Emma Jamon-Haon will defend his thesis on Tuesday 16 December 2025 à 14h00 at the OCEANOMED Amphitheatre on the following topic: Heterogeneity of mangrove microbiotas: determinants of their biodiversity.
Join Zoom Meeting
Meeting ID: 917 5756 0872
Secret code: 158774
Members of the Jury
- Cristina Cravo-Laureau, Rapporteur, UPPA (IPREM), MCF
- Lionel Ranjard, Rapporteur, INRAE (Agroecology), DR
- Cédric Hubas, Examiner, MNHN (Borea), DR
- Anne Bousquet-Mélou, President of the jury, AMU (IMBE), DR
- Philippe Cuny, PhD supervisor, AMU (MIO), PR
- Cécile Militon, Thesis co-supervisor, AMU (MIO), MCF
Abstract
Mangroves are tropical forests that develop on sediments at the interface between land and sea. This thesis, based on 16S metabarcoding datasets and geochemical profiling of sediments from primarily French overseas mangroves, aimed to: (i) better characterize the pantropical diversity of mangrove sediment microbiotas, (ii) identify the major ecological processes structuring their assembly, and (iii) explore their seasonal dynamics in a region that remains poorly studied. The results showed that prokaryotes inhabiting mangrove sediments are predominantly affiliated with Proteobacteria, Chloroflexi, Desulfobacterota, Bacteroidota, Planctomycetota, Acidobacteriota, Actinobacteriota, Firmicutes, Crenarchaeota, and Thermoplasmatota. The core microbiota represents only 1.6-4% of the total sequences, underscoring the importance and diversity of transient prokaryotes in mangroves. Global diversity patterns reveal an asymmetry, with a potential hotspot of microbial diversity in the Indo-West Pacific (1.5-fold higher), particularly within the Indo-Malayan and East African bioregions. In coastal mangroves, diversity also follows a latitudinal gradient and is partly constrained by global dispersal barriers. Dispersal further exerts a strong influence on community distribution at the island scale (Guadeloupe, Martinique, and Mayotte). Mangrove sediment microbiotas exhibit pronounced local compositional heterogeneity, shaped by the biogeochemical, geomorphological, and anthropogenic context of each mangrove system. In the model case of the Cayenne estuary (French Guiana), microbial structure, composition, and molecular biomass responded in contrasting ways to extreme seasonal hydrological conditions, reflecting the potential impacts of climate change on these communities. This work provides novel insights into the microbial communities of French overseas mangroves within a global framework and contributes more broadly to advancing the understanding of microbial ecology in mangrove ecosystems.
