Influence of microbial photosynthesis on tufa stromatolite formation and ambient water chemistry, SW Japan
Influence of microbial photosynthesis on tufa stromatolite formation and ambient water chemistry, SW Japan
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DOI：
10.1016/j.gca.2010.06.025
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发表时间：
2010-09-15
影响因子：
5
通讯作者：
Kano, Akihiro
中科院分区：
文献类型：
--
作者：
Shiraishi, Fumito;Okumura, Tomoyo;Kano, Akihiro
光合作用对石灰华叠层石的形成和环境水化学的影响进行了研究，在两个充分研究流沉积在日本西南部的石灰华（白川和下仓田）。两条溪流中的钙华叠层石由细粒方解石晶体组成，显示出年度分层，并由一些丝状蓝藻以及非光养细菌定殖。pH值，O-2，和Ca 2+附近的叠层石表面（扩散边界层; DBL）的微电极测量显示，调查石灰华叠层石是由光合作用诱导的碳酸钙沉淀（PCP）：蓝藻光合作用诱导方解石沉淀在光照条件下，而呼吸的蓝藻和非光合细菌抑制沉淀在黑暗中。在被调查的河流的较低位置的大量水化学显示，白天Ca 2+浓度和碱度的下降，预计五氯苯酚的显着影响，而其他预期的变化，增加pH值，没有观察到。为了研究这种差异，采用半原位微电极测量的新方法进行精确的定量计算。计算结果表明，所观察到的Ca 2+浓度和碱度的下降是由五氯苯酚引起的，并预计伴随的pH值的增加是在一个传统的pH计的检测水平。虽然PCP的量应该受到光照强度的显著影响，但在下仓田的观测显示，阴天的PCP量仍然占晴天的约80%。尽管五氯苯酚的显着作用，石灰华叠层石的形成，五氯苯酚只占约10%的沉淀方解石在调查流，这表明，石灰华叠层石，流中的特征存款，负责只有一小部分的方解石沉淀，其余的被认为是无机沉淀在无生物膜基板。(C)2010爱思唯尔有限公司版权所有。
Photosynthetic influences on tufa stromatolite formation and ambient water chemistry were investigated at two well-studied streams depositing tufa in Southwestern Japan (Shirokawa and Shimokuraida). The tufa stromatolites in both streams are composed of fine-grained calcite crystals showing annual lamination, and colonized by a number of filamentous cyanobacteria as well as non-phototrophic bacteria. Microelectrode measurements of pH, O-2, and Ca2+ near the stromatolite surface (the diffusive boundary layer; DBL) revealed that the investigated tufa stromatolites are formed by photosynthesis-induced CaCO3 precipitation (PCP): cyanobacterial photosynthesis induces calcite precipitation under light conditions, while respiration of cyanobacteria and non-phototrophic bacteria inhibits precipitation in the dark. The bulk water chemistry at the lower sites of the investigated streams showed the daytime decreases of Ca2+ concentration and alkalinity that was expected for significant influence of PCP, while the other expected change, increased pH, was not observed. In order to examine this discrepancy, a novel approach using semi-in situ microelectrode measurements was applied to perform precise quantitative calculations. The calculation results demonstrated that the observed Ca2+ concentration and alkalinity decreases were caused by PCP, and that the concomitant pH increase was expected to be under the detection level of a conventional pH meter. Although the amount of PCP is supposed to be significantly affected by light intensity, observations in Shimokuraida revealed that the amount of PCP on cloudy day nonetheless accounted for about 80% of that on sunny day. Despite the significant role of PCP for tufa stromatolite formation, PCP accounted for only about 10% of the precipitated calcite in the investigated streams, which indicates that tufa stromatolites, the characteristic deposits in the streams, are responsible for only a small portion of calcite precipitation, and the rest is considered to precipitate inorganically at biofilm-free substrates. (C) 2010 Elsevier Ltd. All rights reserved.