Dissimilatory reduction of nitrate to ammonium, not denitrification or anammox, dominates benthic nitrate reduction in tropical estuaries
Dissimilatory reduction of nitrate to ammonium, not denitrification or anammox, dominates benthic nitrate reduction in tropical estuaries
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DOI：
10.4319/lo.2011.56.1.0279
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发表时间：
2011-01-01
影响因子：
4.5
通讯作者：
Nedwell, David B.
中科院分区：
文献类型：
--
作者：
Dong, Liang F.;Sobey, Milika Naqasima;Nedwell, David B.
我们测量了底栖反硝化（DN）和异化还原硝酸盐铵（DNRA）使用同位素配对技术在泰国（Mae Klong），印度尼西亚（Cisadane），斐济（Vunidawa-Rewa）在雨季，旱季和中间季节沿着每个河口的盐度梯度在三个热带河口。DNRA占主导地位。厌氧氨氧化酶（AN）最初进行了测量，但无论是AN活性，也没有AN细菌相关的16 S核糖体RNA基因在任何河口检测。DN为零或极低，驱动水柱硝酸盐，而不是从底栖硝化-DN。DN过程中无N_2O生成。在河口水N2 O饱和度低，除了在营养印尼河口，热带河口，因此可能是只有小的N2 O来源。底栖生物硝酸盐还原受硝酸盐限制，当实验增加硝酸盐时，DN略有增加，但DNRA增加比例更大。DNRA的优势，DN在热带河口可能是由于一个充满活力的优势（更大的标准自由能变化，DG度）的硝酸盐氨化酶在竞争有限的硝酸盐时，也更高的亲和力硝酸盐的硝酸盐氨化酶。在热带温度下，这三个过程的发生顺序为DNRA > DN > AN。相比之下，温带河口，在较低的温度和较高的硝酸盐浓度，表现出比例更高的AN和DN的水平。西沙丹河口成为缺氧在旱季，高铵和硫化物，但没有硝酸盐还原，因为缺乏硝酸盐。添加硝酸盐刺激高速率的自养DN驱动的硫化物，但不是DNRA。
We measured benthic denitrification (DN) and dissimilatory reduction of nitrate to ammonium (DNRA) using the isotope-pairing technique in three tropical estuaries in Thailand (Mae Klong), Indonesia (Cisadane), and Fiji (Vunidawa-Rewa) during rainy, dry, and intermediate seasons along the salinity gradient of each estuary. DNRA dominated. Anammox (AN) was measured initially but neither AN activity nor AN bacteria-related 16S ribosomal RNA genes were detected in any of the estuaries. DN was either zero or extremely low, driven by water column nitrate and not from benthic nitrification-DN. N2O was not formed during DN. N2O saturations in estuary water were low, except in the nutrified Indonesian estuary, and tropical estuaries are therefore likely to be only small sources of N2O. Benthic nitrate reduction was nitrate limited; when nitrate was enhanced experimentally, DN increased slightly, but DNRA increased proportionately much more. Predominance of DNRA over DN in tropical estuaries may be due both to an energetic advantage (greater standard free energy change, DG degrees) of nitrate ammonifiers over denitrifiers when competing for limited nitrate, and also to higher affinity for nitrate by the nitrate ammonifiers. At tropical temperatures the three processes occur in the order DNRA > DN > AN. In contrast, temperate estuaries, at lower temperature and higher nitrate concentrations, exhibit proportionately greater levels of AN and DN. The Cisadane estuary became anoxic during the dry season, with high ammonium and sulfide, but no nitrate reduction because of lack of nitrate. Addition of nitrate stimulated high rates of autotrophic DN driven by sulfide, but not DNRA.