Coupled nitrogen and oxygen isotope fractionation of nitrate during assimilation by cultures of marine phytoplankton
Coupled nitrogen and oxygen isotope fractionation of nitrate during assimilation by cultures of marine phytoplankton
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DOI：
10.4319/lo.2004.49.5.1763
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发表时间：
2004-09-01
影响因子：
4.5
通讯作者：
Harrison, PJ
中科院分区：
文献类型：
--
作者：
Granger, J;Sigman, DM;Harrison, PJ
本文首次测量了海洋浮游植物在实验室培养过程中对硝酸盐（NO3-）的氮(N)和氧(O)耦合同位素变化，并推导了三种硅藻（weissflogii， thalassisira oceanica和thalassisira pseudonana）和一种球石藻（Emiliana huxleyi）对硝酸盐同化的N和O动力学同位素效应。N同位素效应在种间和种内存在较大差异。与硝酸盐消耗相关的O同位素效应与N同位素效应一致，因此，无论物种或同位素效应的大小，硝酸盐的O-18/O-16和N-15/N-14的变化比例近似为1:1。此外，不同环境条件下生长的魏氏滴虫体内硝酸盐的O-18/O-16和N-15/N-14相对于培养基硝酸盐呈1:1的比例升高。这些发现与以硝酸还原为主要分馏步骤的硝酸盐同位素分馏机制相一致。在硝酸盐同化过程中观测到的N:O同位素耦合表明，水柱硝酸盐的N和O同位素联合测量可以为海洋N循环提供新的约束。
We report the first measurements of coupled nitrogen (N) and oxygen (O) isotopic variations of nitrate (NO3-) during its assimilation by laboratory cultures of marine phytoplankton and derive the N and O kinetic isotope effects for nitrate assimilation by three species of diatoms (Thalassiosira weissflogii, Thalassiosira oceanica, and Thalassiosira pseudonana) and a coccolithophorid (Emiliana huxleyi). Large interspecies and intraspecies variations in the N isotope effects were observed. The O isotope effect associated with nitrate consumption was consistently close to the N isotope effect, such that the O-18/O-16 and N-15/N-14 of nitrate varied in a ratio of similar to1:1, regardless of species or of the magnitude of the isotope effect. In addition, the O-18/O-16 and N-15/N-14 of internal nitrate of T. weissflogii grown under various environmental conditions were elevated relative to the medium nitrate by a proportion of similar to1: 1. These findings are consistent with a nitrate isotopic fractionation mechanism that involves nitrate reduction as the chief fractionating step. The observed N:O isotopic coupling during nitrate assimilation suggests that combined N and O isotopic measurements of water column nitrate can provide new constraints on the ocean N cycle.