Watson A J, Bakker D C, Ridgwell A J, Boyd P W, Law C S
School of Environmental Sciences, University of East Anglia, Norwich, UK.
Nature. 2000 Oct 12;407(6805):730-3. doi: 10.1038/35037561.
Photosynthesis by marine phytoplankton in the Southern Ocean, and the associated uptake of carbon, is thought to be currently limited by the availability of iron. One implication of this limitation is that a larger iron supply to the region in glacial times could have stimulated algal photosynthesis, leading to lower concentrations of atmospheric CO2. Similarly, it has been proposed that artificial iron fertilization of the oceans might increase future carbon sequestration. Here we report data from a whole-ecosystem test of the iron-limitation hypothesis in the Southern Ocean, which show that surface uptake of atmospheric CO2 and uptake ratios of silica to carbon by phytoplankton were strongly influenced by nanomolar increases of iron concentration. We use these results to inform a model of global carbon and ocean nutrients, forced with atmospheric iron fluxes to the region derived from the Vostok ice-core dust record. During glacial periods, predicted magnitudes and timings of atmospheric CO2 changes match ice-core records well. At glacial terminations, the model suggests that forcing of Southern Ocean biota by iron caused the initial approximately 40 p.p.m. of glacial-interglacial CO2 change, but other mechanisms must have accounted for the remaining 40 p.p.m. increase. The experiment also confirms that modest sequestration of atmospheric CO2 by artificial additions of iron to the Southern Ocean is in principle possible, although the period and geographical extent over which sequestration would be effective remain poorly known.
南大洋中海洋浮游植物的光合作用以及相关的碳吸收，目前被认为受铁的可利用性限制。这种限制的一个影响是，在冰川时期向该地区提供更多的铁可能会刺激藻类光合作用，从而导致大气中二氧化碳浓度降低。同样，有人提出向海洋人工添加铁可能会增加未来的碳固存。在此，我们报告了一项关于南大洋铁限制假说的全生态系统测试数据，这些数据表明，大气中二氧化碳的表层吸收以及浮游植物对硅与碳的吸收比率，受到铁浓度纳摩尔级增加的强烈影响。我们利用这些结果为一个全球碳和海洋养分模型提供信息，该模型由源自沃斯托克冰芯尘埃记录的该地区大气铁通量驱动。在冰川期，预测的大气二氧化碳变化幅度和时间与冰芯记录吻合良好。在冰川期末期，该模型表明，铁对南大洋生物群的作用导致了冰川 - 间冰期二氧化碳变化最初约40 ppm，但其他机制必定导致了其余40 ppm的增加。该实验还证实，原则上通过向南大洋人工添加铁来适度固存大气中的二氧化碳是可能的，尽管固存有效的时期和地理范围仍知之甚少。
