Carbon is an element that almost everyone has heard of, or knows a little something about. We know that about 20% of our bodies are made of carbon and that it is an essential building block of all living organisms, but carbon is also found in many non-living things as well (Science). But what you might not know is that carbon is constantly cycled in and out between the different ecosystems and terrain across the planet. This exchange is called the carbon cycle, the give-and-take of carbon between Earth’s living organisms (biosphere), air (atmosphere), water (hydrosphere), land (pedosphere) and the deep rocks and crust that is the center of the planet (lithosphere) (Woods Hole Oceanographic Institution). Different stages of the cycle can hold carbon for varying lengths of time. Each step in the cycle releases carbon at different times, thus, just the right balance of carbon needed to support life is maintained  (Science Learning Hub).

carbon cycle

The Atmosphere and the Ocean

The ocean plays a vital role as one of Earth’s main biogeochemical cycles that make life possible for all living creatures and organisms. When compared to the atmosphere, the total amount of carbon found in the ocean is 50 times higher than that of the air (NASA). That means just about half of the air we breathe comes from marine plants that undergo photosynthesis, the breakdown of carbon by plants to produce sugars. Because the ocean absorbs so much more carbon than it releases, it is often referred to as a “carbon sink” (Science Learning Hub). A sink can store carbon for extended periods of time, buried in the deepest part of the ocean and in the sediment lining the ocean floor. The variations of carbon dioxide (CO2) between the ocean and the atmosphere depends on several factors. When carbon is absorbed at the surface wind speed and the movement of marine organisms help to spread that carbon rich water throughout the rest of the ocean, effectively changing the concentration of CO2 in the ocean. Other factors that influence the differences of CO2 concentration in both the air and the water include temperature, alkalinity, photosynthesis and respiration by marine plants (NASA).


As the amount of fossil fuels being burned for combustion increases, so does the amount of carbon dioxide that is taken up by the ocean. Many marine organisms have adapted to take in and use this readily available source of carbon dioxide. For example, shelled organisms such as crustaceans, lobsters, mussels, clams, etc., use carbon to create calcium carbonate to build their shells and skeletons (Science Learning Hub). Carbon dioxide is also incorporated into the ocean’s food chain, meaning even more marine plants and organisms take in and use the carbon that is absorbed into the water from the atmosphere due to the carbon cycle (Woods Hole Oceanographic Institution).


The Ocean as a Biological Pump

NASA defines the ocean as a biological pump, meaning “the photosynthetic up take of atmospheric carbon dioxide by ocean microorganisms, resulting in long-term sequestration of carbon in the deep ocean via particle sinking, where is it removed from contact with the atmosphere for millions of years if the particles reach the bottom and are buried in sedimentary carbonates.” (NASA) So what in the world does that mean?

carbonAs carbon is absorbed on the ocean’s surface, fish and other organisms swimming near the surface help to stir that carbon rich water. As this surface water becomes mixed with the deeper ocean waters, the carbon begins to be absorbed by marine organisms and plants. However, some of that carbon rich water makes it all the way down to the bottom, where it is absorbed by rocks and sediment. Because marine organisms absorbed carbon while they were alive, when they die, carbon dioxide is released during the decaying process which occurs in deeper waters where their organic matter was laid to rest. This part of the carbon cycle is a huge contributor to the storing of carbon, for millions of years at a time (Science Learning Hub).


Final Thoughts

The carbon cycle is a major recycling process critical to the balance of carbon throughout the biosphere, not only for the land and the air of planet Earth, but for the ocean as well. The amount of carbon being expelled into the atmosphere and exchanged with the oceans affects all marine life and has both beneficial and harmful consequences. Carbon fluctuations can alter the water chemistry of the oceans and the organisms that dwell within. In this day and age, more and more carbon is being funneled through the carbon cycle; making scientific studies regarding the cycle and more adequate knowledge about how carbon sinks will affect Earth in the future that much more important.



“Carbon Cycle.” National Aeronautic and Space Administration. NASA, n.d. Web. 2016.

“The Ocean and the Carbon Cycle.” Science Learning Hub. The University of Waikato, 22 June 2010.

“Carbon Cycle.” Woods Hole Oceanographic Institution. N.p., 2016. Web.