Processes Forming Daily Lamination in a Microbe-Rich Travertine Under Low Flow Condition at the Nagano-yu Hot Spring, Southwestern Japan
Processes Forming Daily Lamination in a Microbe-Rich Travertine Under Low Flow Condition at the Nagano-yu Hot Spring, Southwestern Japan
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DOI：
10.1080/01490451.2013.791355
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发表时间：
2013-04
影响因子：
2.3
通讯作者：
T. Okumura;C. Takashima;F. Shiraishi;S. Nishida;A. Kano
中科院分区：
文献类型：
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作者：
T. Okumura;C. Takashima;F. Shiraishi;S. Nishida;A. Kano
在日本西南部长野汤温泉低流量地点形成的富含微生物的文石洞石中，确定了微生物过程的日常节律（亚毫米级层压）。连续观察和采样清楚地表明，层状结构由昼间富含微生物层（M 层）和夜间结晶层（C 层）组成。 M层起源于与Microcoleus sp.有关的丝状蓝细菌生长和向上迁移形成的生物膜，它可以快速滑动并分泌细胞外聚合物（EPS）。白天，由于 EPS 的钙结合能力，蓝藻生物膜的发育抑制了石灰华表面的文石沉淀。日落后，地表开始出现文石沉淀，好氧异养细菌分解EPS，诱导泥晶晶体沉淀。 C 层形成的早期阶段之后是扇形文石聚集体的非生物沉淀。尽管蓝藻在层层形成中发挥着重要作用，但它们在嵌入后 6-10 天内很容易降解，并且 M 层中剩余的开放空间稀疏地填充有晶体凝块。这些纹层形成过程与在高流量地点观察到的过程不同，在高流量地点，石灰华具有致密的霰石晶体结构。长野汤的微生物钙华在原位矿物沉淀、规则的亚毫米级层理和丝状微生物的排列方面与一些前寒武纪叠层石相似；因此，这些叠层石的层压可能以每天的节奏发生。这项研究证明的微生物过程可能会修正对古代叠层石形成的解释。
A daily rhythm of microbial processes, in terms of sub-mm order lamination, was identified for a microbe-rich aragonite travertine formed at a low-flow site of the Nagano-yu Hot Spring in Southwestern Japan. Continuous observation and sampling clearly showed that the lamination consisted of diurnal microbe-rich layers (M-layers) and nocturnal crystalline layers (C-layers). The M-layers originated from biofilm formed by growth and upward migration of filamentous cyanobacteria related to Microcoleus sp., which can rapidly glide and secrete extracellular polymeric substances (EPS). During the daytime, cyanobacterial biofilm development inhibited aragonite precipitation on the travertine surface due to the calcium-binding ability of EPS. After sunset, aragonite precipitation started on the surface where aerobic heterotrophic bacteria decomposed EPS, which induced precipitation of micritic crystals. This early stage of C-layer formation was followed by abiotic precipitation of fan-shaped aragonite aggregates. Despite their major role in lamina formation, the cyanobacteria were readily degraded within 6–10 days after embedding, and the remaining open spaces in the M-layers were sparsely filled with crystal clots. These lamina-forming processes were different from those observed in a high-flow site where the travertine has a dense texture of aragonite crystals. The microbial travertine at Nagano-yu is similar to some Precambrian stromatolites in terms of in situ mineral precipitation, regular sub-mm order lamination, and arrangement of filamentous microbes; therefore, the lamination of these stromatolites possibly occur with a daily rhythm. The microbial processes demonstrated in this study may revise the interpretation of ancient stromatolite formation.