Geochemistry of an endorheic thalassohaline ecosystem: the Dziani Dzaha crater lake (Mayotte Archipelago, Indian Ocean)

Gérard Sarazin (1) , Didier Jézéquel (1) , Christophe Leboulanger (2) , Eric Fouilland (2) , Emilie Le Floc'H (2) , Marc Bouvy (2) , Emmanuelle Gérard (1) , Hélène Agogué (3) , Cécile Bernard (4) , Mylène Hugoni (5) , Vincent Grossi (6) , Marc Troussellier (7, 2) , Magali Ader (1)

1 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
2 UMR MARBEC - MARine Biodiversity Exploitation and Conservation
3 LIENSs - LIttoral ENvironnement et Sociétés
4 MNHN - Muséum national d'Histoire naturelle
5 LEM - Laboratoire d'Ecologie Microbienne - UMR 5557
6 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
7 CNRS - Centre National de la Recherche Scientifique

Dziani Dzaha is a maar the age of which is close to 4000 years. While its water is thought to have originated from seawater it is now considered as an extreme environment due to its hypersaline and alkaline characteristics. Those extreme features have led to the simplification of the trophic network. Cyanobacteria account for up to 95% of the photosynthetic biomass. The main biogeochemical processes, i.e. photosynthesis, bacterial sulfate reduction and methanogenesis could explain the current water composition. As far as we know, this ecosystem could be unique on Earth, extending the nature and chemical limits of aquatic inland ecosystems.

Mots clés: Methane emission; Cyanobacteria; Endorheic ecosystem; Thalassohaline lake; Biogeochemistry; Mayotte

Domaines: Sciences de l'environnement

Gérard Sarazin, Didier Jézéquel, Christophe Leboulanger, Eric Fouilland, Emilie Le Floc'H, et al.. Geochemistry of an endorheic thalassohaline ecosystem: the Dziani Dzaha crater lake (Mayotte Archipelago, Indian Ocean). Comptes Rendus Géoscience, 2020, ⟨10.5802/crgeos.43⟩. ⟨hal-03252301⟩