1. Algae and the Calcium Carbonate Cycle
Natalie Lee

2. Atmosphere CO2 Ocean HCO3- Marine CaCO3 organisms Marine
Atmospheric exchange
Ocean HCO3-
Calcification
Marine CaCO3
organisms
Sinking/Sedimentation
Marine
sediments CaCO3

3. Acidification of water forms carbonic acid, H2CO3, which dissolves CaCO3
Lysocline = distinct increase in dissolution rate
Carbonate Compensation Depth (CCD) = equilibrium between precipitation and dissolution of CaCO3
Ca2+ lost to sedimentation is recycled by rock weathering

4. BICARBONATE UTILIZATION CO2 + 2H2O + >8 photons  CH2O + H2O + O2
CO2 + Ca2+ + H2O  CaCO3 + 2H+
CALCIFICATION
2H+ + 2HCO3-  2CO2 + 2H2O
BICARBONATE UTILIZATION
CO2 + 2H2O + >8 photons  CH2O + H2O + O2
PHOTOSYNTHESIS
2HCO3- + Ca2+  CaCO3 + H2O + CO2
NET

5. Calcification Ca2+ transport across membrane coupled with H+ export
H+ reacts with HCO3- in water to form CO2
CO2 used in photosynthesis and binds with Ca2+ to form CaCO3
Calcification is an adaptation that allows algae to obtain sufficient inorganic carbon for photosynthesis

6. Calcareous Algae Cyanobacteria Green algae Brown algae Red algae
Coccolithophores Halimeda
Discosphaera tubifera
Pneophyllum conicum

7. Focus On: Distribution of Crustose Coralline Algae Fabricius & De’ath, 2001
Observational study of 144 reef sites at Great Barrier Reef
Which factors correlate with CCA percent cover?
Thickness of sediment deposits
Visibility
Reef slope angle
Distances across and along shelf

8. Focus On: Distribution of Crustose Coralline Algae Fabricius & De’ath, 2001

9. Focus On: Distribution of Crustose Coralline Algae
Fabricius & De’ath, 2001
CCA cover has strong inverse relationship with cross-shelf distance and with sediment deposit
CCA cover has weak relationship with visibility and with slope
All variables strongly related to cross-shelf distance, therefore it is the single variable that best explains variability in CCA cover

10. Focus On: Calcification in Coccolithophores Satoh et al., 2009
What factors induce calcification in Emiliania huxleyi?
Cold stress
Phosphate deprivation
Temperature decrease from 20°C to 12°C suppressed growth, caused Pi depletion and increase in alkaline phosphatase activity, and increase in coccolith production
Important to our understanding of the relationship between phosphate availability and temperature to oceanic carbon flux.

11. References
Fabricius, K., and G. De’ath. (2001). Environmental factors associated with the distribution of crustose coralline algae on the Great Barrier Reef. Coral Reefs 19:303–309.
Graham, L. E., J. M. Graham, and L. W. Wilcox. (2009). Algae (2nd ed.). San Francisco: Pearson Benjamin Cummings.
Ridgwell, A., and R. E. Zeebe. (2005). The role of the global carbonate cycle in the regulation and evolution of the Earth system. Earth and Planetary Science Letters 234:
Satoh, M., K. Iwamoto, I. Suzuki, Y. Shiraiwa. (2009). Cold stress stimulates intracellular calcification by the Coccolithophore, Emiliania huxleyi (Haptophyceae) under phosphate-deficient conditions. Marine Biotechnology 11:
“The Marine Carbon Cycle.”