Deep ocean: in search of microbes living on marine snow

When plankton living on the surface of the ocean die, they decompose and their remains sink to the deep sea in particulate form. This decomposing matter, known as "marine snow", looks strangely like snowflakes. This phenomenon represents one of the main "biological pumps" of atmospheric CO2 to the ocean. It also provides nutrients and essential energy for many deep-sea creatures. In this context, one of the main unknowns is the link between the diversity and activity of the prokaryotes (essentially bacteria and a few archaea) involved in the degradation of these particles.

During an oceanographic campaign in the North Atlantic, researchers from an international team used an instrument specially designed to collect and study these rare and very fragile particles. They both measured biomass production and carried out genetic analyses of the prokaryotes associated with them. They were thus able to accurately assess the activity of the different families of prokaryotes involved in the degradation of these marine snow particles.

They found that the activity of prokaryotes and the richness of their families are radically different depending on the speed at which particles fall in the mesopelagic zone, and that prokaryotes attached to particles seed the deep ocean by detaching or fragmenting them. These results highlight the crucial role of falling particles in the formation and maintenance of prokaryotic communities in the deep ocean. They also show the importance of these communities as a determining factor in the efficiency of the biological carbon pump in the deep ocean.

This approach, which links the occurrence of genes in the prokaryotic community to the biological carbon pump, is a promising approach that will enable more accurate predictions of the biogeochemistry of the deep ecosystem on a global scale.

Contacts

Christian Tamburini, MIO-OSU Institut Pythéas / Tel: 04 86 09 05 19

Frédéric Le Moigne, MIO-OSU Institut Pythéas

See online : The article on the INSU website

Notes

[1] This work was carried out by researchers from the Institut méditerranéen d'océanographie (MIO/PYTHÉAS, CNRS / Université de Toulon / IRD / AMU), in collaboration with a researcher from the NOC (Southampton, UK) who carried out the campaign and a researcher from the IGB (Stechnlin, Germany) who discussed the results and wrote the article.

To find out more...

Baumas C.M.J., Le Moigne F.A.J., Garel M., Bhairy N., Guasco S., Riou V., Armougom F., Grossart H.-P., Tamburini C. (2021). Mesopelagic microbial carbon production correlates with diversity across different marine particle fractions. ISME J (2021). https://doi.org/10.1038/s41396-020-00880-z

 

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