Coral Reefs and the Carbon Cycle

1
Coral Reefsand the Carbon Cycle
NOAA
Background on Reefs and Carbon More than
Reefs? Reef CaCO3 Production Accumulation Contro
ls on Reef Calcification
Joanie Kleypas National Center for
Atmospheric Research
2
Coral Reefsand the Carbon Cycle
NOAA
Background on Reefs and Carbon More than
Reefs? Reef CaCO3 Production Accumulation Contro
ls on Reef Calcification
3
Coral Reefs- Organic Carbon Production -

• Organic Carbon Production in Low Nutrient Waters
• High organic production (79584 g C m2 y1)
• Topographically induced upwelling, internal tidal
  bores endo-upwelling
• Efficient production of organic carbon (Nitrogen
  fixation)
• C N P
• Coral reefs 550301
• Open ocean 106161

Smith, 1988
4
Coral Reefs- Organic Carbon Production
-(Gattuso, Frankignoulle, Wollast 1998)
Pg/R Reef Flats 1.07
0.1 (n43) Reef System 1.28 0.2 (n9)
Respiration
Gross Production
Organic C metabolism of coral reefs is
balanced or slightly autotrophic
5
Coastal Ecosystems - Organic Carbon Production
-(Gattuso, Frankignoulle, Wollast 1998)
Gross Prod. mol C m2 y1 Area 106 km2 NEP Tmol C y1
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
6
Coastal Ecosystems - Organic Carbon Production
-(Gattuso, Frankignoulle, Wollast 1998)
Gross Prod. mol C m2 y1 Area 106 km2 NEP Tmol C y1
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
7
Coral Reefs - Inorganic Carbon Production -
(Milliman 1993 Milliman Droxler 1996)
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
3 shelves open ocean 290.0 20 60 11
8
Coral ReefHypothesis
Changes in basin-shelf partitioning of CaCO3
production caused glacial-interglacial
fluctuations in atmospheric CO2
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
9
Estimates of Shelf CaCO3 Flux
Flux 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
10
600,000 km2
Smiths (1978) reef area estimate

• Smith Kinseys (1976) avg calcn rate
• 20 reefs _at_ 4000 g m-2 y-1
• 80 lagoons _at_ 800 g m-2 y-1

1500 g m-2 y-1
0.9 x 109 tons CaCO3 y-1
Net CaCO3 production
10 dissolved/exported 10 biological
erosion/corrosion
20
0.7 x 109 tons CaCO3 y-1
Net CaCO3 accumulation
11
Coral Reefsand the Carbon Cycle
NOAA
Background on Reefs and Carbon More than
Reefs? CaCO3 Production Accumulation Controls
on Reef Calcification
12
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

cold water corals may cover as large an area
as warm-water corals that form shallow reefs
(Williams et al., Eos 21 Nov 2006)
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)
13
How Good are Estimates of Shelf Accumulation?

• What about non-tropical carbonates?
• Milliman Droxler 1996 estimated that for
  non-tropical shelves
• calcification rates lt 20 of tropical carbonates
• net accumulation 30 of tropical
  carbonates

These data are even less constrained than for
reefs
14
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 algae Coralline red
algae Green algae Halimeda/Penicillus Forams Spong
es Bryozoans Brachiopods Molluscs Annelids Echinod
erms Arthropods
15
Calcification Rates of Benthic Calcifiers
Calcifier 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 358-1,214 24-240 12-57 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
16
Recent discoveries Rhodoliths / Maerl Beds
In high latitudes, usually clear water In
tropics/ subtropics, where coral reefs are
unsuccessful
McCalester
Foster 2001
17
Bosence Wilson 2003 (NE Atlantic Maerl Beds)
Production g CaCO3 m2 y1 Accumulation (m ky1)
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

• 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.

18
Recent discoveries Cold-water corals(not
quite shelf deposition)
Challenger Mound Eos Article, 21 Nov 2006 Trevor
Williams and 29 others Mounds 600-900 m
depths Up to 155 m accumulation over 2 MY (10 m
per glacial cycle)
Roberts et al. Science 2006
19
Coral Reefsand the Carbon Cycle
AIMS
Background on Reefs and Carbon More than
Reefs? Reef CaCO3 Production Accumulation Contro
ls on Reef Calcification
20
Budget for Reef Greef Dreef T (net Gshelf
gt 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, O, Light,
Rates vary with T, O, Bioerosion
Rates vary with framework versus sediments,
hydrodynamic regime, shelf morphology,
Export limits reef development without
necessarily affecting carbon cycle.
21
Calcification Measurements(not always the same
thing)
Technique Measures Timescale
Skeletal incorporation of radioisotopes 45Ca, 14C Gskel Dskel Minutes to hours
Buoyant weight Gskel Dskel Duration of experiment
?Alk of monoculture or ?pH-?O2 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
?Alk of closed system Gsys Dsys Discrete measurements over duration of experiment
?Alk 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 gt millenia
Organisms Communities
Systems
22
Alkalinity Anomaly
Net organism calcification
Net organism calcification
Photo/Resp.
Calcification
Exchange with the ocean
Inputs from land
Inorganic Cementation
Dissolution
Sediment Volume
Organic Matter Resp.
Net reef accumulation
?
Inorganic Cementation
Dissolution
Dissolution
Bioerosion
export
23
Coral Calcification(individual species)
Species Extension rate cm 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
24
Alkalinity Anomaly
Net organism calcification
Photo/Resp.
Calcification
Exchange with the ocean
Inputs from land
Inorganic Cementation
Dissolution
Organic Matter Resp.
Net reef accumulation
?
Inorganic Cementation
Dissolution
Dissolution
Bioerosion
export
25
Coral Community Reef Calcification
System G g CaCO3 m-2 y-1 Source
Mesocosm 5,300 Leclerc et al. 2002
B2 mesocosm 2,700 Langdon et al. 2000
REEFS Reef flats Algal-dominated Sediments 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
26
Growth forms can affect production and
accumulation rates per m2
7,000 g m-2 y-1
Did the emergence of Acropora accelerate
carbonate production?
18,300 g m-2 y-1
27
Model of Reef Growth versus Sea Level Rise
drowned/ sediment
massive
branching 1
branching 2
120 m
seafloor
28
Net organism calcification
Photo/Resp.
Calcification
Exchange with the ocean
Inputs from land
Inorganic Cementation
Dissolution
Sediment Volume
Organic Matter Resp.
Net reef accumulation
?
Inorganic Cementation
Dissolution
Dissolution
Bioerosion
export
29
Dissolution Rates
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
30
Bioerosion Rates
Location substrate Bioerosion g CaCO3 cm-3 y-1 Source
GBR (Porites blocks) 0.043-0.212
Moorea Hydrolithon 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
31
Galápagos Coral ReefsReefs disappeared in lt20
years

• Galapagos example

Eucidaris thouarsii
32
Bioerosion- the breakdown of CaCO3 -

• Bioerosion rates can exceed calcification rates
• Bioerosion creates sediments, includes some
  dissolution, and probably enhances dissolution,
  but Bioerosion ? Carbonate Removal
• Dead surfaces suffer higher bioerosion rates than
  live surfaces (most studies done with dead CaCO3
  blocks)
• Types of bioerosion are important
• Main bioeroders sponges and echinoderms
• Runners up fish and boring molluscs
• Borers tend to create much finer particles than
  grazers

33
Interpreting Net Accretion Rates from Reef Cores
6000 YBP
4-5 mm y-1
coralline algae 1-2 mm y-1
head coral framework
back reef sediments
6-8 mm y-1
1-2 mm y-1
branching framework
10m CaCO3 5 mm y-1
7250 g CaCO3 m-2 y-1
3-10 mm y-1
head coral framework
fore reef detritus
base rock
8000 YBP
34
Reef Net Accretion Rates
System g CaCO3 m-2 y-1 Source
Reef accumulation from cores (50 porosity) 1,200-18,000 8,400 (modal value) Hopley Davies (in press)
Reef accumulation from cores (50 porosity) 7,500 Montaggioni 2005
Reef accumulation from cores (50 porosity) 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
35
Photo/Resp.
Net organism calcification
0.8-1.5 g cm2 y-1
Calcification
Inorganic Cementation
Dissolution
Net community calcification
0.1-1.3 g cm2 y-1
Net reef accumulation
0.75-0.90 g cm2 y-1
Bioerosion
0.1-0.5 g cm2 y-1
0.004-0.07 g cm2 y-1
Dissolution
export
36
A High Preservation Rate?

• Reef accumulation rates indicate
• very little carbonate loss
• ... OR,
• todays 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.

37
Changes in Reef CaCO3 Accumulation Over
Time(Wistari Reef, Australia)
Average Holocene Accumulation
2 4 6 8 10
Accum. Rate g cm-2 y-1
Accumulation History
10 9 8 7 6 5 4
3 2 1 0
103 Years Before Present
Ryan et al. 2001
38
Coral Reefsand the Carbon Cycle
NOAA
Background on Reefs and Carbon More than
Reefs? Reef CaCO3 Production Accumulation Contro
ls on Reef Calcification
39
Physical Variables that Affect Calcification

• Temperature Latitude
• Saturation State Latitude
• Irradiance Depth, Latitude

T
O
40
Post-glacial Reef Deposition
5000 ybp
5000 ybp
3000 ybp
7000 ybp
8000 ybp
9000 ybp
41
Post-glacial Reef DepositionWhat has limited
CaCO3 Production/Accumulation?
5000 ybp
3000 ybp
TR?
Reef growth progressively limits hydrographic
exchange and residence time increases
42
Saturation State Changes with Residence
TimeBroecker Takahashi 1966
Bahamas Bank
43
G (kg m-2 y-1)
5.5
Calcification Rates versus Residence Time Demicco
Hardie 2002
0.0
G ƒ(z,Tr) Carbonate production is favored at
edges of the platform and slows down dramatically
beyond 20 m of edge.
200
Tr (days)
0
Demicco Hardie, J. Sed Res. 2002
44
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
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
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
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
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
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.

45
END
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47
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)

48
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.
49
Zmax log(Imin/Isurf) K490
G Gmax tanh Iz/Ik
Iz typically 2000 Ik 250-300 light is not
limiting at surface
50
LightOnly
51
LatitudinalEffectsGeq 2 x G30
52
With Dissolution(net dissolution occurs only
during night time, constant with depth and
latitude)
53
Latitudinal EffectsDissolution
54
Temperature Effects on Calcification
Lough Barnes 2000
Marshall Clode 2004
55
Closed system processes

• Typical aquarium (closed) system
• coral (calcifying surface)
• sediments (mineral composition, grain size)
• water volume, well mixed, open to air-sea gas
  exchange
• diurnal 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

CO2
CO2
HCO3
CO32
Ca2
CaCO3
CaCO3
56
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
57
CO32? in Biosphere2 Mesocosm
system approaches steady state at CO32? ?
125?mol kg-1
C.Langdon, ICRS 2000
58
Conflicting Lines of Evidence

• 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)
• Note that most of these measurements are from
  reef flats or shallower parts of reefs.
• 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.

Net organism calcification