August 18, 2021 — Microscopic marine life plays a fundamental role in the health of the ocean and, ultimately, the planet. Just like plants on land, tiny phytoplankton use photosynthesis to consume carbon dioxide and convert it into organic matter and oxygen. This biological transformation is known as marine primary productivity.
In a new study in Nature Geoscience this week, MBARI Senior Scientist Ken Johnson and former MBARI postdoctoral fellow Mariana Bif demonstrated how a fleet of robotic floats could revolutionize our understanding of primary productivity in the ocean on a global scale.
Data collected by these floats will allow scientists to more accurately estimate how carbon flows from the atmosphere to the ocean and shed new light on the global carbon cycle. Changes in phytoplankton productivity can have profound consequences, like affecting the ocean’s ability to store carbon and altering ocean food webs. In the face of a changing climate, understanding the ocean’s role in taking carbon out of the atmosphere and storing it for long periods of time is imperative.
“Based on imperfect computer models, we’ve predicted primary production by marine phytoplankton will decrease in a warmer ocean, but we didn’t have a way to make global-scale measurements to verify models. Now we do,” said MBARI Senior Scientist Ken Johnson.
By converting carbon dioxide into organic matter, phytoplankton not only support oceanic food webs, they are the first step in the ocean’s biological carbon pump.
Phytoplankton consume carbon dioxide from the atmosphere and use it to build their bodies. Marine organisms eat those phytoplankton, die, and then sink to the deep seafloor. This organic carbon is gradually respired by bacteria into carbon dioxide. Since a lot of this happens at great depths, carbon is kept away from the atmosphere for long periods of time. This process sequesters carbon in deep-sea water masses and sediments and is a crucial component in modeling Earth’s climate now and in the future.