Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean
Enhanced carbon pump inferred from relaxation of nutrient limitation in the glacial ocean
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DOI：
10.1038/nature08101
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发表时间：
2009-06
期刊：
影响因子：
64.8
通讯作者：
L. Pichevin;B. Reynolds;R. Ganeshram;I. Cacho;L. Pena;K. Keefe;R. Ellam
中科院分区：
文献类型：
--
作者：
L. Pichevin;B. Reynolds;R. Ganeshram;I. Cacho;L. Pena;K. Keefe;R. Ellam
现代东赤道太平洋（EEP）是大气碳的一个重要海洋来源。EEP大面积地区的初级生产力受到磷酸和铁的限制，由于这一限制，向深海输出的有机碳无法补偿深海沃茨上涌释放的二氧化碳。有人认为，将尘埃携带的铁输送到冰川海洋，可能增加了该地区的初级生产力，增加了深海碳输出，降低了冰川期大气中的二氧化碳浓度。EEP的这种作用得到了下面的冰川沉积物中记录的较高有机碳埋藏率的支持，但较低的蛋白石积累率对EEP作为海洋区域的重要性产生了怀疑。在这里，我们提出了一个新的硅同位素记录，表明蛋白石的积累率在冰川EEP的矛盾下降的结果，硅碳吸收比硅藻的条件下，铁的可用性增加，从增强灰尘输入的减少。因此，我们的研究支持了在末次冰期该地区的一个生物泵的想法，这可能有助于冰川二氧化碳下降。此外，利用硅和氮同位素变化的证据，我们推断，在现代情况下，在该地区的生物生产力是不受限制的铁，硅和氮在冰期的可用性。我们假设，一个浓缩的生物二氧化碳泵的限制，也许只有磷的限制是一个更常见的发生在低纬度地区的冰川海洋。
The modern Eastern Equatorial Pacific (EEP) Ocean is a large oceanic source of carbon to the atmosphere. Primary productivity over large areas of the EEP is limited by silicic acid and iron availability, and because of this constraint the organic carbon export to the deep ocean is unable to compensate for the outgassing of carbon dioxide that occurs through upwelling of deep waters. It has been suggested that the delivery of dust-borne iron to the glacial ocean,could have increased primary productivity and enhanced deep-sea carbon export in this region, lowering atmospheric carbon dioxide concentrations during glacial periods. Such a role for the EEP is supported by higher organic carbon burial rates documented in underlying glacial sediments,, but lower opal accumulation rates cast doubts on the importance of the EEP as an oceanic region for significant glacial carbon dioxide drawdown,. Here we present a new silicon isotope record that suggests the paradoxical decline in opal accumulation rate in the glacial EEP results from a decrease in the silicon to carbon uptake ratio of diatoms under conditions of increased iron availability from enhanced dust input. Consequently, our study supports the idea of an invigorated biological pump in this region during the last glacial period that could have contributed to glacial carbon dioxide drawdown. Additionally, using evidence from silicon and nitrogen isotope changes, we infer that, in contrast to the modern situation, the biological productivity in this region is not constrained by the availability of iron, silicon and nitrogen during the glacial period. We hypothesize that an invigorated biological carbon dioxide pump constrained perhaps only by phosphorus limitation was a more common occurrence in low-latitude areas of the glacial ocean.