Nitrite dynamics in the open ocean - clues from seasonal and diurnal variations
Nitrite dynamics in the open ocean - clues from seasonal and diurnal variations
复制标题
DOI：
10.3354/meps09525
复制
发表时间：
2012-05
影响因子：
2.5
通讯作者：
Efrat Meeder;K. Mackey;A. Paytan;Yeala Shaked;D. Iluz;N. Stambler;T. Rivlin;A. Post;B. Lazar
中科院分区：
文献类型：
--
作者：
Efrat Meeder;K. Mackey;A. Paytan;Yeala Shaked;D. Iluz;N. Stambler;T. Rivlin;A. Post;B. Lazar
对于亚硝酸盐在含氧寡营养水体中的积累，提出了两种替代机制：（1）浮游植物的排泄或（2）铵的微生物氧化（硝化）。本研究根据红海亚喀巴湾溶解无机氮 (DIN) 物种（亚硝酸盐、铵、硝酸盐）和叶绿素 a 的季节性和高分辨率日深度剖面，评估了这两种机制的作用。两种机制都在水柱中运行，但在不同的季节；硝化作用是夏季分层期间亚硝酸盐积累和冬季混合期间浮游植物亚硝酸盐排泄的主要过程。夏季分层开始时，在透光带下方出现两个氮峰值，即铵最大值 (AM) 和初级亚硝酸盐最大值 (PNM)。两个峰值均位于浮游植物不活跃且不分泌亚硝酸盐的深度范围。在夏季分层期间，水体深层叶绿素最大值（DCM）、AM、PNM 和硝厩啉通过 N 氧化态向下增加进行排序，类似于硝化过程中 N 物质的时间顺序。这种相似性，加上 PNM 的昼夜稳定性及其与 DCM 上方振荡叶绿素分布的共存，与硝化作用作为形成 PNM 的关键过程一致。我们认为传输和反应控制着水柱中 N 物质的垂直顺序和分离。通过简单的箱模型估计氨化、氨氧化、亚硝酸盐氧化和硝酸盐同化的速率常数之比分别为1:3:1.5:0.15。这些现场估计类似于实验室实验中测量的速率常数之间的比率。
Two alternative mechanisms are suggested for nitrite accumulation in the oxy- genated oligotrophic water column: (1) excretion by phytoplankton or (2) microbial oxidation of ammonium (nitrification). This study assessed the role of these 2 mechanisms, based on seasonal and high-resolution diurnal depth profiles of the dissolved inorganic nitrogen (DIN) species (nitrite, ammonium, nitrate) and chlorophyll a in the Gulf of Aqaba, Red Sea. Both mechanisms operated in the water column, but in different seasons; nitrification was the prime process respon- sible for nitrite accumulation during the stratified summer season and phytoplankton nitrite excre- tion operated during winter mixing. At the onset of summer stratification two N peaks developed below the photic zone, an ammonium maximum (AM) and below it the primary nitrite maximum (PNM). Both peaks were located at a depth range where phytoplankton are thought to be inactive and not excreting nitrite. During summer stratification, the water column deep chlorophyll maxi- mum (DCM), AM, PNM and the nitracline were ordered by a downward increase in N oxidation state similar to the temporal order of the N-species during nitrification. This similarity, together with the diurnal stability of the PNM and its co-existence with oscillating chlorophyll profiles above the DCM, is consistent with nitrification as the key process forming the PNM. We suggest that transport and reaction control the vertical order and separation of N-species in the water col- umn. The ratios between the rate constants for ammonification, ammonium oxidation, nitrite oxi- dation and nitrate assimilation were estimated by a simple box model to be 1:3:1.5:0.15, respec- tively. These field estimates are similar to the ratios between the rate constants measured in laboratory experiments.