Le Dr. Ramiro Logares est un expert en génomique environnementale (Instituto de Ciencias del Mar, Barcelone), il travaille depuis plus de 15 ans sur l'écologie et l'évolution des organismes unicellulaires marins.
Disentangling the mechanisms that shape the sunlit global-ocean microbiome
The smallest members of the sunlit-ocean microbiome (prokaryotes and picoeukaryotes) participate in a plethora of ecosystem functions with planetary-scale effects. Understanding the mechanisms determining the distribution of species composing this assemblage can help us better understand the links between microbiome change and ecosystem function. Yet, despite its great importance, the underlaying processes structuring the surface-ocean microbiome are barely known. Ecological theory predicts that the action of selection, dispersal and drift determines the distribution of species, therefore here we quantified the action of these processes on marine microbial assemblages by using community DNA-sequence data from both picoeukaryotes and prokaryotes collected during the Malaspina-2010 expedition. We found that contrasting mechanisms shape the sunlit-ocean microbiome: limited dispersal was the dominant process structuring picoeukaryotic communities, while a combination of limited dispersal, selection and drift shaped prokaryotic counterparts. By investigating associations between environmental parameters with both the structure of communities as well as species-abundances, we determined that the same environmental variables can exert different degrees of selection in picoeukaryotes and prokaryotes. In particular, selection via temperature seemed to influence strongly prokaryotic species associations, which was not observed in picoeukaryotes. Furthermore, we found that limited dispersal was manifested as stronger distance-decay effects in picoeukaryotes than in prokaryotes, typically within distances <1,000Km. Finally, drift appeared to have larger effects in prokaryotes than in picoeukaryotes. Altogether, our findings allow to start linking microbiome structure, ecological mechanisms and ecosystem function, generating predictions on, for example, whether or not environmental change could induce large or small fluctuations in the ocean’s microbiome.