School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, Republic of Korea.
School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, Republic of Korea.
Sci Total Environ. 2018 Aug 1;631-632:755-764. doi: 10.1016/j.scitotenv.2018.03.073. Epub 2018 Mar 16.
Hyporheic zones are considered hot spots for numerically vast and phylogenetically diverse microbial communities. However, biogeochemical effects of hyporheic zones have rarely been investigated in detail because of the difficulty in accurately measuring denitrification in these zones. To date, little is known about the hydroecology of hyporheic zones. The effect of changes in hydraulic conditions on the community variations of indigenous microorganisms and water quality was examined based on the depth of the hyporheic zone. In particular, we report on the use of the pyrosequencing technique to elucidate denitrifying bacteria (DNB) community profiles combined with the stable isotope composition of nitrate and hydrological patterns in the hyporheic zones to reveal whether denitrification occurs. δN-NO and δO-NO values of nitrate were analyzed to evaluate the transformation processes of nitrate in upwelling and downwelling areas and mixed zones. The isotope values indicated different origins of water in upwelling and downwelling zones and that denitrification occurred predominantly in the upwelling areas. Analyses of microbial communities in the hyporheic zone showed that the new genera, species, and isotope data were associated with the hydrological uniqueness of the hyporheic zones. The 16S rRNA sequences were determined and phylogenetic analysis revealed that the DNB communities distributed and gathered the genus Comamonas denitrificans within the mixing patterns of the hyporheic zones and that the relative scarcity of these microbes in these zones was caused by the lack of appropriate substrates. The delineation of the surface water-groundwater mixing zone was quantitatively determined by systematically combining the hydrological and heat transfer analyses and by comparing denitrifying bacteria communities and N isotope data. This study showed that pyrosequencing and isotopic approaches are useful for evaluating the transformation processes of nitrate at the upwelling and downwelling points of a hyporheic zone.
底栖带被认为是数量庞大且具有丰富遗传多样性的微生物群落的热点区域。然而，由于难以准确测量这些区域的反硝化作用，底栖带的生物地球化学效应很少被详细研究。迄今为止，人们对底栖带的水生态学知之甚少。本研究基于底栖带的深度，考察了水力条件变化对原生微生物群落变化和水质的影响。特别是，我们报告了使用焦磷酸测序技术来阐明反硝化细菌（DNB）群落的组成，以及硝酸盐的稳定同位素组成和底栖带的水文模式，以揭示反硝化作用是否发生。硝酸盐的δN-NO 和 δO-NO 值用于评估上升流和下降流区以及混合区硝酸盐的转化过程。同位素值表明上升流区和下降流区的水具有不同的来源，并且反硝化作用主要发生在上升流区。底栖带微生物群落的分析表明，新的属、种和同位素数据与底栖带的水文独特性有关。16S rRNA 序列的测定和系统发育分析表明，DNB 群落分布并聚集了混合模式下的 Comamonas denitrificans 属，而这些微生物在这些区域的相对匮乏是由于缺乏合适的底物。地表水-地下水混合带的划定是通过系统地结合水文和传热分析，并比较反硝化细菌群落和 N 同位素数据来定量确定的。本研究表明，焦磷酸测序和同位素方法可用于评估底栖带上升流和下降流点硝酸盐的转化过程。
