title: Community structure and activity of a highly dynamic and nutrient-limited hypersaline microbial mat in Um Alhool Sabkha, Qatar.
abstract: The Um Alhool area in Qatar is a dynamic evaporative ecosystem that receives seawater from below as it is surrounded by sand dunes. We investigated the chemical composition, the microbial activity and biodiversity of the four main layers (L1-L4) in the photosynthetic mats. Chlorophyll a (Chl a) concentration and distribution (measured by HPLC and hyperspectral imaging, respectively), the phycocyanin distribution (scanned with hyperspectral imaging), oxygenic photosynthesis (determined by microsensor), and the abundance of photosynthetic microorganisms (from 16S and 18S rRNA sequencing) decreased with depth in the euphotic layer (L1). Incident irradiance exponentially attenuated in the same zone reaching 1% at 1.7-mm depth. Proteobacteria dominated all layers of the mat (24%-42% of the identified bacteria). Anoxygenic photosynthetic bacteria (dominated by Chloroflexus) were most abundant in the third red layer of the mat (L3), evidenced by the spectral signature of Bacteriochlorophyll as well as by sequencing. The deep, black layer (L4) was dominated by sulfate reducing bacteria belonging to the Deltaproteobacteria, which were responsible for high sulfate reduction rates (measured using 35S tracer). Members of Halobacteria were the dominant Archaea in all layers of the mat (92%-97%), whereas Nematodes were the main Eukaryotes (up to 87%). Primary productivity rates of Um Alhool mat were similar to those of other hypersaline microbial mats. However, sulfate reduction rates were relatively low, indicating that oxygenic respiration contributes more to organic material degradation than sulfate reduction, because of bioturbation. Although Um Alhool hypersaline mat is a nutrient-limited ecosystem, it is interestingly dynamic and phylogenetically highly diverse. All its components work in a highly efficient and synchronized way to compensate for the lack of nutrient supply provided during regular inundation periods.
authors.affiliation: Department of Biological and Environmental Sciences, Qatar University, Doha, Qatar.
authors.forename: Roda
authors.initials: R
authors.lastname: Al-Thani
authors.affiliation: Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Mohammad A A
authors.initials: MA
authors.lastname: Al-Najjar
authors.affiliation: Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Abdul Munem
authors.initials: AM
authors.lastname: Al-Raei
authors.affiliation: Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Ferdelman
authors.affiliation: Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Nguyen M
authors.initials: NM
authors.lastname: Thang
authors.affiliation: Environmental Studies Center, Qatar University, Doha, Qatar.
authors.forename: Ismail
authors.initials: I
authors.lastname: Al Shaikh
authors.affiliation: Environmental Studies Center, Qatar University, Doha, Qatar.
authors.forename: Mehsin
authors.initials: M
authors.lastname: Al-Ansi
authors.affiliation: Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: de Beer
mesh_terms: D001105:Archaea / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D044822:Biodiversity; D041861:Chloroflexus / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D002734:Chlorophyll / Q000032:analysis*; D000077194:Chlorophyll A; D017753:Ecosystem; D064307:Microbiota; D010788:Photosynthesis; D020560:Proteobacteria / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D011780:Qatar; D012623:Seawater
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A