CarboOcean-2006 Coral Reefs and the Carbon Cycle Joanie Kleypas National Center for Atmospheric Research NOAA Background on Reefs and Carbon More than

CarboOcean-2006

Coral Reefsand the Carbon Cycle

Joanie Kleypas National Center for Atmospheric Research

NO

AA

Background on Reefs and Carbon

More than Reefs?

Reef CaCO3 Production & Accumulation

Controls on Reef Calcification

CarboOcean-2006


NO

AA


More than Reefs?



CarboOcean-2006

Coral Reefs- Organic Carbon Production -

Organic Carbon Production in Low Nutrient Waters

1. High organic production (79–584 g C m–2 y–1)

2. Topographically induced upwelling, internal tidal bores; ‘endo-upwelling’

3. Efficient production of organic carbon (Nitrogen fixation)

C : N : P Coral reefs: 550:30:1 Open ocean: 106:16:1

Smith, 1988

CarboOcean-2006

Gross Production

Res

pir

atio

n

Pg/RReef Flats: 1.07 ± 0.1(n=43)

Reef System: 1.28 ± 0.2(n=9)

Organic C metabolism of coral reefs is balancedor slightly autotrophic

Coral Reefs- Organic Carbon Production -

(Gattuso, Frankignoulle, Wollast 1998)

CarboOcean-2006

Coastal Ecosystems - Organic Carbon Production -


Gross Prod.

mol C m–2 y–1

Area

106 km2

NEP

Tmol C y–1

Estuaries 22 1.4 -8

Macrophyte-dominated

87 2.0 37

Coral Reefs 144 0.6 6

Salt marshes 185 0.4 7

Mangroves 232 0.2 18

Remaining shelf

18 21.4 171

CarboOcean-2006

Coastal Ecosystems - Organic Carbon Production -


Gross Prod.

mol C m–2 y–1

Area

106 km2

NEP

Tmol C y–1

Estuaries 22 1.4 -8

Macrophyte-dominated

87 2.0 37

Coral Reefs 144 0.6 6

Salt marshes 185 0.4 7

Mangroves 232 0.2 18

Remaining shelf

18 21.4 171

CarboOcean-2006

Habitat Area CaCO3 CaCO3 CaCO3

flux glob. prod. accum.x106 km2 g/m2/y 1012 mol/y 1012 mol/y

reefs 0.6 1500 9 7

banks 0.8 500 4 2 carbonate 10.0 20-100 6 3shelves

open ocean 290.0 20 60 11

Coral Reefs - Inorganic Carbon Production -

(Milliman 1993; Milliman & Droxler 1996)

CarboOcean-2006

Coral ReefHypothesis

Berger 1982; Opdyke & Walker 1992; Walker & Opdyke 1995

Kleypas 1997 → shelf flooding initiated pulse in CaCO3 but not until 8000 yBP

Archer et al. 2000 → can explain portion – but not all – of post-glacial CO2 rise

Ridgwell & Kennedy 2004 → 20 ppm CO2 increase in late Holocene

Ridgwell and Kennedy 2004

Changes in basin-shelf partitioning of CaCO3 production caused glacial-interglacial fluctuations in atmospheric CO2

CarboOcean-2006

Estimates of Shelf CaCO3 FluxFlux Rate

g m-2 y-1

Area

106 km2

Accumulation

1012 mol y-1

Turekian 1965 negligible NA NA

Garrels & Mackenzie 1971 negligible NA NA

Chave 1972 1,000-20,000 NA NA

Milliman 1974 350 1.4 5

Smith 1978 * 1,000 0.6 6

Schlager 1981 1,450 0.6 8.1

Kinsey & Hopley 1991 * 1,812 0.6 11

Milliman & Droxler 1996 * 1,500 0.6 7

Kleypas 1997 * light-dependent 0.6-0.9 9-10

Opdyke & Schimel 2000 * 1,600 0.8 14-20

* Reef environments only Modified from Opdyke & Schimel 2000

CarboOcean-2006

Smith & Kinsey’s (1976) avg calc’n rate:20% reefs @ 4000 g m-2 y-1 80% lagoons @ 800 g m-2 y-1

1500 g m-2 y-1

Net CaCO3 production

600,000 km2

10% dissolved/exported10% biological erosion/“corrosion”

Net CaCO3 accumulation

0.9 x 109 tons CaCO3 y-1

20%

0.7 x 109 tons CaCO3 y-1

Smith’s (1978) reef area estimate

CarboOcean-2006


NO

AA


More than Reefs?

CaCO3 Production & Accumulation


CarboOcean-2006

“… cold water corals may cover as large an area as … warm-water corals that form shallow reefs” (Williams et al., Eos 21 Nov 2006)

How Good are Estimates of Shelf

Accumulation?Coral reefs are the “gold standard” of high carbonate production

– Almost all estimates of shelf carbonate production have concentrated on coral reefs

“The mean annual calcification of L. corallioides populations … are similar to those reported for tropical coralline algae …” (Martin et al. 2006)

“These production and accumulation rates are similar to the lower end of such rates from tropical coral reef environments” (Bosence and Wilson 2003)

CarboOcean-2006

What about non-tropical carbonates?

Milliman & Droxler 1996 estimated that for non-tropical shelves: – calcification rates < 20% of tropical

carbonates

– net accumulation ~ 30% of tropical carbonates

How Good are Estimates of Shelf

Accumulation?

These data are even lessconstrained than for reefs

CarboOcean-2006

Types of Shallow Water Carbonates

System:

Coral Reefs

Halimeda banks

Coralline algae & rhodolith beds

Cold-water reefs

Cool-water carbonates

Ooid shoals

Oyster banks

…. etc

Organism:Corals

Calcareous algaeCoralline red algae

Green algae Halimeda/Penicillus

Forams

Sponges

Bryozoans

Brachiopods

Molluscs

Annelids

Echinoderms

Arthropods

CarboOcean-2006

Calcification Rates of Benthic CalcifiersCalcifier Organism G

g m-2 y-1

Reference

Corals Porites sp. Skel. ext. x dens.

(per surf. area of coral)

5,000-28,000 Lough & Barnes 2000 (Indo-Pacific)

Annelids (HMC) 11,000

2-11,836

Smith et al. 2005 (NZ)

Medernach et al. 2000 (Mediterranean)

Coralline algae In situ incubations

L. corallioides In situ chambers

Maerl (Norway)

Maerl (NW France)

Maerl (W Ireland)

1,500-10,300

300-3,000

895-1,423

876

30-250

Chisholm 2000 (Lizard Is. GBR)

Martin et al 2006

Boscence & Wilson 2003

“

“

Halimeda Standing stock x turnover rate 2,234

1000-3000

Drew 1983

Benthic forams Reef forams

Cold-water forams

2000

480

30-230

0.326

Hallock 1981 (Indo-Pacific)

Yamano et al. 2000 (Green I)

Langer et al. 1997

Wisshak & Ruggeberg 2006 (Baltic)

Bryozoans Pentapora fascialis

“larger bryozoans”

Cellaria sinuosa thickets

358-1,21424-24012-57

Cocito & Ferdeqhini 2001 (NW Med.)

Smith & Nelson 1994

Bader & Schafer 2005 (British Channel)

Echinoderms Ophiothrix fragilis 682 Migne et al. 1998 (Dover Strait)

Molluscs Potamocorbula amurensis (clam)

221 (+/-184) Chauvaud et al. 2003 (San Francisco)

PHOTOTROPHIC

CarboOcean-2006

Recent ‘discoveries’: Rhodoliths / Maerl Beds

Foster 2001

In high latitudes, usually clear water In tropics/ subtropics, where coral reefs are unsuccessful

McCalester

CarboOcean-2006

Bosence & Wilson 2003 (NE Atlantic Maerl Beds)

These production and accumulation rates are similar to the lower end of such rates from tropical coral reef environments. This is achieved by high standing crops that compensate for the lower growth rates of the temperate algae.

Production

g CaCO3 m–2 y–1

Accumulation

(m ky–1)

W Ireland 30-250

NW France 876

Norway 895-1,423

Norway 0.8-1.4

Orkney 0.08

Cornwall 0.5

tropical coralline algae 1,500-10,300

Corals 5,000-28,000 0.12-1.80

CarboOcean-2006

Roberts et al. Science 2006

Recent ‘discoveries’: Cold-water corals(not quite “shelf” deposition)

Challenger Mound:Eos Article, 21 Nov 2006Trevor Williams and 29 others

Mounds:600-900 m depthsUp to 155 m accumulation over 2 MY(10 m per glacial cycle)

CarboOcean-2006


AIM

S


More than Reefs?



CarboOcean-2006

Budget for Reef: Greef + Dreef + T (net Gshelf > Greef)Budget for C-Cycle: Gshelf + Dshelf

G = Community calcification + inorganic cementation

(+)

D = Dissolution

(–)

T = Transport on/off reef

(+ or –; usually –)

Rates vary with T, Ω, Light, …

Export limits reef development without necessarily affecting carbon cycle.

Rates vary with T, Ω, Bioerosion …

Rates vary with framework versus sediments, hydrodynamic regime, shelf morphology, …

CarboOcean-2006

Technique Measures: Timescale

Skeletal incorporation of radioisotopes 45Ca, 14C

Gskel + Dskel Minutes to hours

Buoyant weight Gskel + Dskel Duration of experiment

ΔAlk of monoculture or ΔpH-ΔO2

Gskel + Dskel Discrete measurements over duration of experiment

Coral band increment Gskel + Dskel + Ginorg Integrated over time of band formation + post-depositional cementation

Growth rate x standing stock

Usually generation time/turnover rate of organism

ΔAlk of closed system Gsys + Dsys Discrete measurements over duration of experiment

ΔAlk in open system Gsys + Dsys + mixing Discrete measurements over duration of experiment – requires knowledge of mixing regime

Sedimentological(thickness x density) /time

Gsys + Dsys + transport Months to > millenia

Calcification Measurements(not always the same thing)

Org

anis

ms

& Co

mm

uniti

es

Syst

ems

CarboOcean-2006

Dissolution

Photo/Resp.

InorganicCementation

Net organism calcification

Dissolution

Organic MatterResp.


Bioerosion

Dissolution

Net reef accumulation

CalcificationInputs from

land

export

Exchange with the ocean

Netorganism

calcification

AlkalinityAnomaly

SedimentVolume

CarboOcean-2006

Species Extension ratecm y-1

G*g CaCO3 m-2 y-1

source

F pallida 0.41-0.71(0.57)

5,900-13,200(8,200)

Highsmith 1979

G retiformis 0.49-0.85(0.68)

8,300-14,500(11,600)

Highsmith 1979

P lutea 0.35-1.18(0.76)

4,900-16,600(10,700)

Highsmith 1979

M annularis 0.61-1.44(0.98)

7,700-15,500(12,300)

Dodge & Brass 1984

Porites spp. 0.13-2.21(1.25)

5,100-28,100(16,000)

Lough et al. 1999

P lutea 0.61-1.69(1.09)

6,600-19,600(12,500)

Bessat & Bigues 2001

* G is per surface area of the organism

Coral Calcification(individual species)

CarboOcean-2006

Dissolution

Photo/Resp.



Dissolution

Organic MatterResp.


Bioerosion

Dissolution



land

export


AlkalinityAnomaly

CarboOcean-2006

System Gg CaCO3 m-2 y-1

Source

Mesocosm 5,300 Leclerc et al. 2002

B2 mesocosm 2,700 Langdon et al. 2000

REEFS**Reef flatsAlgal-dominatedSediments

500-12,600-40-4,000

-100-1,200

Reviewed by Gattuso et al. 1998

Halimeda meadows 1,200-3,200 Freile et al. 1993

*G is per surface area of the reef

Coral Community & Reef Calcification

CarboOcean-2006

Growth forms can affect production and accumulation rates per m2

Did the emergence of Acropora accelerate carbonate production?

18,300 g m-2 y-1

7,000 g m-2 y-1

CarboOcean-2006

Model of Reef Growth versus Sea Level Rise

drowned/sediment

massive

branching 1

branching 2

seafloor

120 m

CarboOcean-2006

Dissolution

Photo/Resp.



Dissolution

Organic MatterResp.


Bioerosion

Dissolution



land

export


SedimentVolume

CarboOcean-2006

Location & substrate mmol m-2 night-1 g CaCO3 m-2 y-

1

Source

Hawaiian reef 22% coral cover

17.7 646 Yates & Halley 2003

Hawaiian reef coral rubble

14.1 515 Yates & Halley 2003

Hawaiian reef 10% coral cover

13.0 475 Yates & Halley 2003

Moorea sandy bottom 9.4 343 Boucher et al. 1998

Florida patch reef w 10% coral cover

5.5 201 Yates & Halley 2003

Florida seagrass 4.7 172 Yates & Halley 2003

Hawaiian sand bottom 3.3 120 Yates & Halley 2003

Florida sand bottom 3.0 110 Yates & Halley 2003

Reef coralline algae 2.7 98 Chisholm 2000

Florida patch reef top 1.1 40 Yates & Halley 2003

Dissolution Rates

CarboOcean-2006

Location & substrate Bioerosiong CaCO3 cm-3 y-1

Source

GBR(Porites blocks)

0.043-0.212

MooreaHydrolithon onkodes

0.12 (live)0.49 (dead)

Reunion & Moorea reef flats 0.8 (max) Peyrot-Clausade et al. 2000

French Polynesia lagoons

(Porites lutea blocks)

0.25 (max) Pari et al. 1998

Kenya reefs

(based on echinoid gut contents)

0.120 (unprotected)

0.005 (protected)

0.071 (newly protected)

Carreiro-Silva & McClanahan 2001

Lee Stocking I & One Tree I

(microbial bioerosion only)

0.052 (LSI leeward reef)

0.0001 (LSI 275 m)

0.002 (OTI patch reef)

Vogel et al. 2000

Galápagos

(blocks of P lobata and cathedral limestone)

2.54 (P lobata) 0.26 int + 2.28 ext

0.41 (cathedral ls) 0.06 int + 0.35 ext

Reaka-Kudla et al. 1996

Bioerosion Rates

CarboOcean-2006

Galapagos example

Eucidaris thouarsii

Galápagos Coral ReefsReefs disappeared in <20 years

CarboOcean-2006

Bioerosion- the breakdown of CaCO3 -

1. Bioerosion rates can exceed calcification rates2. Bioerosion creates sediments, includes some

dissolution, and probably enhances dissolution, but … Bioerosion ≠ Carbonate Removal

3. Dead surfaces suffer higher bioerosion rates than live surfaces (most studies done with dead CaCO3 blocks)

4. Types of bioerosion are important:

Main bioeroders: sponges and echinodermsRunners up: fish and boring molluscs

Borers tend to create much finer particles than grazers

CarboOcean-2006

Interpreting Net Accretion Rates from Reef Cores

branchingframework

head coralframework

fore reefdetritus

head coralframeworkback reef

sediments1-2 mm y-1

4-5 mm y-1

6-8 mm y-1

3-10 mm y-1

base rock

coralline algae1-2 mm y-1

8000 YBP

6000 YBP

10m CaCO3

5 mm y-17250 g CaCO3 m-2 y-1

CarboOcean-2006

System g CaCO3 m-2 y-1 Source

Reef accumulation from cores (50% porosity)

1,200-18,0008,400

(modal value)

Hopley & Davies (in press)


7,500 Montaggioni 2005


7,450 Dullo (pers. comm.)

Whole-reef accumulation from seismic data

~9,000 in early Holocene

Ryan et al. 2002

*G is per surface area of the reef

Reef Net Accretion Rates

CarboOcean-2006

Dissolution

Photo/Resp.



Bioerosion

Dissolution

Calcification

export

0.8-1.5 g cm2 y-1

0.1-1.3 g cm2 y-1

0.75-0.90 g cm2 y-1

0.004-0.07 g cm2 y-10.1-0.5 g cm2 y-1

Net communitycalcification

Net reefaccumulation

CarboOcean-2006

A High Preservation Rate?

Reef accumulation rates indicate

1) very little carbonate loss

... OR,

2) today’s calcification rates are lower than in the past

Coral reefs have declined from anthropogenic stress in the last century, but coral reef calcification has probably been declining for thousands of years.

CarboOcean-2006

Changes in Reef CaCO3 Accumulation Over Time(Wistari Reef, Australia)

2

4

6

8

10

10 9 8 7 6 5 4 3 2 1 0

Acc

um. R

ate

g cm

-2 y

-1

103 Years Before Present Ryan et al. 2001

Average Holocene Accumulation

Accumulation History

CarboOcean-2006


NO

AA


More than Reefs?



CarboOcean-2006

Physical Variables that Affect Calcification

TemperatureTemperature Latitude

Saturation StateSaturation State Latitude

IrradianceIrradiance Depth, Latitude

ΩΩTT

CarboOcean-2006

Post-glacial Reef Deposition

9000 ybp8000 ybp7000 ybp

5000 ybp5000 ybp3000 ybp

CarboOcean-2006

Post-glacial Reef DepositionWhat has limited CaCO3 Production/Accumulation?

5000 ybp3000 ybpTR↑

Reef growth progressively limitshydrographic exchange andresidence time increases

CarboOcean-2006

Saturation State Changes with Residence TimeBroecker & Takahashi 1966

Bahamas Bank

CarboOcean-2006

G = ƒ(z,Tr)

Carbonate production is favored at edges of the platform and slows down dramatically beyond 20 m of edge.

Demicco & Hardie, J. Sed Res. 2002

G (kg m-2 y-1)

Tr (days)

0.0

5.5

200

0

Calcification Ratesversus

Residence TimeDemicco & Hardie 2002

CarboOcean-2006

Conclusions 1) Coral reef systems are not big players in the organic component of the C-cycle, but ARE in terms of CaCO3

2) Other shelf ecosystems may be important in accumulation of CaCO3 but their budgets are poorly constrained

3) Coral reef CaCO3 production appears to have declined after sea level stabilized

4) This may be a natural process related to evolution of longer seawater residence times on continental shelves.

1) Coral reef systems are not big players in the organic component of the C-cycle, but ARE in terms of CaCO3




















CarboOcean-2006

END

CarboOcean-2006

CarboOcean-2006

The “Darwin Point”- Clues from High Latitudes -

Clue #1: reef-building at higher latitudes occurs in very clear waters

Clue #2: reef depth shallows at higher latitudes (need diagram)

CarboOcean-2006

The basic calculation:Light-based calcification calculated on an hourly basis for a full year and total calcification over the entire depth of the reef is summed.

CarboOcean-2006

G = Gmax tanh Iz/Ik

Zmax = log(Imin/Isurf) K490

Iz typically 2000Ik 250-300

… light is not limiting at surface

CarboOcean-2006

LightOnly

CarboOcean-2006

LatitudinalEffects

Geq = 2 x G30°

CarboOcean-2006

With Dissolution(net dissolution occurs only

during night time, constant with depth and latitude)

CarboOcean-2006

Latitudinal Effects

+Dissolution

CarboOcean-2006

Temperature Effects on Calcification

Marshall & Clode 2004

Lough & Barnes 2000

CarboOcean-2006

Closed system processes

Typical aquarium (closed) systemcoral (calcifying surface)sediments (mineral composition,

grain size)water volume, well mixed, open to air-

sea gas exchangediurnal light cycle

calcification

(I, CaCO3 saturation state) sediment dissolution

(CaCO3 saturation state) air-sea gas exchange (T, wind

speed, air-sea pCO2 gradient) changes in seawater chemistry are

calculated

CO32–

HCO3–

CaCO3

Ca2+

CO2

CaCO3

CO2

CarboOcean-2006

Closed system results Diurnal cycle of calcification progressively alters seawater chemistry

Dissolution kicks in once saturation state drops below that of high magnesium calcite

Net calcification

System approaches steady state after about 10-20 days

CarboOcean-2006

[CO32] in Biosphere2 Mesocosm

0

100

200

300

400

500

0 20 40 60 80 100

Days

[CO

32-],

m

ol/k

g

system approaches steady state at [CO3

2] 125mol kg-1

C.Langdon, ICRS 2000

CarboOcean-2006

Conflicting Lines of Evidence1) Based on the existing measurements of calcification rates on reefs, and reef

flats, there is little indication that calcification rates at higher latitudes are significantly lower than calcification rates at lower latitudes. (need Gattuso data)

1) Note that most of these measurements are from reef flats or shallower parts of reefs.2) Note also that these measurements were made across different communities

• Based on the few measurements of calcification rates from massive coral skeletons, calcification rates decline significantly with latitude

• Based on data from branching corals, calcification rates do not seem to decline with latitude

• Calcification rates may depend on water flow/residence time of surrounding water;

2) What about dissolution and/or export?• Basically there are no data on whether dissolution rates increase with latitude or

not.• Same for sediment export.


Documents

CarboOcean-2006 Coral Reefs and the Carbon Cycle Joanie Kleypas National Center for Atmospheric Research NOAA Background on Reefs and Carbon More than