On the interannual variability of nitrogen fixation in the subtropical gyres
On the interannual variability of nitrogen fixation in the subtropical gyres
复制标题
副热带环流固氮的年际变化
DOI：
10.1357/002224009788597944
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发表时间：
2009
影响因子：
0.5
通讯作者：
M. Follows
中科院分区：
文献类型：
--
作者：
F. Monteiro;M. Follows
对北部亚热带环流中的化学示踪剂和重氮生物丰度的时间序列观察表明，在年际和更长的时间尺度上，固氮作用是不同的。利用一个高度理想化的副热带环流生物地球化学和生态学模型，我们探索了之前提出的假设，即这种变异性由内部的“生物地球化学振荡器”调节。我们发现，在某些参数范围内，固氮、群落结构和生物地球化学循环中存在自我维持的振荡，即使在完全稳定的物理强迫下也是如此。在固氮的振荡过程中，重氮菌的“水华”发生在一年到几十年之间，这与观察到的变异性一致。振荡的周期受温跃层水和混合层水之间的交换率的强烈调节。振荡解出现在一个相对较小的参数空间区域，但重氮菌和非重氮菌的相对适合度很接近，每类浮游植物的时间平均生物量都是最大的。
Time-series observations of geochemical tracers and diazotroph abundances in the northern subtropical gyres suggest variability in nitrogen fixation on interannual and longer timescales. Using a highly idealized model of the biogeochemistry and ecology of a subtropical gyre, we explore the previously proposed hypothesis that such variability is regulated by an internal “biogeochemical oscillator.” We find, in certain parameter regimes, self-sustained oscillations in nitrogen fixation, community structure and biogeochemical cycles even with perfectly steady physical forcing. During the oscillations of nitrogen fixation, “blooms” of diazotrophs occur at intervals between a year and several decades, consistent with the observed variability. The period of the oscillations is strongly regulated by the exchange rate between the thermocline and mixed-layer waters. The oscillatory solutions occur in a relatively small region of parameter space, but one in which the relative fitness of diazotrophs and non-diazotrophs are closely matched and the time-averaged biomass of each class of phytoplankton is maximized.