Carbon cycle

Biogeochemical cycles
Carbon cycle

1. Biogeochemical Cycles

2. Biogeochemical Cycle Biogeochemical cycle is a pathway by which a chemical substance moves through both biotic ( biosphere ) and abiotic ( lithosphere , atmosphere , and hydrosphere ) compartments of Earth . The term "biogeochemical" tells us that biological, geological and chemical factors are all involved. The circulation of chemical nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, and water etc. through the biological and physical world are known as biogeochemical cycles. In effect, the element is recycled, although in some cycles there may be places (called reservoirs ) where the element is accumulated or held for a long period of time (such as an ocean or lake for water).

3. Carbon Cycle

4. How are humans affecting the carbon cycle?

5. How are humans affecting the carbon cycle? By cutting down trees and clearing vegetation that naturally absorbs CO 2 Burning fossil fuels (especially coal) releases their stored carbon into the atmosphere Clearing vegetation faster than it is replaced.

6. Effects of disrupting the carbon cycle Global Warming – more CO 2 in the atmosphere will lead to a stronger greenhouse effect Acidification of the oceans – more dissolved CO 2 in the water creates more carbonic acid

7. The first step of the carbon cycle in which the photoautotrophs such as cyanbacteria , green plants, algae, and green and purple sulphur bacteria fix carbon dioxide into organic matter using energy from sunlight. Chemoautotrophs such as Thiobacillus and Beggiatoa also fix carbon dioxide into organic matter, while metabolizing compounds such as hydrogen sulfide for energy.

8. In the next step, chemoheterotrophs such as animals and protozoa eat autotrophs and may in turn be eaten by other animals. Thus as the organic compounds of the autotrophs are digested and resynthesized , the carbon atoms of carbon dioxide are transformed from organism to organism up the food chain.

9. The Carbon Cycle The development of photosynthesis allowed microbes to tap into sunlight energy and provided a mechanism for the first carbon cycle.

10. Where is carbon stored?

11. Where is carbon stored? Air – 0.037% is CO 2 Vegetation – during photosynthesis, plants convert CO 2 into C 6 H 12 O 6 (glucose) Fossil fuels – plant matter that’s been subjected to heat and pressure Ocean – dissolves CO 2 Marine organisms – used to make shells Rocks – limestone is primarily CaCO 3

12. Natural Sources of Carbon Sources of Carbon from Human Activity Death of plants and animals Animal waste Atmospheric CO2 Weathering Methane gas from cows (and other ruminants) Aerobic respiration from terrestrial and aquatic life Burning wood or forests Cars, trucks, planes Burning fossil fuels such as coal, oil and natural gas to produce heat and energy.

13. Natural sources of CO 2 respiration ocean degassing terrestrial degassing wildfires Anthropogenic sources of CO 2 fossil fuel combustion cement production land use changes Natural sinks for CO 2 terrestrial uptake by plants uptake by soils oceanic partitioning biomass production Anthropogenic sinks for CO 2 chemical production biological materials Natural and anthropogenic CO 2 sources and sinks

14. Fossil Fuels

15. White Cliffs of Dover

16. Carbon Reservoir Metric tons carbon Actively cycled Atmosphere CO 2 Ocean Biomass Carbonates Dissolved and particulate organics Land Biota Humus Fossil fuel Earth’s crust 6.7 x 10 11 4.0 x 10 9 3.8 x 10 13 2.1 x 10 12 5.0 x 10 11 1.2 x 10 12 1.0 x 10 13 1.2 x 10 17 Yes Yes No Yes Yes Yes Yes No Global Carbon Reservoirs

17. The carbon cycle is a good example of one that is undergoing a major perturbation due to human activity. Human activity has had a large impact on the atmospheric CO 2 reservoir beginning with industrialization. As a result, the level of CO 2 in the atmosphere has increased 28% in the past 150 years. Carbon source metric tons carbon/ yr Release by fossil-fuel combustion 7 x 10 9 Land clearing 3 x 10 9 Forest harvest and decay 6 x 10 9 Forest regrowth -4 x 10 9 Net uptake by oceans -3 x 10 9 Annual flux 9 x 10 9

18. Natural sources of CO 2 respiration ocean degassing terrestrial degassing wildfires Anthropogenic sources of CO 2 fossil fuel combustion cement production land use changes Natural sinks for CO 2 terrestrial uptake by plants uptake by soils oceanic partitioning biomass production Anthropogenic sinks for CO 2 chemical production biological materials Natural and anthropogenic CO 2 sources and sinks

19. The term reservoir can be used on a global scale or on a smaller scale such as a habitat. What are the major carbon inputs into the environment? plant materials (through photosynthesis) cellulose 15 – 60% hemicellulose 10-30% lignin 5- 30% protein/nucleic acids 2-15% fungal cell walls/arthropods chitin Carbon cycling on the habitat scale The most complex organic polymer found in the environment is humus .

20. Methane generation The methanogens are a group of obligately anaerobic Archaea that can reduce CO 2 to methane (use CO 2 as a terminal electron acceptor) both chemoautotrophically or heterotrophically using small MW molecules such as methanol or acetate. 4H 2 + CO 2 CH 4 + 2H 2 O G = -130.7 kJ Although much methane is microbially produced, there are other sources as well. Methane is a greenhouse gas, 22 times more effective than CO 2 in trapping heat. Methane utilization In most environments, the methane produced is utilized by methanotrophic microbes as a source of carbon and energy. The first enzyme in the biodegradation pathway of methane is methane monooxygenase (MMO).

21. Carbon Cycle Anaerobic Aerobic Carbon Fixation Carbon Fixation CO 2 Respiration And Fermentation Organic Matter CH 2 O Respiration CO 2 Methane Oxidation Methanogenesis H 2 CH 4

22. MARINE CARBON CYCLE

23. Carbon in Oceans Additional carbon is stored in the ocean. Many animals pull carbon from water to use in shells, etc. Animals die and carbon substances are deposited at the bottom of the ocean. Oceans contain earth ’ s largest store of carbon.

24. TERRESTRIAL CARBON CYCLE

25. More notes on Carbon Cycle

26. Carbon Cycle Carbon moves from the atmosphere to plants. In the atmosphere, carbon is attached to oxygen in a gas called carbon dioxide (CO 2 ). With the help of the Sun, through the process of photosynthesis, carbon dioxide is pulled from the air to make plant food from carbon. Carbon moves from plants to animals. Through food chains, the carbon that is in plants moves to the animals that eat them. Animals that eat other animals get the carbon from their food too.

27. Carbon Cycle Carbon moves from plants and animals to the ground. When plants and animals die, their bodies, wood and leaves decay bringing the carbon into the ground. Some become buried miles underground and will become fossil fuels in millions and millions of years. Carbon moves from living things to the atmosphere. Each time you exhale, you are releasing carbon dioxide gas (CO 2 ) into the atmosphere. Animals and plants get rid of carbon dioxide gas through a process called respiration.

28. Carbon Cycle Carbon moves from fossil fuels to the atmosphere when fuels are burned. When humans burn fossil fuels to power factories, power plants, cars and trucks, most of the carbon quickly enters the atmosphere as carbon dioxide gas. Each year, five and a half billion tons of carbon is released by burning fossil fuels. Of the huge amount of carbon that is released from fuels, 3.3 billion tons enters the atmosphere and most of the rest becomes dissolved in seawater . Carbon moves from the atmosphere to the oceans. The oceans, and other bodies of water, soak up some carbon from the atmosphere.