Department of Wildlife, Fisheries and Aquaculture, MS, USA.
Department of Wildlife, Fisheries and Aquaculture, MS, USA.
Water Res. 2015 Dec 15;87:193-201. doi: 10.1016/j.watres.2015.09.028. Epub 2015 Sep 16.
Enhancing wetland characteristics in agricultural drainage ditches with the use of low-grade weirs, has been identified as a best management practice (BMP) to mitigate nutrient runoff from agriculture landscapes. A major objective of utilizing low-grade weirs as a BMP includes fostering environments suitable for the biogeochemical removal of nitrogen via denitrification. This study examined the spatial resolution of microbial communities involved in denitrification in agricultural drainage systems fitted with low-grade weirs. Appropriate sampling scales of microbial communities were investigated using 16S rRNA and denitrification functional genes nosZ, nirS, and nirK via quantitative polymerase chain reaction (qPCR) and terminal-restriction fragment length polymorphism (T-RFLP) analysis. Genes 16S rRNA, nosZ, and nirS were all successfully detected in soil samples, while nirK was below the detection limit throughout the study. Utilizing a combination of three sampling regimes (management, reach, catchment) was found to be effective in capturing microbial community patterns, as ANOVA results revealed nosZ gene abundance was significantly greater at the management rather than reach scale (p = 0.045; F = 3.311), although, no significant differences were observed in 16S rRNA or nirS between sampling scales (p > 0.05). A Pearson correlation matrix confirmed that 16S rRNA and nosZ gene abundances were positively correlated with soil carbon (C), nitrogen (N), and moisture, while nirS abundance was only positively correlated with soil C and soil moisture. This highlights the potential for wetland-like characteristics to be recovered in agricultural drainage systems, as weir proximity is observed to enhance soil moisture and conditions for N remediation. This study provides the basis for additional investigations of these unique environments in the Mississippi Alluvial Valley and a starting point for adaptive management to enhance agricultural drainage systems for microbial communities towards nutrient remediation goals.
利用低等级堰增强农业排水渠的湿地特性已被确定为减轻农业景观养分径流的最佳管理实践（BMP）。利用低等级堰作为 BMP 的主要目标之一是促进适合生物地球化学去除氮的反硝化环境。本研究检查了配备低等级堰的农业排水系统中参与反硝化的微生物群落的空间分辨率。通过定量聚合酶链反应（qPCR）和末端限制性片段长度多态性（T-RFLP）分析，使用 16S rRNA 和反硝化功能基因 nosZ、nirS 和 nirK 研究了微生物群落的适当采样尺度。基因 16S rRNA、nosZ 和 nirS 均成功检测到土壤样本，而 nirK 在整个研究中均低于检测限。结果表明，采用三种采样方案（管理、河段、集水区）能够有效地捕捉微生物群落模式，因为 ANOVA 结果表明，nosZ 基因丰度在管理尺度而非河段尺度上显著更高（p = 0.045；F = 3.311），尽管 16S rRNA 或 nirS 之间的采样尺度无显著差异（p > 0.05）。Pearson 相关矩阵证实，16S rRNA 和 nosZ 基因丰度与土壤碳（C）、氮（N）和水分呈正相关，而 nirS 丰度仅与土壤 C 和土壤水分呈正相关。这突出表明在农业排水系统中可以恢复类似湿地的特征，因为观察到堰的接近度可提高土壤水分和 N 修复条件。本研究为在密西西比河冲积谷进一步研究这些独特环境提供了基础，也为增强农业排水系统的微生物群落朝着营养修复目标进行自适应管理提供了起点。
