The ocean's carbon cycle is a vital process involving the exchange of carbon between the atmosphere, ocean surface, marine organisms, and deep ocean waters.
Carbon Exchange at the Ocean's Surface
The surface of the ocean acts as a significant interface for carbon exchange.
- Gas Exchange: The ocean surface constantly exchanges gases with the atmosphere. This includes the absorption of carbon dioxide (CO2) from the air and the release of other gases, as stated in our reference which notes, "Surface waters exchange gases with the atmosphere, absorbing and releasing carbon dioxide, oxygen, and other gases."
- CO2 Absorption: When atmospheric CO2 levels are high, the ocean absorbs a considerable amount of it, acting as a crucial carbon sink. Conversely, when atmospheric levels are low, the ocean can release CO2 back into the air.
The Role of Phytoplankton
Phytoplankton play a crucial role in the oceanic carbon cycle.
- Photosynthesis: These microscopic, plant-like organisms use photosynthesis to convert CO2 into organic sugars, providing the foundation of the marine food web. Our reference highlights this process: "Plant-like phytoplankton living in the ocean convert carbon dioxide into sugars that feed marine ecosystems."
- Carbon Fixation: Phytoplankton effectively remove CO2 from the water, converting it into organic carbon, which is then consumed by other marine organisms. This process is known as carbon fixation.
The Biological Pump
The term "biological pump" describes the process where carbon is transferred from the surface waters to the deep ocean.
- Organic Matter Sinking: When phytoplankton and other marine organisms die, their remains sink into the deeper ocean. This organic matter carries the carbon with it.
- Decomposition: In the deep ocean, this organic matter is decomposed by bacteria and other organisms, some of which release carbon back into the water, while other carbon may be buried in sediments.
- Long-Term Storage: A portion of this sinking carbon is sequestered in the deep ocean for long periods, helping to regulate atmospheric CO2 levels.
Summary of the Oceanic Carbon Cycle
| Process | Description | Location |
|---|---|---|
| Gas Exchange | Absorption and release of CO2 and other gases between the ocean surface and the atmosphere. | Ocean surface |
| Photosynthesis | Phytoplankton convert CO2 into sugars. | Ocean surface |
| Biological Pump | Transfer of organic carbon from the surface to the deep ocean through sinking and decomposition of organisms. | Ocean surface to deep ocean |
| Carbon Storage | Long-term sequestration of carbon in deep ocean waters and sediments. | Deep ocean, sediments |
