The Carbon Cycle

1. Peter Goedert Bot 437 The Carbon Cycle

2. The processes that influence the carbon cycle • Photosynthesis: CO2 is taken in and fixed during the calvin cycle energy (sunlight) + 6CO2 + H2O > C6H12O6 + 6O2 • Respiration: CO2 is released into the atmosphere as a bi-product C6H12O6 (organic matter) + 6O2 > 6CO2 + 6 H2O + energy

3. The Carbon Cycle and Biological Pump • CO2 fixed (Photosynthesis) • products remain surface or sink out • sequestration leads to more CO2 pulled down into surface waters Biological Pump

4. Trends in the atmosphere The Earth’s atmosphere is composed of mostly Oxygen, Nitrogen, and Carbon Dioxide. Some rough estimates of the percentages that make up the atmosphere are as follows: 78% Nitrogen, 21% Oxygen, and .038% Carbon Dioxide. There are recent trends for increased CO2 levels in the atmosphere with recent industry growth leading to increased emissions into the atmosphere.

5. Fluctuations in carbon dioxide throughout the year Northern Hemisphere •summer time = decrease in CO2 •winter increase in CO2 Southern Hemisphere • shows opposite trends WHY??

6. Algae and decreasing CO2 levels • Two ways that algae have contributed to some declines in CO2 despite the overall increasing trend. 1.) Algae produce organic compounds that cannot be oxidized by microbes to release CO2. 2.) Algae generate large amounts of sediment material composed of carbonate minerals

7. Carbon Sequestration The burial of organic carbon and carbonates in the sediment which will remove carbon from the carbon cycle for long periods of time. • organic carbon: degraded slower than it is produced leading to a loss of CO2 , partly because it sinks to the bottom with dead algae away from microbes that decompose it. ((remains in deep anoxic sediments away from the microbes) Examples: scytonemin (cyano, sheaths, UV protection) algaenans (green algae, tough cell wall, cross linked H-C) Cyst walls (dinoflagelates) Acylpolysaccharides (converted by aquatic bacteria, non-decomposable organic carbon originally from algae) * Marine snow: APS combined with other remains helps it sink out and reach sediment * Over time, converted to fossil fuels (temp and microbe conversions)

8. Carbon Sequestration • Calcium Carbonate: many groups of algae use process of calcification -CO2 or HCO3- incorporated into a hard exterior shell Ex: Cyanobacteria (stomatolites) Reds (rhodoliths) Haptophytes (coccoliths) HCO3- + Ca2+ > CaCO3 + CO2 + H2O CO2 used in photosynthesis

9. The changing environment: Problems and Solutions •Human activities increase CO2 in atmosphere may lead to ocean acidification and dissolution of the calcium carbonate exoskeletons (coccoliths) this in turn will decrease the total amount of carbon sequestration (Godol et al. 2009) so much research is directed in this area. • Experiments with iron fertilization in Fe limited areas have proved to increase blooms of algae, hopefully leading to more atmospheric carbon sequestration, but these were only short term experiments land may lead to possible extrapolation. However, to study performed by Blain et al. 2007, looked at natural fertilization In the Antarctic and were able to predict more about long term fertilization. They concluded that iron fertilization could be a key way in the future to lower the atmospheric CO2.

10. Thank You References: Grahm, L., J. Grahm, and L. Wilcox. 2009. Algae second edition. Pearson Education Inc. San Fransisco. Pg. 20-23. Godol, R., K. Aerts, J. Harlay, R. Kaegl, C. Ro, L. Cho and R. Van Grieken. 2009. Organic surface coating on coccolithophores- Emiliania huxleyi: Its determination and implication in the marine carbon cycle. Microchemical Journal. 91:266-278 Stephane, B. et. al. 2007. Effect of natural iron fertilization on carbon sequestration in southern ocean. Nature. 446:1070-1074. Figures taken from: vision learning website: www.visionlearning.com.