global carbon cyclevolumetric data (1931 observations) r2 = 0.44 1.5 2 2.5 3 0.51 1.52 2.5 3...

15
Agouron_PW_lecture_3 1/15 THE OCEAN CARBON BUDGET: CAN WE MAKE SENSE FROM NONSENSE A) THE STRUCTURE OF THE OCEANIC BUDGET Atmosphere Open ocean Coastal ocean Land Marginal benthos Estuaries P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle Photosynthesis/respiration cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle P/R cycle Photosynthesis/respiration cycle Organic fluxes Organic fluxes CO 2 fluxes CO 2 fluxes Global Carbon Cycle

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  • Agouron_PW_lecture_3

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    THE OCEAN CARBON BUDGET: CAN WE MAKE SENSE FROM NONSENSE

    A) THE STRUCTURE OF THE OCEANIC BUDGET

    Atmosphere

    Open oceanCoastal oceanLand

    Marginal benthos

    Estuaries

    P/R cycleP/R cycle P/R cycle

    P/R cycle

    P/R cycle

    P/R cycle Photosynthesis/respiration cycle

    P/R cycleP/R cycle P/R cycle

    P/R cycle

    P/R cycle

    P/R cycle

    P/R cycleP/R cycleP/R cycleP/R cycle P/R cycleP/R cycle

    P/R cycleP/R cycle

    P/R cycleP/R cycle

    P/R cycleP/R cycle Photosynthesis/respiration cycle

    Organic fluxesOrganic fluxes

    CO2 fluxesCO2 fluxes

    Global Carbon Cycle

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    SourceNet productionNet consumptionNet heterotrophicPR

    CO2source/sink

    Net CO2 metabolism

    Net O2 metabolism

    Trophic stateP v R balance

    SourceNet productionNet consumptionNet heterotrophicPR

    CO2source/sink

    Net CO2 metabolism

    Net O2 metabolism

    Trophic stateP v R balance

    The Biogeochemical Cycle – Closed System

    Photosynthesis

    CO2 + H2O = “CH2O” + O2

    Respiration

    All units are Tmol C/a

    Light

    Heat

    The closed system cannot sustain PI, then P>R net autotrophicI>E, then R>P net heterotrophic

    ImportsImports ExportsExports

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    B) OVERALL MASS BALANCE

    P/R cycleP/R cycle

    Atmosphere

    23 T

    mol

    C/a

    23 T

    mol

    C/a

    Net Heterotrophic ocean

    P/R cycleP/R cycleP/R cycleP/R cycle

    Estuaries

    35 Tmol C/a35 Tmol C/a12 Tm

    olC/a

    12 TmolC

    /a35 Tmol C/a35 Tmol C/a

    43 T

    mol

    C/a

    43 T

    mol

    C/a

    23 Tmol C/a23 Tmol C/a

    Conclusion:

    Net autotrophic land feeding a

    Net heterotrophic ocean

    Terrestrial P/R cycle. 10,000 Tmol C/a

    20 T

    mol

    C/a

    CH420 T

    mol

    C/a

    20 T

    mol

    C/a

    CH4

    5,85

    0 Tm

    olC

    /a5,

    850

    Tmol

    C/a

    6,00

    0 Tm

    olC

    /a6,

    000

    Tmol

    C/a

    Land Coastal ocean + Open ocean

    All units are Tmol C/a

    Mangroves Coral reefs

    Macroalgae

    Sea grasses

    Marginal Benthic Ecosystems

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    P & R balance in marginal benthic ecosystems (Duarte et al. 2005)

    Export into the coastal zone = 860-(609+9.3) = 250 Tmol C/a

    9.3609860

    -166135Unvegetatedhabitats

    -7986Coral Reefs-247432Macroalgae

    2.31952Sea Grasses567120Salt marshes23135Mangroves

    BurialTmol C/a

    RespirationTmol C/a

    PhotosynthesisTmol C/a

    9.3609860

    -166135Unvegetatedhabitats

    -7986Coral Reefs-247432Macroalgae

    2.31952Sea Grasses567120Salt marshes23135Mangroves

    BurialTmol C/a

    RespirationTmol C/a

    PhotosynthesisTmol C/a

    P + IR + IA + IC = R + ES + EA E-I

    35 + 2 15 + 2 = -20 35 + 2 + 250 15 + 2 = -270

    Thus, At P = R-20 Tmol C/a; the oceans are NET Heterotrophic Assume P ~ 5,000 to 10,000 Tmol C/a Percentage heterotrophy = 0.2 to 0.4%, well beyond field techniques to detect

    Imports ExportsImportsImports ExportsExports

    At P + = R - 270 Tmol C/a; t the oceans are NET Heterotrophic Assume P ~ 5,000 to 10,000 Tmol C/a Percentage heterotrophy = 2.5 to 5%, difficult for field techniques to detect

    Imports ExportsImportsImports ExportsExports

    287 27

    37 27

    R>R

    R>R

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    Wetlands

    Net Autotrophic

    Net Heterotrophic3500m

    150m

    1000m

    Land

    Sediments

    SedimentsEpipelagic Ocean

    Lakes

    Bathypelagic Ocean

    Sediments

    Sediments

    Mesopelagic Ocean

    Coastal Zone

    Estuaries

    Atm

    osph

    ere

    Rivers

    SedimentsCoastal Margins

    Net heterotrophy is a widespread and repeated observation in aquatic ecosystemsWhy? How?

    See also Duarte and Prairie (2005) Prevalence of Heterotrophy and Atmospheric CO2 Emissions from Aquatic Ecosystems. Ecosystems 8 862-870

    C) INTERNAL DISTRIBUTION - ANALYSIS OF FIELD OBSERVATIONS DISPARITY BETWEEN IN SITU AND IN VITRO OBSERVATIONS

    del Giorgio, et al. (1997), Respiration rates in bacteria exceed plankton production in

    unproductive aquatic systems. Nature 385, 148-151 Duarte, C. M. and Agusti, S. (1998), The CO2 balance of unproductive aquatic

    ecosystems. Science. 281 234-236. Williams, P. J. le B. (1998), The Balance of Plankton Respiration and Photosynthesis

    in the Open Oceans. Nature 394 55-57.

    Fit to the equation R = aPb, which enables us to solve for P = R,

    i.e. P=aPb, a = P/Pb = P(1-b), then P=a1/(1-b)

    - 2

    - 1

    0

    1

    2

    - 2 - 1 0 1 2L o g 1 0 ( P h o t o s y n t h e t ic R a t e )

    Log 1

    0(Res

    pira

    tion

    rate

    )

    - 2

    - 1

    0

    1

    2

    - 2 - 1 0 1 2

    L o g 1 0 ( P h o t o s y n t h e t ic R a t e )

    Log 1

    0(R

    espi

    ratio

    n ra

    te)

    N e t H e t e r o t r o p h y

    N e t A u t o t r o p h y

    R = PF i tte d L i n e

  • Agouron_PW_lecture_3

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    Units

    a as

    gO2/m3d

    b

    P=R as

    gO2/m3d

    P=R as

    mmolO2/m3 d

    Observations

    Del Giorgio et al., 1997

    7.24 0.62 183 15 Only systems with net productivity >10 mmol C/m3 d are autotrophic. Most of the oceans fall below 10 mmol C/m3; surface values at HOTS are c. 1 mmol C/m3 d

    Duarte & Agusti, 1998

    Coastal water 1.1 0.72 1.62 44

    Ocean water 0.2 0.5 0.035 1.25

    Overall oceans 0.27 0.615 0.033 1.04

    The oceans as a whole are in metabolic balance i.e. ΣP=ΣR. 25 out of Longhurst’s 56 biogeochemical zones (80% ocean surface) are net heterotrophic, sustained by the remaining 20% of the ocean surface

    Williams, 1998 No correlation – r2 = 0.07

    P=R at rates way beyond those observed

    There is no evidence for the large regional imbalances

    Autotrophic zones: Heterotrophic zones:

    The Predicted Distribution of Autotrophy and Heterotrophy from the Duarte & Agusti Equation

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    The Problem The Prediction Calculated Annual Net Production = -8 mol C/m2d The Observation In situ rates (see table below) c. +3 mol C/m2d

    Author Approach Annual Net Production (mol C m-2 a-1)

    Emerson et al (1997) Surface oxygen budget +2.7±1.7

    Benitez-Nelson et al (2001) Organic carbon export rates, based on 234Th budget, DOC gradients and zooplankton migration rates

    +2.4±0.9

    Sonnerup et al (1999) Subsurface O2 utilisation rates +2.2±0.5

    Quay and Stutsman (2003) DIC and δ13C measurements +2.7±1.3

    Juranek and Quay (2005) 18O2 and O2/Ar ratios +3.2

    D) ACCOUNTING FOR THE IMBALANCES The imbalance can be derive from

    1. Sampling & Interptetation (Williams) 2. Missed Organic Sources (Duarte) 3. Errors in in vitro Method (Williams)

    1) Sampling & Interptetation

    Spatial Depth – P>R at the surface, R>P at depth Regional – transfers between productive and unproductive zones

    Temporal – Seasonal – accumulation of DOC in the productive period Subsampling – bursts of photosynthesis, integration by respiration

    Spatial – depth (Williams, 1998)

    y = 0.4107x - 0.0729R2 = 0.6287

    -0.8

    -0.6

    -0.4

    -0.2

    0

    0.2

    -1.2 -0.8 -0.4 0

    Log Photosythetic rate (mmolsO2/m3d)

    RespP=R line

    Log

    Res

    pira

    tion

    rate

    (mm

    olsO

    2/m

    3d)

    Analysis of P vrs R for Station Aloha

    020406080

    100120140160

    0 0.01 0.02 0.03

    Rate

    Dep

    th (m

    )

    GPP

    Resp

    P and Predicted R values

    0

    20

    40

    60

    80

    100

    120

    -0.5 0 0.5 1 1.5

    Rates (mmol O2/m3d)

    Dep

    th (m

    )

    GPPCal RespNCP

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    Temporal – seasonal (Serret et al 1999)

    Algal Photosynthesis and Community Respiration ( 30% Algal)

    0

    50

    100

    150

    0 100 200 300 400Day of Year

    Rat

    es

    Photosynthesis

    Respiration

    P/R ratio through a bloom rise and fall

    0

    10

    20

    30

    40

    50

    0 25 50 75 100Photosynthetic Rate

    Res

    pira

    tion

    Rat

    e

    P/R ratio through a bloom rise and fall

    0

    1

    2

    0 1 2Log Photosynthetic Rate

    Log

    Res

    pira

    tion

    Rat

    e

    Seasonal DOC accululationDOC formation Microbial recycling

    Bloom P>R

    Spring/Summer

    Regeneration R>P

    Autumn/Winter

    HOT study (Williams et HOT 2004)

    There appears to be no seasonal storage in the DOC component.

    -2.0

    -1.0

    0.0

    1.0

    2.0

    -2.0 -1.0 0.0 1.0 2.0

    Log10(photosynthetic rate)Lo

    g 10(

    resp

    iratio

    n ra

    te)

    1:1 LineOLSMRA

    y = 0.41xP + 0.1y = 0.62xP + 0.04

    Photosynthesis vrs Respiration Volumetric data (1931 observations)

    R2 = 0.44

    0.5

    1

    1.5

    2

    2.5

    3

    0.5 1 1.5 2 2.5 3

    Log10 (Σphotosynthetic rate) as mmoles m-2 d-1

    Log1

    0 (

    resp

    irato

    ry ra

    te) a

    s m

    mol

    es m

    -2 d

    -1

    1:1 lineOrdinary least squaresMajor reduced axis

    Photosynthesis vrs RespirationAreal data (218 observations)

    R2 = 0.072

    Seasonal Cycle of Depth-integrated Rates

    -100

    -50

    0

    50

    100

    HO

    T 12

    6 ( 1

    6/05

    /200

    1)

    HO

    T 12

    7 ( 1

    4/06

    /200

    1)

    HO

    T 12

    8 ( 1

    1/07

    /200

    1)

    HO

    T 12

    9 ( 0

    8/08

    /200

    1)

    HO

    T 13

    1 ( 2

    3/10

    /200

    1)

    HO

    T 13

    2 ( 1

    7/11

    /200

    1)

    HO

    T135

    ( 21

    /02/

    2002

    )

    HO

    T136

    ( 13

    /03/

    2002

    )

    HO

    T 13

    7 ( 2

    1/05

    /200

    2)

    Rat

    es (m

    mol

    m-2

    d-1

    )

    GPP Depth IntegralNCP Depth IntegralResp Depth Integral14C Rate Integral

    Seasaonal Profile of DOC (0-150m)

    020406080

    100120140

    0 2 4 6 8 10 12Month

    DO

    C (u

    M)

  • Agouron_PW_lecture_3

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    Temporal – subsampling frequency (Karl, D.,et al. 2003)

    2) Missed Sources Regional – transfers between productive and unproductive zones – Duarte’s perception (Duarte and Agusti, 1998).

    Do we have a Autotrophic Coastal Ocean Subsidising Heterotrophic Open Ocean

    Early Work (pre-1990) suggested this was so:

    Steele (1974) and Walsh et al’s(1988) work suggested some 45% of coastal oceanic production was exported

    But the conceptual models were flawed as they omitted microbial respiration

    Williams, P. J. le B. and Bowers, D. G. (1999) Regional carbon imbalances in the

    oceans. Science 284 1735b. Duarte, C. M., Agusti S, del Giorgio, P. A., and Cole, J. J . (1999) Regional carbon

    imbalances in the oceans. Science 284 1735b.

    Autotrophic zones: Heterotrophic zones:

  • Agouron_PW_lecture_3

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    Transport of DOC & POC DOC i) The DOC from the rivers (c. 18 Tmol C/a) is

    generally assumed to pass through the coastal zone to the open ocean unmodified

    ii) From inshore/offshore DOC gradients Duarte estimates a offshore flux of 450 Tmol C/a flux (20x greater) –

    POC moves down the continental slope into the mesopelagic: Wollast - 182 T mol C/a; Ducklow & McCallister - 100-200 T mol C/a

    Atmospheric Transport (Dachs et al., 2005)

    -32 -30 -28 -26 -24 -22 -20 -18 -16 -1416

    18

    20

    22

    24

    26

    28

    -145-70

    -99-39-51-43

    -124-57

    -112

    -81 -58 -138 -91-210 -243

    64

    1967

    7819437426

    133

    78 63 94 76 64192

    386

    602

    179

    13

    77

    6

    -258

    -611

    -140

    -15

    -49

    -36

    28

    26

    24

    oN 22

    20

    18

    16-32 -30 -28 -26 -24 -22 -20 -18 -16 -14

    oW

    -32 -30 -28 -26 -24 -22 -20 -18 -16 -1416

    18

    20

    22

    24

    26

    28

    -145-70

    -99-39-51-43

    -124-57

    -112

    -81 -58 -138 -91-210 -243

    64

    1967

    7819437426

    133

    78 63 94 76 64192

    386

    602

    179

    13

    77

    6

    -258

    -611

    -140

    -15

    -49

    -36

    28

    26

    24

    oN 22

    20

    18

    16-32 -30 -28 -26 -24 -22 -20 -18 -16 -14

    oW Estimates range:

    coastal regions - mean uptake of c.500 m moles C m-2 d-1- mean emission of 440 m moles C m-2 d-1

    With a mean for the region of 28 m moles C m-2 d-1 ≡ 120gC m-2 a-1

    Which is massive, considering productivity rates may be in the region of 150-300 gC m-2 a-1

    Total emission = 0.64 Gt C yr = 50 Tmol (C/a 50x1012 mol C/a)

    Raises the question: where does it come from: it’s 10% of fossil fuel consumption

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    3) Errors in in vitro Methodology We are getting repeated and reliable reports of in situ O2-determined rates, far exceeding in vitro 14C and ∆O2 determined rates that we need to look hard at our methodology a) So called “Bottle effects” b) Incubation procedures E) BALANCING THE OCEANIC BUDGET Problems in a number of related areas: 1) Discrepancies in the Global Estimate of P and R 2) Different Conclusions over the distribution of P-R balance within the Oceans 3) Wide range of estimated of the transport between various pools

    1) Discrepancies in the Global Estimate of P and R a. Methodological errors in estimating P (& possibly R) b. Small, and probably biased, database for R

    Coastal ocean + Open oceanLand

    P/R cycle

    35 Tmol C/a

    Coastal ocean + Open oceanLand

    P/R cycle

    35 Tmol C/a35 Tmol C/a

    A c.10,000 T mol C/a deficit (75% of turnover) would suggest a major budgetary problem! Respiration (O2) = 13,000 T mol C/a

    Photosynthesis (14C) = 3,500 T molC/a

    12 Tmol/a

    12 Tmol/aOne/both of our methods is giving the wrong answer

    1) Errors in the interpreting the 14C-technique and global projection: x2-x3

    2) O2 data-base too small for accurate global estimates

    Geochemical estimates (16O2/17O2/18O2 disequilibrium and O2 flux) suggest higher figure is more probable

  • Agouron_PW_lecture_3

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    Errors Associated with the 14C-technigue

    With the 14C technique we are not comparing like with like:

    1) We should be comparing total photosynthesis (GPP) with total respiration (R)

    The 14C-algal measures something between GPP and NPP (perhaps even NCP)NPP = GPP – Ralgal

    So we are comparing: GPP – Ralgal with Ralgal+ Rheterotroph

    As algal respiration through the water column is c. 40% of GPPwe get a substantial error

    2) Loss of DOC by excretion is overlooked

    We can attempt to make corrections:1) Algal respiration at high P rates algal R≈0.1*P, but through the

    water column euphotic zone R≈0.4*P is probably a reasonable estimate

    2) Estimates of excretion are commonly believed to be ≈0.15*P, but figures ≈0.5 *P have been suggested

    @ 15% Exc=0.15*P & R=0.4*P; 2,500 T mol C a-1 converts to 4,900 T mol C a-1

    @ 50% Exc=0.50*P & R=0.4*P; 2,500 T mol C a-1 converts to 8,300 T mol C a-1

    Thus we can make some headway to match a respiration figure of 13,000 mol C a-1, but we need to make some uncomfortably extreme assumptions

    At best it only can account for part of the solution

    2) The O2 respiration database is too small to attempt global estimates

    Conclusions

    Global Distribution of Respiration Measurements (white dots)

    Global Distribution of Respiration Measurements (white dots)

    No Data

    No Data

    No DataNo

    Data

    No Data

    No Data

    No Data

    No Data

    The Current (as of 2004) Respiration Data base

  • Agouron_PW_lecture_3

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    Low estimate High estimate Geomean T mol C/a T mol C/a T mol C/a COASTAL ZONE INPUT INTO COASTAL REGIONS Rivers 35 35 35 Atmosphere 1.5 250 (net) 20 Marginal benthos 1 250 16 OUTPUTS FROM COASTAL ZONE Atmosphere 1 1 1 Sediments 9 15 12 Ocean - Epipelagic 18 450 90 Ocean - Mesopelagic 1 180 13 PRIMARY PRODUCTION 600 1200 850 EPIPELAGIC OPEN OCEAN INPUTS INTO EPIPELAGIC OCEAN Coastal zone 18 450 100 Atmosphere 1 250 20 OUTPUTS FROM EPIPELAGIC OCEAN Atmosphere 1 1 1 Mesopelagic 100 500 225 PRIMARY PRODUCTION 3,500 10,000 600 MESO+BATHY-PELAGIC OPEN OCEAN INPUTS INTO THE MESOPELAGIC Coastal Zone 1 450 20 Epipelagic 100 500 225 OUTPUTS FROM BETHYPELAGIC Sediments 2 2 2

  • Agouron_PW_lecture_3

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    LOW ESTIMATESAtmosphere Atmosphere

    1.5 1.5 1 1Margins 1

    Coastal 18 EpipelagicRivers 35 Balance 8 Balance -82

    Net hetero 1% Net auto -2%1 100 Mesopelagic

    9

    2Sediments

    Coastal Zone Open Ocean

    Sediments

    HIGH ESTIMATES

    Atmosphere Atmosphere250 1 250 2

    Margins 250

    Coastal 450 EpipelagicRivers 35 Balance -113 Balance 248

    Net auto -9% Net hetero 2%182 450 Mesopelagic

    15

    2Sediments

    Sediments

    Coastal Zone Open Ocean GEOMETRIC MEAN ESTIMATES

    Atmosphere Atmosphere20 1 20 2

    Margins 16

    Coastal 90 EpipelagicRivers 35 Balance -45 Balance -107

    Net auto -5% Net auto -2%13 225 Mesopelagic

    12

    2Sediments

    Sediments

    Coastal Zone Open Ocean

    Summary of Mass Balances ESTIMATE COASTAL ZONE UPPER OPEN OCEANLOW Net Hetero (1%) Net Auto (2%) HIGH Net Auto (9%) Net Hetero (2%) GEOMEAN Net Auto (5%) Net Auto (2%)

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    Essential reading:

    del Giorgio, et al. (1997) Respiration rates in bacteria exceed plankton production in unproductive aquatic systems. Nature 385, 148-151

    Duarte, C. M. and Agusti, S. (1998) The CO2 balance of unproductive aquatic ecosystems. Science. 281 234-236.

    Williams, P. J. le B. (1998) The Balance of Plankton Respiration and Photosynthesis in the Open Oceans. Nature 394 55-57.

    Supplementary reading: Duarte and Prairie (2005) Prevalence of Heterotrophy and Atmospheric CO2

    Emissions from Aquatic Ecosystems. Ecosystems 8 862-870 Serret et al (1999) Seasonal compensation of microbial production and

    respiration in a temperate sea. MEPS 187 43-57 Williams, Peter J. le B., Morris Paul J and. Karl David M (2004) Net

    Community Production and Metabolic Balance at the Oligotrophic Ocean Site, Station ALOHA. Deep Sea Res 51: 1563-1578

    Karl, D.,M., Laws, E. A., Morris, P, J., Williams, P. J. le B and Emerson S. (2003) Metabolic balance in the sea. Nature 426 32