Carbon Cycle

Biogeochemical cycles: The movements of matter within and between ecosystems involving cycles of biological, geological, and chemical processes

Reservoirs: The components of the biogeochemical cycle that contain the matter, including air, water, and organisms.

To keep track of the movement of matter in biogeochemical cycles, we refer to the reservoirs.

Reservoirs can serve as a “source” of the element when atoms and molecules leave a reservoir and as a “sink” when atoms and molecules get stored in the reservoir.

Carbon is the most important element in living organisms; it makes up about 20% of their total body weight. Carbon is the basis of long chains of organic molecules that form the membranes and walls of cells and store energy for later use.

Carbon cycle: the movement of carbon around the biosphere among reservoir sources and sinks

7 Processes that drive the carbon cycle: photosynthesis, respiration, exchange, sedimentation, burial, extraction, and combustion.

Fast part of cycle involves processes that are associated with living organisms that hold carbon for a short period of time. Also includes the exchange of CO2 between the air and water and the combustion of organic carbon which releases CO2 into the atmosphere

Slow part of cycles involves carbon that is held in rocks in soils, or as petroleum hydrocarbons

When plants and algae use photosynthesis, they use solar energy to convert carbon dioxide and water into glucose and oxygen. A portion of this energy is consumed by herbivores and eventually by predators of those herbivores

Those organisms return a portion of their carbon as CO2 when they use aerobic respiration (the process by which cells convert glucose and oxygen into energy, carbon dioxide, and water). Additional carbon is returned after organisms die. Decomposers break down the dead material which returns CO2 to the water or air via respiration

Carbon is exchanged between the atmosphere and the ocean. The amount of carbon released from the ocean into the atmosphere equals the amount of CO2 that diffuses into ocean water. Some of the CO2 dissolved in the ocean enters the food web via photosynthesis and algae

Another portion of the Co2 dissolved in the ocean combines with calcium ions in the water to form calcium carbonate (a compound that can precipitate out of the water and form limestone and dolomite rock via sedimentation and burial)

A small portion of the organic carbon in the dead biomass reservoir is buried. This organic matter becomes fossilized and some of it may be transferred into fossil fuels.

Steady state: when a system’s input equal outputs, so the system isn’t changing over time

Extraction of fossil fuels is the subsequent step of combustion. Combustion of fossil fuels release carbon into the atmosphere as Co2 or into the soil as ash.

Carbon taken up by photosynthesis ends up in the soil. Decomposers in the soil gradually release it at the same rate it is added. The gradual movement of carbon into buried or fossil fuel reservoirs is offset by the slow process that release it.

Combustion of CO2 is leading to warming of the planet. When light energy from the sun hits the Earth’s surface, the energy is absorbed and a portion is emitted as heat. Some of the gases in the Earth’s atmosphere absorb the heat. The gases reemit the head in all directions, causing the planet to become warmer. The gas that contributes most to warming is Carbon dioxide.

Humans have been moving fossilized carbon into the atmosphere at a faster rate than carbon leaves the atmosphere through the processes of sedimentation and burial. Atmospheric carbon has increased due to this reason.

Tree harvesting: trees store a large amount of carbon in their wood. The destruction of forests by cutting and burning increases the amount of CO2 into the air.

What is calcium carbonate (CaCO₃), how is it formed, and how is it involved in the carbon cycle? It removes CO₂ from ocean, and as these organisms die, their skeletons and shell will fall to the bottom of the ocean where over time they will become rocks or fossil fuels.