Microbial Diversity and Cyanobacterial Production in Dziani Dzaha Crater Lake, a Unique Tropical Thalassohaline Environment
|Author(s)||Leboulanger Christophe1, Agogue Helene2, Bernard Cecile3, Bouvy Marc1, Carre Claire1, Cellamare Maria3, 7, Duval Charlotte3, Fouilland Eric4, Got Patrice4, Intertaglia Laurent5, Lavergne Celine2, Le Floc'h Emilie4, Roques Cecile4, Sarazin Gerard6|
|Affiliation(s)||1 : Inst Rech Dev, UMR MARBEC, Sete Montpellier, France.
2 : CNRS, UMR LIENSs, La Rochelle, France.
3 : Museum Natl Hist Nat, UMR MCAM, Paris, France.
4 : CNRS, UMR MARBEC, Sete Montpellier, France.
5 : Univ Paris 06, Observ Oceanol Banyuls Sur Mer, Banyuls Sur Mer, France.
6 : Univ Paris Diderot, Inst Phys Globe Paris, UMR7154, Paris, France.
7 : Phytoquality, 15 Rue Petrarque, Paris, France.
|Source||Plos One (1932-6203) (Public Library Science), 2017-01 , Vol. 12 , N. 1 , P. e0168879 (28p.)|
|WOS© Times Cited||20|
This study describes, for the first time, the water chemistry and microbial diversity in Dziani Dzaha, a tropical crater lake located on Mayotte Island (Comoros archipelago, Western Indian Ocean). The lake water had a high level of dissolved matter and high alkalinity (10.614.5 g L-1 eq. CO32-, i.e. 160220 mM compare to around 22.5 in seawater), with salinity up to 52 psu, 1.5 higher than seawater. Hierarchical clustering discriminated Dziani Dzaha water from other alkaline, saline lakes, highlighting its thalassohaline nature. The phytoplankton biomass was very high, with a total chlorophyll a concentration of 524 to 875 mu g chl a L-1 depending on the survey, homogeneously distributed from surface to bottom (4 m). Throughout the whole water column the photosynthetic biomass was dominated (>97% of total biovolume) by the filamentous cyanobacteria Arthrospira sp. with a straight morphotype. In situ daily photosynthetic oxygen production ranged from 17.3 to 22.2 g O-2 m(-2) d(-1), consistent with experimental production / irradiance measurements and modeling. Heterotrophic bacterioplankton was extremely abundant, with cell densities up to 1.5 108 cells mL(-1) in the whole water column. Isolation and culture of 59 Eubacteria strains revealed the prevalence of alkaliphilic and halophilic organisms together with taxa unknown to date, based on 16S rRNA gene analysis. A single cloning-sequencing approach using archaeal 16S rDNA gene primers unveiled the presence of diverse extremophilic Euryarchaeota. The water chemistry of Dziani Dzaha Lake supports the hypothesis that it was derived from seawater and strongly modified by geological conditions and microbial activities that increased the alkalinity. Dziani Dzaha has a unique consortium of cyanobacteria, phytoplankton, heterotrophic Eubacteria and Archaea, with very few unicellular protozoa, that will deserve further deep analysis to unravel its uncommon diversity. A single taxon, belonging to the genus Arthrospira, was found responsible for almost all photosynthetic primary production.