Blue Carbon: Ocean Carbon Sequestration Quiz

The biological pump starts with phytoplankton taking in CO2. When these organisms and the animals that eat them die or produce waste, the carbon sinks to the deep ocean, effectively "pumping" it away from the atmosphere.

This is known as the solubility pump. This is why the cold polar oceans are incredibly important for carbon sequestration; they act like a giant sponge, soaking up CO2 from the air and sinking it as the water becomes dense.

Blue carbon refers to the carbon captured by the worlds ocean and coastal ecosystems. These habitats can store up to ten times more carbon per acre than tropical forests.

Living things are the main drivers of sequestration. Corals use carbon to build skeletons, and even a single whale carcass carries a massive amount of carbon to the seafloor where it can be stored for centuries.

Once carbon reaches the deep ocean, it can stay there for hundreds or thousands of years. Eventually, it may be buried in the mud and turn into sedimentary rocks like limestone.

As the ocean absorbs more CO2, it becomes more acidic. This acidity makes it harder for organisms like clams, oysters, and corals to build their shells, which actually reduces the oceans ability to store carbon in the form of calcium carbonate.

Marine snow consists of organic bits, waste, and tiny shells that drift down from the surface. It is a vital link in the biological pump, feeding deep-sea life and burying carbon.

The surface ocean is in constant "conversation" with the air, swapping CO2 back and forth. The deep ocean is isolated, meaning once carbon gets down there, it is "locked away" from the climate for a very long time.

In parts of the ocean that lack nutrients, adding small amounts of iron can cause a massive growth of phytoplankton. Some scientists have proposed "iron fertilization" as a way to increase carbon sequestration, though it is controversial.

The global conveyor belt (thermohaline circulation) moves CO2-rich surface water to the deep sea. If this circulation slows, the "solubility pump" becomes less efficient at moving carbon into long-term storage.

Calcifiers like coccolithophores play a double role. While they store carbon in their shells, the chemical process of making the shell actually releases some CO2 back into the water.

Warm water holds less gas, meaning it can "leak" CO2 back into the air. Destroying mangroves and losing large animals (which store carbon in their bodies) both reduce the ocean's sequestration potential.

The physical pump relies on ocean circulation. Cold, CO2-heavy water sinks at the poles, carrying the gas down with it, while upwelling currents eventually bring it back up elsewhere.

Fast-growing seaweeds like kelp can absorb large amounts of carbon. If the kelp is harvested or sinks to the deep sea, that carbon is removed from the atmosphere.

Currently, the ocean absorbs about 25 to 30 percent of the CO2 humans put into the air. If it ever becomes a "source" instead of a "sink," global warming would accelerate significantly.