According to a scientific study published Wednesday in the journal Nature, the ocean stores 20 percent more carbon through phytoplankton than previously thought.

“This is a very robust estimate that reinforces the role of ocean biology in long-term carbon sinks,” Frédéric Le Moine, an oceanographer and marine biologist at the CNRS who co-authored the study with Chinese and American researchers, told AFP.

According to the CNRS statement, the new estimate is 15 billion tons per year, which is about 20% more than the estimates mentioned by the IPCC (Intergovernmental Panel on Climate Change) in 2021.

This storage is made possible by phytoplankton, which convert CO2 into organic tissue through photosynthesis. When some of this phytoplankton dies, it falls from the surface to the bottom of the ocean in the form of “marine snow.”

Marine snow “flakes” are actually organic materials (decomposed animals, excrement, silt, etc.) that fall from the upper or middle layer of water into the ocean depths. During the fall, which can last up to several weeks, the scales, sticky as a spider’s web, accumulate a substance and reach a diameter of several centimeters. Along the way, some of them are eaten by sea creatures, and what remains settles to the bottom, annually collecting sea snow, which decomposes over time.

To measure these “marine snow” flows, the researchers used “existing databases of ocean carbon concentrations measured by oceanographic vessels,” the researcher explains. “Thanks to this numerical simulation, we were able to reconstruct global ocean currents, especially in regions where there were absolutely no current measurements.

“The next logical step is to estimate how much (carbon) actually reaches the ocean floor” at an average depth of 3,800 meters without being ingested by marine organisms, Le Moin notes.

When it reaches the ocean floor, this “marine snow” turns into sediments and rocks, storing carbon for tens of thousands of years.

The researchers’ assessment shows that “the preservation of marine biodiversity is crucial to ensure this process of biological carbon pumping, because we are dealing with an even greater flow than previously thought”, emphasizes the researcher from the Laboratory of Marine Environmental Sciences (LEMAR). from Pluzane, near Brest.

“This process takes tens of thousands of years and is not enough to offset the current increase in CO2 emissions,” he notes.

In addition, “global warming could weaken this biological carbon pump,” he warns.

Currently, it is believed that the ocean absorbs about 30% of the carbon released into the atmosphere as a result of human activity.