Contribution of microbial photosynthesis to peatland carbon uptake along a latitudinal gradient

Samuel Hamard (1) , Regis Céréghino (1) , Maialen Barret (1) , Anna Sytiuk (1) , Enrique Lara (2) , Ellen Dorrepaal (3) , Paul Kardol (4) , Martin Küttim (5) , Mariusz Lamentowicz (6) , Joséphine Leflaive (1) , Gaël Le Roux (1) , Eeva‐stiina Tuittila (7) , Vincent Jassey (1)

1 LEFE - Laboratoire Ecologie Fonctionnelle et Environnement
2 RJB - Real Jardín Botánico de Madrid
3 Umeå University
4 SLU - Swedish University of Agricultural Sciences = Sveriges lantbruksuniversitet
5 Tallinn University
6 UAM - Uniwersytet im. Adama Mickiewicza w Poznaniu = Adam Mickiewicz University in Poznań
7 University of Eastern Finland

Phototrophic microbes, also known as micro-algae, display a high abundance in many terrestrial surface soils. They contribute to atmospheric carbon dioxide fluxes through their photosynthesis, and thus regulate climate similar to plants. However, microbial photosynthesis remains overlooked in most terrestrial ecosystems. Here, we hypothesize that phototrophic microbes significantly contribute to peatland C uptake, unless environmental conditions limit their development and their photosynthetic activity. To test our hypothesis, we studied phototrophic microbial communities in five peatlands distributed along a latitudinal gradient in Europe. By means of metabarcoding, microscopy and cytometry analyses, as well as measures of photosynthesis, we investigated the diversity, absolute abundance and photosynthetic rates of the phototrophic microbial communities. We identified 351 photosynthetic prokaryotic and eukaryotic operational taxonomic units (OTU) across the five peatlands. We found that water availability and plant composition were important determinants of the composition and the structure of phototrophic microbial communities. Despite environmental shifts in community structure and composition, we showed that microbial C-fixation rates remained similar along the latitudinal gradient. Our results further revealed that phototrophic microbes accounted for approximately 10% of peatland C uptake. Synthesis. Our findings show that phototrophic microbes are extremely diverse and abundant in peatlands. While species turnover with environmental conditions, microbial photosynthesis similarly contributed to peatland C uptake at all latitudes. We estimate that phototrophic microbes take up around 75 MT CO2 per year in northern peatlands. This amount roughly equals the magnitude of projected peatland C loss due to climate warming and highlight the importance of phototrophic microbes for the peatland C cycle

Mots clés: Algae; Carbon cycle; Metabarcoding; Microbial diversity; Peatland; Photosynthesis; Phototrophs; Primary productivity

Domaines: Ecosystèmes; Microbiologie et Parasitologie

Samuel Hamard, Regis Céréghino, Maialen Barret, Anna Sytiuk, Enrique Lara, et al.. Contribution of microbial photosynthesis to peatland carbon uptake along a latitudinal gradient. Journal of Ecology, 2021, RECONCILING RESILIENCE ACROSS ECOLOGICAL SYSTEMS, SPECIES AND SUBDISCIPLINES, 109 (9), pp.3424-3441. ⟨10.1111/1365-2745.13732⟩. ⟨hal-03373869⟩