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• The Carbon Cycle
• - Step 1
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• - For Your Consideration
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Lessons > The Carbon Cycle > For Your Consideration

You should now have some understanding of how carbon moves through the system, but you may be wondering about the mechanisms behind this flow. As you read through the following explanations, refer to your Data Table for Lesson 1 Step 2.

Atmosphere: combustion of carbon-based fuel combines carbon, C, and oxygen, O₂, adding CO₂ to the atmosphere. CO₂ is not a by-product of fossil fuel use; it's the direct product of the very reaction that releases the energy.

Biosphere (Terrestrial Plants and Soil): plants (biomass) inhale CO₂ and exhale O₂. When there's more CO₂ available, biomass tends to breathe in more, and therefore grow more. Most scientists now believe that plants have a limited ability to increase their growth rate. (See the Unit 12 video.)

Surface ocean: The amount of gas dissolved in any liquid is proportional to the partial pressure of that gas in the vapor phase above the liquid (Henry's Law). As a result, if we increase the partial pressure of atmospheric CO₂ (i.e. increase the concentration of CO₂), then we force more CO₂ gas to dissolve into the liquid. (In this case, the liquid is the ocean.) In addition to the CO₂ dissolving into the liquid as a gas, CO₂ reacts with H₂O and forms bicarbonate ions (HCO₃^-) and carbonate ions (CO₃^--). This combustion of fossil fuels results in an increase in dissolved surface ocean carbon and a decrease in pH.

Deep ocean: Ocean chemistry involving mineral precipitation, and biological activity, and ocean currents transport the carbon from the surface ocean to the deep ocean over long time-scales.

Thinking Ahead

1. How will the increase in biosphere production of carbon alter the carbon levels in:
   1. Atmosphere
   2. Surface ocean
   3. Deep ocean
   4. Fossil fuels
   5. Number and variety of terrestrial plants and animals?
2. How will the increased carbon levels as noted in your Data Table affect current taxonomy? Will the number and variety of species change? How will they change?
3. From your collected data and what you have learned so far, what do you propose as a solution to this dilemma?