Eastߞwest gradients in the photosynthetic potential of phytoplankton and iron concentration in the subarctic Pacific Ocean during early summer
Eastߞwest gradients in the photosynthetic potential of phytoplankton and iron concentration in the subarctic Pacific Ocean during early summer
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DOI：
10.4319/lo.2002.47.6.1581
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发表时间：
2002-11
影响因子：
4.5
通讯作者：
Koji Suzuki;Hongbin Liu;T. Saino;H. Obata;Michiaki Takano;K. Okamura;Y. Sohrin;Yukiyo Fujishima
中科院分区：
文献类型：
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作者：
Koji Suzuki;Hongbin Liu;T. Saino;H. Obata;Michiaki Takano;K. Okamura;Y. Sohrin;Yukiyo Fujishima
1999年初夏，在亚北极太平洋及其邻近沃茨，利用快速重复频率荧光计连续测定了表层浮游植物光系统II的光化学量子产额（Fv/Fm）和功能吸收截面（PSII）。还在每个采样站测定了总可溶性铁（TD-Fe）的浓度。Fv/Fm的最大值（0.61）出现在阿留申半岛外，那里的TD-Fe浓度相对较高。西亚北极环流（WSG）和阿拉斯加环流（AG），分别位于西北和东北亚北极太平洋，是在高营养，低叶绿素（HNLC）的条件。表面TD-Fe通常保留在WSG中，但在AG中耗尽（<0.01 nmol L−1）。夜间Fv/Fm值和PSII值分别显著高于（p < 0.01）和低于（p < 0.01）AG。铁或氮的限制通常会导致Fv/Fm的降低和PSII的增加。这些结果表明，有一个东西梯度（WSG。AG）在亚北极太平洋浮游植物光合能力中的差异，这种差异可能是由海水中的铁含量引起的。事实上，我们在AG中进行的铁富集实验显示，在添加0.8 nmol L−1铁后，Fv/Fm从0.27增加到0.49，而α PSII从496 x 10 − 20 m2光子−1减少到365 x 10−20 m2光子−1。与此同时，一个戏剧性的植物区系的转变，从植物鞭毛虫硅藻被发现的色素签名。铁对整个亚北极太平洋浮游植物的光合生理起主要控制作用。
In the subarctic Pacific and its adjacent waters, the photochemical quantum yield (Fv/Fm) and the functional absorption cross section (ΣPSII) of photosystem II for surface phytoplankton were continuously measured during the early summer of 1999 using a fast repetition rate fluorometer. Concentrations of total dissolvable iron (TD‐Fe) were also determined at each sampling station. The maximum value (0.61) of Fv/Fm was observed off the Aleutian Peninsula, where TD‐Fe concentrations were relatively high. The Western Subarctic Gyre (WSG) and the Alaskan Gyre (AG), located in the northwest and northeast subarctic Pacific, respectively, were in high‐nutrient, low‐chlorophyll (HNLC) conditions. Surface TD‐Fe generally remained in the WSG but was depleted (<0.01 nmol L−1) in the AG. Nighttime Fv/Fm and ΣPSII in the WSG were significantly higher (p < 0.01) and lower (p < 0.01), respectively, than in the AG. Iron or nitrogen limitations generally lead to a decrease in Fv/Fm and an increase in ΣPSII. These results suggested that there was an east‐west gradient (WSG . AG) in the photosynthetic competence of phytoplankton in the subarctic Pacific and that the difference was probably caused by iron levels in seawater. Indeed, our iron enrichment experiment in the AG revealed that Fv/Fm increased from 0.27 to 0.49 and ΣPSII decreased from 496 x 10−20 to 365 x 10−20 m2 photon−1 after a 0.8 nmol L−1 iron addition. At the same time, a dramatic floristic shift from phytoflagellates to diatoms was found by pigment signatures. Iron could principally control the photosynthetic physiology of phytoplankton in the whole subarctic Pacific.