An article published in the journal “Limnology and Oceanography” describes a study on the circulation of carbon in the oceans. A team of researchers from Florida State University (FSU) studied the area between 100 and 1,000 meters of depth discovering that very simple organisms belonging to the group called Phaeodarea consume carbon-rich particles that are sinking before they reach the seabed, where they could otherwise be sequestered for millennia. They’re tiny organisms but they could have an impact on the carbon cycle and therefore on climate.

Phaeodarians (Phaeodarea or Phaeodaria), are a group of amoeboid eukaryotic organisms that are part of a larger group called Cercozoa. In what the team led by Mike Stukel of FSU called the oceans’ twilight zone, between 100 and 1,000 meters of depth, there are many Phaeodarea but also Radiolaria and Foraminifera, which together with Cercozoa form the large Rhizaria group. They have variable size that can be relatively large for microorganisms, over 600 micrometers. Generally, they’re not taken into account in carbon cycle studies for various reasons including their still vague classification.

So far, the studies focused on other microorganisms such as diatoms, unicellular algae whose importance was already known. In fact, they are one of the main groups of organisms that produce oxygen through photosynthesis. In addition to this they produce tiny shells that sink into the waters along with other fragments of matter of various kinds.

The carbon contained in the various fragments could end up on the seabed and remain sequestered there for millennia, coming out of the cycle that brings it from the atmosphere into the ocean, where it enters various organisms’ life cycles, only to be released again. Mike Stukel’s team used a sophisticated monitoring system to identify a higher than expected amount of microorganisms between 100 and 1,000 meters of depth that affect the carbon cycle.

In particular, the researchers identified microorganisms of one of the Phaeodarea families called Aulosphaeridae that could consume 20% and even more of the carbon-rich particles sinking from the surface of the water. This is a significant amount that determines an influence on carbon cycle.

The research was limited to one geographical area and ended up focusing mainly on one family of microorganisms. They’ll need to assess the variability in the presence not only of the various Phaeodarea but of the Rhizaria in general, in different marine areas and over time, to get a better idea of ​​their influence on carbon cycle. Given the importance of this element in climate change, it’s a type of research that could become prominent and extend our knowledge of the phenomena connected to climate.