Al-Thani Roda, Al-Najjar Mohammad A A, Al-Raei Abdul Munem, Ferdelman Tim, Thang Nguyen M, Al Shaikh Ismail, Al-Ansi Mehsin, de Beer Dirk
Department of Biological and Environmental Sciences, Qatar University, Doha, Qatar.
Max-Planck Institute for Marine Microbiology, Bremen, Germany.
PLoS One. 2014 Mar 21;9(3):e92405. doi: 10.1371/journal.pone.0092405. eCollection 2014.
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.
卡塔尔的乌姆阿尔胡勒地区是一个充满活力的蒸发生态系统，由于其被沙丘环绕，海水从下方涌入。我们研究了光合垫中四个主要层（L1 - L4）的化学成分、微生物活性和生物多样性。叶绿素a（Chl a）浓度和分布（分别通过高效液相色谱法和高光谱成像测量）、藻蓝蛋白分布（通过高光谱成像扫描）、产氧光合作用（由微传感器测定）以及光合微生物的丰度（来自16S和18S rRNA测序）在透光层（L1）中随深度降低。入射辐照度在同一区域呈指数衰减，在1.7毫米深度处达到1%。变形菌门在光合垫的所有层中占主导地位（占已鉴定细菌的24% - 42%）。无氧光合细菌（以绿弯菌属为主）在光合垫的第三红色层（L3）中最为丰富，细菌叶绿素的光谱特征以及测序都证明了这一点。深层黑色层（L4）由属于δ变形菌门的硫酸盐还原细菌主导，这些细菌导致了高硫酸盐还原率（使用35S示踪剂测量）。嗜盐菌成员是光合垫所有层中的主要古菌（92% - 97%），而线虫是主要的真核生物（高达87%）。乌姆阿尔胡勒光合垫的初级生产力速率与其他高盐度微生物光合垫相似。然而，硫酸盐还原率相对较低，这表明由于生物扰动，有氧呼吸对有机物质降解的贡献比硫酸盐还原更大。尽管乌姆阿尔胡勒高盐度光合垫是一个营养有限的生态系统，但有趣的是它充满活力且系统发育高度多样。其所有组成部分以高效且同步的方式运作，以弥补正常淹没期提供的营养供应不足。
