Ocean guardians: the gigantic carbon cycle between cetaceans, plankton, and the seafloor

A tree, the system that par excellence, in our imagination, fixes carbon dioxide, absorbs less than 50 kilograms per year. According to the International Monetary Fund, whales are the most complex technologies we can find to capture carbon from the air and neutralize it in the accounting of greenhouse gases. When an animal of this size dies, its body sinks, plunges to the ocean floor, and here its decomposition ends; it returns "to the earth", back to rock and dust. Here it buries the carbon, which is forgotten by the world.

But whales are part of a trophic network: they feed and in turn provide nourishment. Plankton feeds them, helps them grow, and contributes to the process by which their bodies become guardians and protectors of this substance, carbon, precious and dangerous. In turn, these giants of the oceans fertilize the waters with fluids and excrement, rich in nitrogen and iron, which are dispersed and distributed through dives and migrations, and promote the growth of phytoplankton, a producer of oxygen and a sequester of carbon dioxide.

 An increase in the number of whales and, consequently—or as a consequence of—an increase in the amount of phytoplankton would contribute to a far greater sequestration of CO₂. Fertilizer is not produced only by these large cetaceans, however, but by all marine animals—bluefin tuna, rays, sharks—which at the same time exert pressure on the numbers of the marine "herbivores" such as turtles and dugongs that, if they grew too numerous, would risk compromising the meadows responsible for producing oxygen—thus being fundamental in the process of climate regulation. Today, the amount of CO₂ sequestered by plankton is 37 billion cubic meters per year, the equivalent of four Amazon rainforests.

In the same way, it is plankton that stores CO₂ and removes it from the world: the golden boxes of diatoms represent an important container of carbon dioxide and when they die they sink toward the bottom, become sediments, and part of this molecule remains there. 

1. At least until the seabed is extracted through activities such as deep sea mining, the practice of extracting parts of the earth in the depths of the oceans where there are believed to be valuable minerals for technological development and, in particular, the ecological transition. 
2. Or until it is disturbed: bottom trawling nets are a fishing device that drags along the surface of the seabed, carrying away whatever it encounters—corals, plants, shrimp, and shells. In doing so, the seabed itself is churned up and its parts remain suspended in the water column: parts such as sediment rich in carbon dioxide. 

Furrows in the seabed would cause greater oxygen absorption which, together with the emission of carbon dioxide, would disrupt the balance of gases in air and water, generating greater ocean acidification and further global warming.