Abstract The epi-sedimentary microbial community of a shallow oxbow lake in the Colorado River floodplain was studied along a transect running from its concave margin to the center. Physico-chemical parameters characterized the lake as hypersaline (S = 38.8 ± 0.7), alkaline (pH = 8.0 ± 0.2), and stagnant. Core samples of the topmost sediment were taken at three equidistant points for a diatom analysis; furthermore, the easily-detachable microbial mat was sampled at the center of the lake. Diatoms were dominated by biraphid taxa with benthic or epiphytic habits, while planktonic taxa were scarce. The microbial mat consisted in a millimeter-layered bio-sedimentary structure, presenting high organic matter (36.0 ± 0.2%) and chlorophyll a (144.1 ± 8.1 µg Chl a g−1 DW sediment) contents. Filamentous cyanobacteria dominated the mat biomass in surface layers (0–6 mm), while motile benthic diatoms were the second-most abundant phototrophic group. Navicula salinicola was the dominant diatom. Heterotrophic components of community (proto- and metazoans) were also identified. Resistance biogenic structures such as chrysophyte stomatocysts and planktonic diatom resting spores, and abundant gypsum precipitates were found throughout, pointing to intrinsic hydro-ecological stress conditions (desiccation and salinity fluctuations) of an inland evaporitic system. This is the first report of microbial mats colonizing surface-sediments of an infilled oxbow lake.

中文翻译：

---

来自阿根廷科罗拉多河泛滥平原浅牛轭湖的微生物垫和表层沉积物群落

摘要 沿着从凹边缘到中心的横断面研究了科罗拉多河泛滥平原浅牛轭湖的表生沉积微生物群落。物理化学参数将该湖表征为高盐度 (S = 38.8 ± 0.7)、碱性 (pH = 8.0 ± 0.2) 和停滞。在三个等距点采集最顶层沉积物的岩心样本进行硅藻分析；此外，在湖中心对易于拆卸的微生物垫进行了采样。硅藻以具有底栖或附生习性的双蚜类群为主，而浮游类群很少。微生物垫由毫米层生物沉积结构组成，具有高有机质 (36.0 ± 0.2%) 和叶绿素 a (144.1 ± 8.1 µg Chl ag−1 DW 沉积物) 含量。丝状蓝藻在表层（0-6 毫米）的垫子生物量中占主导地位，而活动的底栖硅藻是第二丰富的光养类群。Navicula salinicola 是主要的硅藻。还鉴定了群落的异养成分（原生动物和后生动物）。整个过程中都发现了抗性生物结构，如金藻口囊和浮游硅藻静息孢子，以及丰富的石膏沉淀物，表明内陆蒸发系统的内在水生态压力条件（干燥和盐度波动）。这是第一份关于微生物垫在充满牛轭湖的表层沉积物中定居的报告。还鉴定了群落的异养成分（原生动物和后生动物）。整个过程中都发现了抗性生物结构，如金藻口囊和浮游硅藻静息孢子，以及丰富的石膏沉淀物，表明内陆蒸发系统的内在水生态压力条件（干燥和盐度波动）。这是第一份关于微生物垫定植于充满牛轭湖的表层沉积物的报告。还鉴定了群落的异养成分（原生动物和后生动物）。整个过程中都发现了抗性生物结构，如金藻口囊和浮游硅藻静息孢子，以及丰富的石膏沉淀物，表明内陆蒸发系统的内在水生态压力条件（干燥和盐度波动）。这是第一份关于微生物垫定植于充满牛轭湖的表层沉积物的报告。