The word algae evokes the sea, yet there are also terrestrial algae and they can be found in deserts, peat bogs as well as on mountain tops…Vincent Jassey from the Functional Ecology and Environment Laboratory (CNRS, Toulouse INP, UT3 Paul Sabatier) and his team used machine learning modeling to demonstrate the importance of the role of soil algae in the carbon cycle, they published their study entitled “Contribution of soil algae to the global carbon cycle” in the journal “New Phytologist”.
Terrestrial algae are single-celled organisms that, like plants, capture CO2 atmosphere and thus contribute to the storage of carbon in the soil.
Vincent Jassey, the lead author of the study, explains:
“I work on peat bogs, and I realized that these algae were present in large quantities. I wanted to know what their contribution to the carbon cycle might be. Because, until then, in the plant kingdom, only plants were considered in terms of assimilation of carbon dioxide (CO2). However, we have shown that terrestrial algae also contribute significantly. »
Five million algae per gram of soil
Vincent Jassey and his team first sought to determine the distribution of terrestrial algae thanks to publications on the subject and it appeared that, if they are found in all regions of the globe, their quantity varies according to the ecosystem where they are found: from a few thousand to several million per gram, with an average of 5 million. The surprise for the researchers came from the fact that they are more abundant in acidic, moist and vegetated soils rather than in desert regions.
Predicting carbon productivity through modeling
The researchers enriched the environmental data of the algae with satellite data, temperature, vegetation, soil humidity, their CO2 content…and tested several algorithms to model the prediction of carbon productivity of the algae, the forest randomization proved to be more effective both in terms of predictions and margins of error.
They were thus able to observe that these algae captured approximately 3.6 gigatonnes of carbon per year, or 30% of CO2 emissions.2 emitted by man. These results contradict certain received ideas regarding the role of microorganisms in soils and demonstrate that, if microbial photosynthesis is a major component of aquatic ecosystems, it is also one of the majority of terrestrial ecosystems.
While it is necessary to improve the models, the study nevertheless revealed that these micro-algae are crucial organisms for the global carbon cycle.
The researchers say:
“These results change basic assumptions regarding the role of microbes in soil, showing that microbial photosynthesis is a major component not only of aquatic ecosystems but also of most terrestrial ecosystems, and underscore the key role of microalgae in the cycle global carbon. The protection of soil biodiversity has never been more important than today, when it is increasingly urgent to use all possibilities to reduce the level of CO2 in the atmosphere. »
Sources de l’article : Contribution of soil algae to the global carbon cycle
Vincent EJ Jassey, Romain Walcker, Paul Kardol, Stefan Geisen, Thierry Heger, Mariusz Lamentowicz, Samuel Hamard, Enrique Lara
https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.17950
