Co-limitation of diatoms by iron and silicic acid in the equatorial Pacific
Co-limitation of diatoms by iron and silicic acid in the equatorial Pacific
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DOI：
10.1016/j.dsr2.2010.08.005
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发表时间：
2011-02-01
影响因子：
3
通讯作者：
Twining, Benjamin S.
中科院分区：
文献类型：
--
作者：
Brzezinski, Mark A.;Baines, Stephen B.;Twining, Benjamin S.
在110 ° W和140 ° W经度之间进行了一系列为期两年的9个微宇宙实验，研究了硅（Si）和铁（Fe）作为赤道东太平洋（EEP）限制性营养盐的相对作用。Si和Fe的添加量始终不同，但协同效应对常量营养元素的使用，浮游植物生物量和浮游植物群落结构。硅除了增加草酸的使用和生物硅的生产，但没有显着的影响，使用无机氮或正磷酸盐，叶绿素积累，颗粒无机（PIC）碳积累，或浮游生物群落组成相对于控制。这一结果，连同观察到的Si添加增加了细胞硅含量的数字占主导地位的硅藻由类似的50%，表明硅的主要影响是调节硅藻硅化。与Si的作用一样，Fe的加入增加了草酸的利用率和生物硅的产量，而对PIC的产量没有影响。与硅的影响不同，铁的加入也提高了有机质的生产率，对硅藻细胞硅含量没有影响，并导致最初罕见的，大（> 40 μ m）硅藻相对于对照组的增长，表明铁限制主要是通过其对生长速度和浮游植物群落组成的影响。一个羽状硅藻属Pseudo-nitzschia占主导地位的硅藻组合在原地，在控制很容易增长，并没有表现出强烈的增长反应，无论是铁或硅此外，这表明其增长受到其他因素，如放牧或光。此外，锗，硅藻细胞分裂的抑制剂，消除了铁对常量营养素的使用，生物硅生产和叶绿素积累和浮游植物群落组成的影响，符合主要硅藻响应铁此外。缺乏对铁的PIC生产的反应表明，颗石藻没有铁限制。同时添加Fe和Si，通过Fe对大型硅藻生长的促进作用，使营养盐下降和生物量积累达到最大水平。结果表明，一种形式的共同限制与硅调节硅藻硅化和生物硅生产的速度，而铁调节有机物质的生产，通过限制浮游植物的生长速度，特别是那些大型硅藻。结果反对硅调节EEP平均上升流条件下的新生产。铁的添加是必要的，足以刺激完全去除硝酸盐的赤道上升流区表明，新的生产受到限制，低环境溶解铁与结果一致，从原位铁施肥实验进行赤道以南的赤道上升流区以外。(C)2010爱思唯尔有限公司保留所有权利。
The relative roles of silicon (Si) and iron (Fe) as limiting nutrients in the eastern equatorial Pacific (EEP) were examined in a series of nine microcosm experiments conducted over two years between 110 degrees W and 140 degrees W longitude. Si and Fe additions had consistently different but synergistic effects on macronutrient use, phytoplankton biomass and phytoplankton community structure. Silicon addition increased silicic acid use and biogenic silica production, but had no significant effect on the use of inorganic nitrogen or orthophosphate, chlorophyll accumulation, particulate inorganic (PIC) carbon accumulation, or plankton community composition relative to controls. That result, together with observations that Si addition increased the cellular Si content of the numerically dominant diatom by similar to 50%, indicates that the main effect of Si was to regulate diatom silicification. Like the effect of Si, Fe addition increased the rate of silicic acid use and biogenic silica production and had no effect on PIC production. Unlike the effect of Si, Fe addition also enhanced rates of organic matter production, had no effect on cellular Si content of diatoms, and resulted in the growth of initially rare, large (> 40 mu m) diatoms relative to controls, indicating that Fe limitation acts mainly through its effects on growth rate and phytoplankton community composition. A pennate diatom of the genus Pseudo-nitzschia dominated the diatom assemblage in situ, grew readily in the controls and did not show a strong growth response to either Fe or Si addition suggesting that its growth was regulated by other factors such as grazing or light. Addition of germanium, an inhibitor of diatom cell division, eliminated the effects of Fe on macronutrient use, biogenic silica production and chlorophyll accumulation and phytoplankton community composition, consistent with a predominantly diatom response to Fe addition. The lack of a response of PIC production to Fe suggests that coccolithophores were not Fe limited. Addition of Fe and Si together resulted in the greatest levels of nutrient drawdown and biomass accumulation through the effect of Fe in promoting the growth of large diatoms. The results suggest a form of co-limitation with Si regulating diatom silicification and the rate of biogenic silica production while Fe regulates the production of organic matter through limitation of phytoplankton growth rates, in particular those of large diatoms. The results argue against Si regulation of new production in the EEP under average upwelling conditions. Iron addition was necessary and sufficient to stimulate complete removal of nitrate within the equatorial upwelling zone suggesting that new production was restricted by low ambient dissolved Fe consistent with results from in situ Fe fertilization experiments conducted to the south of the equator outside of the equatorial upwelling zone. (C) 2010 Elsevier Ltd. All rights reserved.