Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Milton Keynes, UK.
Geobiology. 2012 Sep;10(5):434-44. doi: 10.1111/j.1472-4669.2012.00333.x. Epub 2012 Jun 14.
The weathering of volcanic rocks contributes significantly to the global silicate weathering budget, effecting carbon dioxide drawdown and long-term climate control. The rate of chemical weathering is influenced by the composition of the rock. Rock-dwelling micro-organisms are known to play a role in changing the rate of weathering reactions; however, the influence of rock composition on bio-weathering is unknown. Cyanobacteria are known to be a ubiquitous surface taxon in volcanic rocks. In this study, we used a selection of fast and slow growing cyanobacterial species to compare microbial-mediated weathering of bulk crystalline rocks of basaltic and rhyolitic composition, under batch conditions. Cyanobacterial growth caused an increase in the pH of the medium and an acceleration of rock dissolution compared to the abiotic controls. For example, Anabaena cylindrica increased the linear release rate (R(i)(l)) of Ca, Mg, Si and K from the basalt by more than fivefold (5.21-12.48) and increased the pH of the medium by 1.9 units. Although A. cylindrica enhanced rhyolite weathering, the increase in R(i)(l) was less than threefold (2.04-2.97) and the pH increase was only 0.83 units. The R(i)(l) values obtained with A. cylindrica were at least ninefold greater with the basalt than the rhyolite, whereas in the abiotic controls, the difference was less than fivefold. Factors accounting for the slower rate of rhyolite weathering and lower biomass achieved are likely to include the higher content of quartz, which has a low rate of weathering and lower concentrations of bio-essential elements, such as, Ca, Fe and Mg, which are known to be important in controlling cyanobacterial growth. We show that at conditions where weathering is favoured, biota can enhance the difference between low and high Si-rock weathering. Our data show that cyanobacteria can play a significant role in enhancing rock weathering and likely have done since they evolved on the early Earth.
火山岩的风化作用对全球硅酸盐风化预算有重要贡献，影响二氧化碳的消耗和长期气候控制。化学风化的速度受岩石组成的影响。已知居住在岩石中的微生物在改变风化反应速度方面起着作用；然而，岩石组成对生物风化的影响尚不清楚。蓝细菌是火山岩中普遍存在的表面分类群。在这项研究中，我们使用了一系列快速和慢速生长的蓝细菌物种，在批处理条件下比较了玄武岩和流纹岩组成的块状结晶岩的微生物介导风化作用。与非生物对照相比，蓝细菌的生长导致培养基 pH 值升高和岩石溶解加速。例如，Anabaena cylindrica 将玄武岩中 Ca、Mg、Si 和 K 的线性释放率（R(i)(l)）提高了五倍以上（5.21-12.48），并将培养基的 pH 值提高了 1.9 个单位。尽管 A. cylindrica 增强了流纹岩的风化作用，但 R(i)(l)的增加不到三倍（2.04-2.97），pH 值仅增加了 0.83 个单位。用 A. cylindrica 获得的 R(i)(l)值至少是玄武岩的九倍，而在非生物对照中，差异不到五倍。导致流纹岩风化速度较慢和生物量较低的因素可能包括石英含量较高，石英风化速度较慢，以及生物必需元素如 Ca、Fe 和 Mg 的浓度较低，这些元素已知对控制蓝细菌的生长很重要。我们表明，在有利于风化的条件下，生物群可以增强低硅和高硅岩石风化之间的差异。我们的数据表明，蓝细菌可以在增强岩石风化方面发挥重要作用，并且自从它们在早期地球上进化以来就可能已经发挥了作用。
