Regional impacts of iron-light colimitation in a global biogeochemical model
Regional impacts of iron-light colimitation in a global biogeochemical model
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DOI：
10.5194/bg-7-1043-2010
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发表时间：
2010-01-01
期刊：
影响因子：
4.9
通讯作者：
Hiscock, M. R.
中科院分区：
文献类型：
--
作者：
Galbraith, E. D.;Gnanadesikan, A.;Hiscock, M. R.
实验室和野外研究表明，铁在浮游植物生理学中具有多种作用，对捕光细胞机制特别重要。然而，尽管铁限制被明确地包括在许多地球化学/生态系统模型中，但其实施方式各不相同，并且其对光捕获效率的影响常常被忽视。鉴于海洋环境的复杂性，很难预测采用不同的铁限制计划的后果。在这里，我们探讨了铁和营养循环的相互作用，在海洋环流模式使用一个新的，流线型的海洋地球化学模型。建立在以前公布的参数化的光适应和出口生产，生物地球化学与轻铁营养素和气体（BLING）模型构建只有四个明确的示踪剂，但包括常量营养素和微量营养素的限制，光限制，和隐式处理的社区结构。这种计算成本低廉的模型结构简单，使我们能够清楚地隔离铁的可用性对最大光饱和光合速率的全球影响与铁对光合效率的影响。我们发现，光饱和光合速率的影响是占主导地位的，否定了光合效率的重要性，在大多数地区，特别是寒冷的南大洋沃茨。这种情况的主要例外发生在北方半球富含铁的地区，在那里，高光饱和光合速率允许光合效率发挥更重要的作用。换句话说，在光饱和增长率低的地区，有效收集光子的能力几乎没有影响。此外，我们推测，浮游植物细胞占主导地位的铁有限的地区往往有相对较高的光合效率，由于减少包装的影响。如果这一推测是正确的，这将意味着铁胁迫浮游植物的自然群落可能倾向于更有效地收获光子比从铁限制实验与其他浮游植物。我们认为，铁限制光合效率有一个相对较小的影响全球海洋地球化学，虽然它预计会影响浮游生物的季节性循环以及初级生产力的垂直结构。
Laboratory and field studies have revealed that iron has multiple roles in phytoplankton physiology, with particular importance for light-harvesting cellular machinery. However, although iron-limitation is explicitly included in numerous biogeochemical/ecosystem models, its implementation varies, and its effect on the efficiency of light harvesting is often ignored. Given the complexity of the ocean environment, it is difficult to predict the consequences of applying different iron limitation schemes. Here we explore the interaction of iron and nutrient cycles in an ocean general circulation model using a new, streamlined model of ocean biogeochemistry. Building on previously published parameterizations of photoadaptation and export production, the Biogeochemistry with Light Iron Nutrients and Gasses (BLING) model is constructed with only four explicit tracers but including macronutrient and micronutrient limitation, light limitation, and an implicit treatment of community structure. The structural simplicity of this computationally-inexpensive model allows us to clearly isolate the global effect that iron availability has on maximum light-saturated photosynthesis rates vs. the effect iron has on photosynthetic efficiency. We find that the effect on light-saturated photosynthesis rates is dominant, negating the importance of photosynthetic efficiency in most regions, especially the cold waters of the Southern Ocean. The primary exceptions to this occur in iron-rich regions of the Northern Hemisphere, where high light-saturated photosynthesis rates allow photosynthetic efficiency to play a more important role. In other words, the ability to efficiently harvest photons has little effect in regions where light-saturated growth rates are low. Additionally, we speculate that the phytoplankton cells dominating iron-limited regions tend to have relatively high photosynthetic efficiency, due to reduced packaging effects. If this speculation is correct, it would imply that natural communities of iron-stressed phytoplankton may tend to harvest photons more efficiently than would be inferred from iron-limitation experiments with other phytoplankton. We suggest that iron limitation of photosynthetic efficiency has a relatively small impact on global biogeochemistry, though it is expected to impact the seasonal cycle of plankton as well as the vertical structure of primary production.