentofoceanecosystemservices.Marinelifecontributestotheabsorptionofatmosphericcarbonandsequestersitin

themarineenvironmentthroughvariousprocesses,withsequestrationoccurringfortimeperiodsrangingfromdailyprocessestothousandsofyears.

Inthiscontext,thereisagrowinginterestamongboththescientificcommunityandawidenetworkofstakeholderstoenhanceunderstandingandmodelingcapabilitiesconcerningfishandfisheries’carbonsequestrationprocesses.Overthepastfewdecades,significantprogresshasbeenmadeincomprehendingandcharacterizingtheseprocessesfor

theopenocean,resultinginabroadandexpandingliteraturewithsubstantialinformationonmanykeyparameters.Nonetheless,therearestillsignificantknowledgegaps,especiallyforcoastalandshelfareas,andthescientific

communityisactivelystrivingtoestablishacomprehensiveconsensusonessentialelementsrequiredforaccuratelyevaluatingtheeffectsoffishingactivitiesandpoliciesonmarinecarbonsequestration.

ThisASAsoughttoaddressthedevelopmentchallengeofcomprehensivelyquantifyingthecarbonsequestration

attributabletoimprovedfisheriesmanagementandaquaculture.ItfocusedondeliveringawhitepaperthatdescribesexistingandpotentialGHGaccountingmethodstoinformclimate-mitigationco-benefitsassessmentsofimprovedfisheriesmanagementandaquacultureproductioninvestmentsforamorecomprehensiveestimate.Theoutcomesofthisworkculminatedinawhitepaperwhichreliesonadetailedliteratureandstakeholderconsultationstoassessthepossibilityofenhancingexistingmodelstoovercometheidentifiedknowledgelimitationsinordertofurtherourknowledgeonhowtobettercapture/estimateclimate-mitigationco-benefitsfromimprovedfisheriesmanagementandseaweedproduction.

Thiswhitepaperprovidesthecurrentstateofscientificunderstandingofthefield,andsuggestsnextstepsforwardintermsofhowmodelingcancontributetofillingthisgap.Thereportisstructuredtosupportthefuturedevelopmentorenhancementofmodels,featuringamapofthekeystocksandflows,ananalysisofhowfishtransformand‘produce’carbon,anexplorationofthecarbonbiochemicaltransformationsinthemarineenvironment,andanexamination

ofphysicaltransportwithinthemarineecosystem.Additionally,itincludesdedicatedsectionsontheimplications

ofsedimentinteractionswithmobiledemersalfishinggearsforcarbonsequestration,thesignificanceofmarine

macroalgae-kelpecosystemsinthebiologicalcarbonpump,andnoteworthypolicyinitiativesrelatedtomarinecarbonsequestration.

Theresearchconductedhereidentifiedgeneralgaps,suchastheneedtobettercharacterizehowdifferentfish

contributetoandconsumethevariouscarbonflowsidentifiedinthemarinerealm,ortheneedtobettercharacterizetheinterrelationbetweentrawlingactivitiesandsedimentaryecosystems.Specificdifficultieshavebeenidentified

arisingfromthefactthatmostfishingactivitiestakeplaceonthemarineshelf,wherekeyphysicochemicaland

biologicalprocessesareoftenmorecomplexthanintheopenoceanwherecarbonflowsarebetterunderstood,leadingtoahigherlevelofcomplexityinevaluatingcarbonsequestrationtimesincoastalareas.

Thiswhitepaperconcludeswithasummaryhowexistingmodelscouldbeenhancedtoovercomesomeoftheidentifiedknowledgelimitations.Toaccomplishthis,thedevelopmentofcoupledfood-webmodelswithcarbonsequestration

modelsisproposed,aimingtoattainamorerealisticunderstandingoftheimplicationsoffishingactivitiesforcarbonsequestration.Inthefinalsection,thisvisioniselaboratedonwithrecommendationsfornextsteps.

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

GLOSSARY

AbbreviationDefinition

ACMCAmorphouscalcium–magnesiumcarbonate

ARCaudalfinaspectratio

CDRCarbondioxideremoval

CIConservationInternational

DICDissolvedinorganiccarbonDVMDiurnalverticalmigrationDOCDissolvedorganiccarbon

EBFMEcosystem-basedfisheriesmanagement

EBMEcosystem-basedmanagement

EwEEcopathwithEcosimfoodwebmodellingapproachHMCHighmagnesiumcalcite

IPCCIntergovernmentalPanelonClimateChange

LDOCLabileDOC

LMCLowmagnesiumcalcite

MHCMonohydrocalcite

NPZDNutrient,Phytoplankton,ZooplanktonandDetritusmodel

OCOrganiccarbon

PgCPetagramofcarbon(10^15grams=1gigaton)POCParticulateorganiccarbon

RILRelativeintestinallengthtobodystandardlengthTgCTeragramofcarbon(10^12grams)

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

Photocredit:TheWorldBank

1.METHODS&SCOPE

Theinformationprovidedinthisreporthasbeenobtainedfromfourdifferentsources:

?Aliteraturereviewwasconductedusinga“WebofScience”databasesearchinMarch2023withtwosetsof

searchterms:a)‘carbonsequestration’and‘biologicalpump’),andb)‘carbonsequestration’&‘fish’.Atotalof909referenceswereidentifiedandafterreviewingthetitleandabstracts,50paperswereselectedforacomplete

review.

?Theliteratureusedforthepresentationsoftheonline“Fish,Fisheries,andCarboninternationalworkshop”,heldlast6th,8thand9thofMarch2023,organizedbythe“OceanCarbon&Biogeochemistryprogram”andthediscussionsthattookplaceattheworkshop.

?Reviewoftheliteratureusedforthepresentationsofthe“WorkshoponAssessingtheImpactofFishingonOceanicCarbon”,held25-27April,2024,atICES,Copenhagen.Supplementedbyresultsfromdiscussionsattheworkshopandthedraftworkshopreport.

?Aroll-ontechniquewasusedtoreviewadditionalscientificpapersbasedonthereferencesofthepreviousmentionedpapers.Atotalof90additionalpaperswerereviewed.

Thisreportreviewsthecurrentscientificunderstandingoftheroleoffishinmarinecarbonsequestrationandhow

fishingaffectssequestrationprocesses.Thereviewexcludescarbonsequestrationmechanismsassociatedwithcoastalvegetationsystemssuchasmangroveforests,tidalmarshesandbenthicprimaryproducers,whichhavealreadybeenaddressedbroadlyintheliterature(Macreadieetal.,2021;Rosentreteretal.,2023;Zhongetal.,2023).Additionally,thereviewdoesnotincludethecarbonsequestrationprocessesassociatedwithaquacultureandanthropogenicocean-

basedcarbondioxideremoval(CDR)projects(Leblingetal.,2022).

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

2.INTRODUCTIONTOTHEBIOLOGIALPUMP

Theoceanplaysacriticalroleinregulatingtheclimatebyabsorbingexcessheatandcarbondioxideemissions.Overthelast60years,theoceanhasstoredapproximately23±5%ofanthropogeniccarbonemissions.Furthermore,sincethe1970s,theoceanhasabsorbedover90%oftheEarth’sexcessheat,accumulatedintheEarth’ssystem(IPCC,2021).

Theamountofcarbondioxideemittedintotheatmospherethatremainsdissolvedinseawaterisinfluencedbythreeinterlinkedprocesses:thesolubilitypump,whichisdependentonphysicochemicalconditionssuchasseawater

temperature,salinity,andtotalalkalinity;thephysicalpump,whichinvolveswaterfluxesandadvective-diffusivetransport;andthebiologicalpump(Figure1).

Figure1:Mainprocessesregulatingthemarinecarboncycling(reproducedfromLutzandMartin,2014)

Traditionally,ocean-relatedclimatechangeresearchhasfocusedonthesolubilitypumpandphysicalpump.

However,inrecentdecades,therehasbeenagrowingrecognitionoftheimportanceofthebiologicalpumpand

itsinterconnectionswiththesolubilityandphysicalpumps.Itisnowunderstoodthatthebiologicalpumpcanplay

asignificantroleintheoceansinkofanthropogeniccarbon,particularlyincertainregionalcontexts.Asaresult,

attentiononthebiologicalpumphasincreasedandislikelytocontinuetobeakeyareaofresearch(IPCC,2021;Wilsonetal.,2022).

Thebiologicalpumpreferstothevariousprocessesthattransferorganicmatterproducedbyphytoplanktonnetprimaryproductionfromthesurfaceoceantodepth,whereitcanbesequesteredformonthstomillennia.Whileresearchisongoingtoquantifythedifferentpathwaysthatcontributetocarbonsequestration,theirrelative

importanceisnotfullyunderstood(Nowickietal.,2022).

7

UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

Thebiologicalpumpreferstothevariousprocessesthattransferorganicmatterproducedbyphytoplanktonnetprimaryproductionfromthesurfaceoceantodepth,whereitcanbesequesteredformonthstomillennia.Whileresearchisongoingtoquantifythedifferentpathwaysthatcontributetocarbonsequestration,theirrelative

importanceisnotfullyunderstood(Nowickietal.,2022).

Thethreemainpathwaysofthebiologicalpumparethe‘gravitationalpump’,the‘verticalmigrationpump’andthe

‘mixingpump’(Figure1).The‘gravitationalpump’involvesthepassivesinkingofParticulateOrganicCarbon(POC)in

theformofaggregates,carcasses,andfecalpellets.The‘verticalmigrantpump’referstotheactivetransportofcarbonbyverticallymigratingzooplankton,fish,andothermarineanimals.Last,the‘mixingpump’includesthephysical

transportofbothsuspendedPOCandDissolvedOrganicCarbon(DOC)bymarinewaterfluxes.

Carbondioxideisfixedintoorganiccarbon(OC)byphytoplanktonintheeuphoticzone,whereitispartiallyincorporatedintothemarinefoodweb.Onceconsumed,itcanbeinvolvedinexcretion,exudation,respiration,consumption,

aggregation,solubilizationandgrazingprocesseswherebacteria,zooplankton,fishandothermarineanimalsare

involved(Figure2).Whilemostoftheorganicparticlesarerecycledinsurfacewaters,asmallfractionsinksina

proportionthatiscalled‘exportrate’fromtheeuphoticzone,themixedsurfacelayer,oracrossanarbitraryhorizonoftensetaround100meters.Thebiologicalpumpexportsapproximately10(PgCyr?1(Nowickietal.,2022)tothe

deeperocean,withtheestimatedfish-basedcontributionbeingaround1.5±1.2(PgCyr?1(Sabaetal.,2021).However,itisimportanttonotethatthereisahighuncertaintyinestimationoffishexportflux,aggravatedbyfishhavingthehighestbiomassesincoastalandshelfareaswhereknowledgeaboutcarbonsequestrationiscursoryatbest.

ThesinkingfluxofPOCexportedfromthesurfaceoceanisrapidlyattenuatedduetoacombinationofabioticandbioticprocesses.Fragmentationbywaterturbulence,andzooplanktonandmicrobialactionconvertlarge,rapidlysettling

particlesintosmaller,moreslowlysettlingparticles,therebyreducingtheverticalfluxofPOC.Bioticprocessessuch

asmicrobialdegradationandconsumptionbyorganismsreducetheamountofsinkingPOCandsoreducetheflux,

convertingpartofittoDissolvedInorganicCarbon(DIC)throughrespiration(Countrymanetal.,2022).Theamountof

POCreachingthedeepoceanisonlybetween0.2and2%oftheexportedcarbon,thatis(0.02-0.2)PgCyr?1,somostofthesequesteredoceaniccarbonisDIC(Siegeletal.,2023).Thedepthandlocationatwhichorganiccarbonistransportedandremineralized,andthewaterfluxesinthearea,determinehowlongthecarbonissequesteredintheocean(Saba

etal.,2021).Ingeneral,carbonissequesteredforlongerthanayearbyparticlesthatpenetratebeneaththewintertimemixedlayer,andforuptocenturiesbyparticlesthatreachdeepwatermassesbelow1000m(Boydetal.,2019).

AccordingtoNowicki(2022),theannualglobalcarbonsequestrationbythebiologicalpumpis1293(1302-1281)PgC,withanaveragesequestrationtimeof127(133-122)years,whichiscoherentwiththeinventoryofDIC(Carteretal.,2021)fromrespiredorganicmatter:1300(±230)PgC,beingthegravitationalpumpthemoreimportantpathway(Table1).

Table1:Sequestrationandsequestrationtimeofthebiologicalpumppathways

Sequestration(PgC/year)

Sequestrationtime

(years)

Source

Mixingpump

102(100-106)

54(48-64)

Nowickietal.,2022

Gravitationalpump:aggregatePOC

207(98-293)

185(170-202)

Nowickietal.,2022

Gravitationalpump:fecalpelletPOC

833(746-943)

136(129-143)

Nowickietal.,2022

Migrantpump

150(83-188)

150(94-213)

Nowickietal.,2022

Undifferentiated

1300(±230)

Carteretal.,2021

~100m

~1000m

Mixingpump

DOCandPOCphysicaltransport

DOCandPOCphysicaltransport

DOCandPOCphysicaltransport

Photosynthesis-DIC

Bacteria

Phytoplankton

Fish

Fishfecalpellets

-fast

verticalspeed

Fish

RespirationDIC

Bacteria

Zooplanktonfecalpellets

RespirationDIC

Gravitationalpump(passivepump)

Respiration-DIC

Zooplankton

Sinking

phytoplankton

&

zooplankton

carcases

DOCandPOCproductionAggregationsZooplanktonfecalpellets

sinkingfsh

Aggreationsandfecalpellets

carcasses

Solubilization

&

disaggregation

Consumption

Zooplankton

DOCandPOC

Uptake

Fishfecalpellets

Solubilization

&

disaggregation

Bacteria

Uptake

DOCandPOC

Fish

Metazoans

Whales

-Largepelagicfsh

-Tactilepredatorsi.e.jellyfsh-Mesopelagicfsh

BathypelagicFish

Verticalmigrationpump(activepump)

Zooplankton

-Foragefish

-meso-

zooplankton-macro-

zooplankton

Depth

Euphoticzone

sequestrationtime1-10y

sequestrationtime10-100y

Mesopelagiczone

sequestrationtime100-1000y

Deepseazone

Figure2:Mainpathwaysandprocessesofthebiologicalpumpwithaspecificfocusonfish.DOC=Dissolvedorganiccarbon.POC=particulateorganiccarbon.DIC=dissolvedinorganiccarbon.Yellow=fishrelated(AdaptedfromSiegeletal.2021)

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

Thequantificationofcarbonfluxesandsequestrationprocessesintheoceanischallengingduetolimitationsin

theavailabledataforeverystepofthemarinecarboncycle.Thevariabilityoftheseprocessesunderdifferent

environmentalconditionsaddsfurthercomplexity.Additionally,thedifficultyofintegratingdifferenttypesofmodels,whichmayusedifferentassumptionsandinputdata,canleadtoadditionaluncertaintyinthefinalestimates(Figure3).

Metabolic

“production”model

?DOC,DIC,POCand

carbonatesproduction?Carcassesproduction

Fishingactive

gearsinteractions

withsediments

?Physicalprocesses

?Ecologicalimplications

Physicaltransport

?Watertransportservices

?Fishverticalmovements

Ecosystemmodel

?Mutlispeciesdynamicsandinteractions

Biochemicalmodel

?Particaltransformationsinthewatercolumn

?Particaltransformationsinthesediments

?Dissolved

▲

transformations

Environmental

conditions

?Temperature

?Salinity

?

......

Figure3:Modelsneededtoquantifythebiologicalpumpcarbonsequestrationofmarineecosystems.

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

3.MODELINGTHEFISHCARBONPUMP

Asdescribedabove,phytoplankton,zooplanktonandbacteriaplayamajorroleinthefunctioningofthebiologicalpump,butinadditionmarinevertebrates,andespeciallyfish,throughmultipleprocessesalsohavearoleinmarinecarbonsequestration.

3.1Metabolic'production'processes

?POCproduction:Fisheatandrepackagefoodintocarbon-richfecalpelletsthatsinkrapidlythroughthewatercolumnuntilapartreachesthebottomoftheocean.Atthesametime,fishalsocontributetoPOCdegradationthroughconsumptionprocesses.

?DOCandDICproduction:Fish,whenalive,produceDOC,andthroughrespirationDIC,thatisintegratedinthewatercolumn,wherebiologicalandphysicalprocesseswilldeterminatetheirstoragetimeintheocean.

?Carbonateproduction:Fishproducecarbonate(CaCO3)1asaby-productoftheosmoregulationprocess.

?Carcassproduction:Whenfishandotherlargemarinevertebratesdie,theircarcassessinkrapidlytotheseafloor,wherethecarbonbiomassistransformed(andpartiallypredatedbyotherorganisms)andinpartpotentially

buried.

?Livingbiomasscarbon:Alllivingthingsarepartiallymadeofcarbonandthusserveascarbonreservoirsthroughtheirlifespans.Thelargerandmorelong-livedanorganismis,andthelargerapopulationis,themorecarbonisstored.

?Otherindirectrelatedprocesses:

°Fertilizingspecies:manymarinevertebrates,suchaswhales,haveactivehorizontalandverticalmovements.Vertically,whalesdivetofeedandreturntothesurfacetobreathe.Whileatthesurface,theyreleasebuoyantfecalplumesthatarerichinnutrientsthatphytoplanktonneedforgrowth,stimulatingcarbondioxide

capture.Horizontally,manywhalespeciesundertakeseasonalmigrationsfromnutrient-richfeedinggroundstonutrient-poorbreedinggrounds.Atthesebreedinggrounds,whalesreleasenitrogen-richurea,whichcanpromotephytoplanktongrowthandstimulatecarbondioxidecapture.

°Coastalcascadecarbon:Marinepredatorshelpmaintainthecarbonstoragefunctionofcoastalvegetationbykeepingherbivorepopulationsincheck.Thisprocesscanberelevantforcoastalbluecarbonandseaweed(Atwoodetal.,2015).

°Biomixingcarbon:Theswimmingmovementsofmarineanimalscanstirupnutrientstowardssurfacewaters,whichphytoplanktoncanusetogrow,absorbingcarbonintheprocess.

Theprocessesdescribedhavedifferentlevelsofuncertaintyandrelevanceforcarbonsequestration.

3.2Fisheries

Unlikefarming,whichisgenerallynotconsideredacarbonsinkunlessspecificallydesignedtocaptureexcesscarbon(e.g.,Leifeld2023),fisheriesdirectlyandindirectlyinfluenceanumberoflarge-scale,long-termoceaniccarbon

sequestrationpathways(Krabbeetal,2022)andtherefore,fisheriesmanagementmayaidtoprovidesomelevelofcontroloncarbonsequestration.

Fishingactivitiesinteractdirectlywiththeprocessesdescribedabovebyextractingbiomassandchangingthefoodwebstructureandfunctioningofecosystems.Asaconsequence,fisheriesnotonlyaffectvolumesoflivingbiomassorcarcasses,butaffectfishPOC,DOCandDICtotalproductionandtheindirectprocessdescribedearlier.

1Atlong-termcarbonatedilutesandbecomesdissolvedinorganiccarbon/articles/s41561-021-00743-y

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UnderstandingtheRoleoftheFisheriesandAquacultureinCarbonSequestration

Further,somefishingpractices,suchasbottomtrawlinghavedirectimpactsontheseafloorandcanpotentially

reintroducecarboninthesedimentintothewatercolumn,therebyimpactingcarbonsequestrationbyalteringtheseabottom(Figure4).

Figure4:Directandindirectimpactsoffishingoncarbonsink:1)Fertilizingspecies,2)egestionoffast-sinkingcar-

bon-richfecalpellets,3)harvestinglow-midtrophiclevelpellet-producingspecies,4)removingspecieslivingneartheseabedwherethesinkofcarbonwillbeshort,5)sedimentdisturbancefromgroundfishharvesting,6)removingresi-

dentormigratorymesopelagicspeciesthatcontributetothecarbonsink,7)removinglargefishandwhalesreducing

largefallsofdeadorganicmattertothedeepseaandsediment.Indirectimpacts:8)causingtrophiccascadeswhen

removinghightrophiclevelspeciesimpactinglowtrophiclevelcommunitiesthatsinkcarbon,9)removingpreyitemsforfertilizingspecies,10)killingpredatorsthatmayotherwisefertilizetheoceansandmaintainabalancedfoodweb,11)releaseofdiscardswhichcouldcauselocalizeddeadzones(AdaptedfromCavanandHill2022)

Thefollowingsectionexploresthemaindirectprocessesbywhichfisheriescontributetocarbonsequestration.Itdescribestheseprocesses,reportssomekeyreferencevalues,andpointsoutsomeofthemaindiscussionsanduncertainties.

3.3deFinitionoFkeystocksandFlows

Figure5showsasimplifiedgeneralschemeofthedifferentsectionsthatafish-carbonmodelrequires.Thescheme

assumesthebiomassdistributionisknownforthekeyfishgroupsofspeciesinanecosystemthatcanbeobtained,forexamplefromafood-webmodel.

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UnderstandingtheRoleoftheFisheriesa