Commonwealth Scientific and Industrial Research Organisation, Land and Water, Waite Road, Urrbrae, 5064, Australia.
Commonwealth Scientific and Industrial Research Organisation, Agriculture & Food, Waite Road, Urrbrae, 5064, Australia; Department of Natural Resources and the Environment, University of New Hampshire, College Road, Durham, NH, 03824, USA.
Environ Pollut. 2020 Aug;263(Pt A):114411. doi: 10.1016/j.envpol.2020.114411. Epub 2020 Mar 25.
The long-term effect of heavy metals on soil microbial communities and their function is relatively unknown and little work has been done in field settings. To address this gap, we revisited a field-based experiment, 12 years after the application of copper (Cu) to agricultural soils, with treatment concentrations ranging from 0 to 3310 mg Cu kg soil. We measured the long-term effects of Cu exposure to soils using multiple functionality assessments and environmental DNA-based community analyses. The assessment results revealed that soils that received moderate to high Cu doses had still not recovered functionality 12-years post exposure. However, plots that received doses of 200 mg kg Cu or less appeared to have a functionality index not dissimilar to control plots. Environmental DNA analyses of the microbial communities revealed a high level of beta diversity in low Cu treatment plots, whereas communities within high Cu treatment plots had similar community structures to one another (low beta diversity), indicating that specific Cu-tolerant or dormant taxa are selected for in high-Cu environments. Interestingly, high Cu plots had higher within-sample taxa counts (alpha diversity) compared with controls and low Cu plots. We hypothesise that taxa in high Cu plots activated dormancy mechanisms, such that their genetic signal remained present, whilst the functionality of the soil was reduced. Many species identified in high Cu plots are known to have associated dormancy mechanisms and survive in high stress environments. Understanding how these mechanisms collectively contribute to contaminant outcomes is of great importance for the goals of predicting and managing microbial communities and their function. As we found that Cu concentrations above 200 mg kg can cause significant functionality loss and a selective pressure on microbial communities, it is recommended that Cu concentrations above 200 mg kgare avoided in agricultural soils.
重金属对土壤微生物群落及其功能的长期影响尚不清楚，而且在野外环境中很少开展相关工作。为了解决这一空白，我们重新审视了一项基于野外的实验，该实验在向农业土壤中施加铜（Cu）12 年后进行，处理浓度范围从 0 到 3310mg Cu kg-1 土壤。我们使用多种功能评估和基于环境 DNA 的群落分析来测量 Cu 暴露对土壤的长期影响。评估结果表明，在暴露 12 年后，接受中高 Cu 剂量的土壤仍未恢复功能。然而，接受 200mg kg-1 Cu 或更低剂量的土壤的功能指数与对照土壤相似。对微生物群落的环境 DNA 分析显示，低 Cu 处理土壤中具有很高的 beta 多样性，而高 Cu 处理土壤中的群落结构彼此相似（beta 多样性低），表明在高 Cu 环境中选择了特定的 Cu 耐受或休眠类群。有趣的是，高 Cu 土壤中的样本内分类群计数（alpha 多样性）高于对照和低 Cu 土壤。我们假设高 Cu 土壤中的分类群激活了休眠机制，因此它们的遗传信号仍然存在，而土壤的功能则降低了。在高 Cu 土壤中发现的许多物种都具有休眠机制，并在高压力环境中存活。了解这些机制如何共同导致污染物的结果对预测和管理微生物群落及其功能的目标具有重要意义。由于我们发现 Cu 浓度高于 200mg kg-1 会导致显著的功能丧失和对微生物群落的选择性压力，因此建议在农业土壤中避免 Cu 浓度高于 200mg kg-1。
