Here on land much of our electricity is generated through the burning of fossil fuels. These fossil fuels release large amounts of carbon into the atmosphere. This carbon is sometimes absorbed by plant life on land, but much of it passes over the 71% of the Earth’s surface covered by oceans, and is absorbed into the water beginning the carbon cycle.
This carbon is then absorbed by phytoplankton, microscopic organisms in the ocean that photosynthesize to produce their energy (note this role can also be filled by macroscopic species of seaweed). The more carbon dioxide is put into the atmosphere, the faster phytoplankton can multiply thus draining the ocean of carbon dioxide faster. To achieve equilibrium the oceans suck carbon dioxide out of the atmosphere even faster, thus combating the rising levels of carbon dioxide in both our atmosphere and in the ocean itself. If we are unable to achieve this equilibrium, the ocean will become saturated with carbon, which can lead to the acidification of the water. Acidification in turn can make it harder for both microscopic and macroscopic organisms to use calcium in the water to create their shells. Photosynthesizing creatures, like phytoplankton, are one of the only forces which can counteract this progress, and by increasing their biomass, slow or reverse the course of ocean acidification.
At the next step of the carbon cycle, krill, zooplankton, and jellyfish then eat these phytoplankton. When these animals breathe they can release the carbon back into the ocean, which can exchange this carbon with the atmosphere, this completes the carbon cycle. Most of the carbon in an organism is the material that makes up its body, when creatures die, their bodies begin to fall to the bottom of the ocean as marine snow.
Most of this marine snow is eaten by fish and other animals living in the Twilight Zone of the ocean. At night, these animals migrate up to the surface of the ocean and release the carbon as they defecate and respire, this keeps more carbon up near the surface of the ocean allowing the phytoplankton to continue absorbing it.
During the day, whales come down from the surface to hunt the larger squid in the deep that are often apex predators in their environment. After killing and eating these squid, the whales return to the surface where they defecate, returning the carbon to the phytoplankton, while also exhaling the carbon directly into the atmosphere.
When large creatures such as whales die, most of their bodies sink to the ocean floor. These massive amounts of food, when they reach the abyssal plain, are called ‘whale drops’. These whale drops attract lots of deep sea scavengers, from crabs, to giant isopods, to snail fish, hagfish, and greenland sharks.
Bottom dwellers in the ocean eat much of the carbon that falls to the surface, and they in turn are eaten by predatory squid and fish that return to the Twilight Zone and from there up to the surface where they can release the carbon, but most carbon that reaches the ocean floor doesn’t come up this way. It stays on the ocean floor, often for centuries, until ocean currents push it to a spot where deep water rises and becomes surface water. One of these areas is in the Indian Ocean, another is in the North Pacific. In these zones, the cold water being pulled up to the surface carries with it much of the nutrients and carbon that had been trapped for centuries.
But even with the fish pump, the whale pump, and the natural ocean currents, much of the carbon that reaches the ocean floor gets buried under successive layers. Some of this carbon becomes the fossil fuels we drill for today, much of it becomes limestone. The Oceans are called a ‘Carbon Sink’ for a reason, once carbon goes in, it can take a long time to get it back out. But by growing more sargasso seaweed, and increasing marine life through Seasteading, we can allow the carbon cycle to run faster, and help regulate the Earth’s carbon dioxide content better.