Characterization of the key pathways of dissimilatory nitrate reduction and their response to complex organic substrates in hyporheic sediments
Characterization of the key pathways of dissimilatory nitrate reduction and their response to complex organic substrates in hyporheic sediments
复制标题
DOI：
10.4319/lo.2012.57.2.0387
复制
发表时间：
2012-03
影响因子：
4.5
通讯作者：
K. Lansdown;M. Trimmer;C. Heppell;F. Sgouridis;Sami Ullah;A. Heathwaite;A. Binley;Hao Zhang
中科院分区：
文献类型：
--
作者：
K. Lansdown;M. Trimmer;C. Heppell;F. Sgouridis;Sami Ullah;A. Heathwaite;A. Binley;Hao Zhang
从浅滩和水池中收集的河床沉积物的实验室孵育用于量化地下水补给河流的潜流区异化硝酸盐还原的潜在途径。从英国坎布里亚郡利斯河河床5 cm至86 cm深度处收集的沉积物与一套15 N标记的底物（15 NO −3、15 NH +4和14 NO −3）一起孵育，以定量通过反硝化、异化硝酸盐还原为铵（DNRA）和厌氧氨氧化（anammox）进行的硝酸盐还原。反硝化作用是异化硝酸盐还原在潜流沉积物中的主导途径，虽然15 N从铵库的恢复表明，DNRA也是活跃的。在15 NH +4和14 NO −3的培养过程中，29 N2的产生证实了厌氧氨氧化的潜力，但它比反硝化作用小得多。潜在的反硝化速率最高，在浅层沉积物和衰减指数与深度之后。浅滩沉积物和池塘沉积物的反硝化活性存在明显差异。在15 N-N2的生产稳定后，我们加入了细菌蛋白胨的加标物，以确定复杂有机底物对反硝化潜力的影响。反硝化的潜在速率均匀增加，在所有的沉积物深度，但总的有机基质燃料的反硝化量随深度显着下降，从90%在浅沉积物中的30%，在最深的沉积物。此外，15 NO −3中有相当一部分无法解释，这表明高达87%的15 NO −3已被最深的沉积物同化。
Laboratory incubations with river‐bed sediment collected from riffles and pools were used to quantify potential pathways of dissimilatory nitrate reduction in the hyporheic zone of a groundwater‐fed river. Sediments collected from between 5‐cm and 86‐cm depth in the bed of the River Leith, Cumbria, United Kingdom, were incubated with a suite of 15N‐labeled substrates (15NO−3, 15NH+4, and 14NO−3) to quantify nitrate reduction via denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonium oxidation (anammox). Denitrification was the dominant pathway of dissimilatory nitrate reduction in the hyporheic sediments, although recovery of 15N from the ammonium pool indicated that DNRA was also active. The potential for anammox was confirmed by the production of 29N2 during the 15NH+4 and 14NO−3 incubation, but it was much smaller than denitrification. Potential rates of denitrification were highest in shallow sediments and decayed exponentially with depth thereafter. There were clear differences in denitrification activity between riffle and pool sediments. After the production of 15N‐N2 had stabilized, we added a spike of bacteriological peptone to determine the effect of complex organic substrates on denitrification potential. The potential rate of denitrification increased uniformly at all sediment depths but the total amount of denitrification fueled by the organic substrates decreased markedly with depth, from 90% in the shallow sediments to 30% in the deepest sediments. In addition, a considerable fraction of the 15NO−3 could not be accounted for, which suggested that up to 87% of it had been assimilated in the deepest sediments.