Diatom-bound 15N/14N: New support for enhanced nutrient consumption in the ice age subantarctic
Diatom-bound 15N/14N: New support for enhanced nutrient consumption in the ice age subantarctic
复制标题
硅藻结合的 15N/14N：冰河时代亚南极地区营养消耗增加的新支持
DOI：
10.1029/2004pa001114
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
D. Lea
中科院分区：
文献类型：
--
作者：
R. Robinson;D. Sigman;P. DiFiore;M. M. Rohde;T. Mashiotta;D. Lea
[1]利用硅藻结合态15 N/14 N值重建了南大洋亚南极带的冰川营养状态。来自太平洋和印度地区的岩芯记录显示，末次盛冰期δ 15 N为5 - 6‰，随着冰川终止，δ 15 N值下降至2‰。无论是硅藻组合或生理变化的影响，对藻类结合的15 N/14 N是未知的，还不能排除作为一个可能的解释所观察到的变化。然而，印度和太平洋部门的记录和其他古海洋学数据之间的一致性表明，冰川-间冰期的差异，在南极绑定的15 N/14 N是由较高的消耗硝酸盐在亚南极表面在最后一个冰河时期。这种营养物质消耗的变化可能是由于大气铁施肥和/或与海冰融化相关的冰川混合层深度减少。在冰川亚南极洲的营养消耗增加将有助于降低冰河时代大气中的二氧化碳浓度。它也会减少低纬度温跃层中预先形成的营养物质含量，导致低纬度生产力、亚低氧和反硝化作用的下降。
[1] Diatom-bound 15N/14N was used to reconstruct the glacial nutrient status of the Subantarctic Zone in the Southern Ocean. Down-core records from both the Pacific and Indian sectors show δ15N of 5 to 6‰ during the Last Glacial Maximum and a decrease, coincident with the glacial termination, to values as low as 2‰. The effect of either diatom assemblage or physiological change on the diatom-bound 15N/14N is unknown and cannot yet be ruled out as a possible explanation for the observed change. However, the consistency between Indian and Pacific sector records and with other paleoceanographic data suggests that the glacial-interglacial difference in diatom-bound 15N/14N was driven by higher consumption of nitrate in the subantarctic surface during the last ice age. Such a change in nutrient consumption may have resulted from atmospheric iron fertilization and/or decreased glacial mixed layer depths associated with sea ice melting. Enhanced nutrient consumption in the glacial subantarctic would have worked to lower the concentration of CO2 in the ice age atmosphere. It also would have reduced the preformed nutrient content of the low-latitude thermocline, leading to decreases in low-latitude productivity, suboxia, and denitrification.