Ren H, Sigman D M, Meckler A N, Plessen B, Robinson R S, Rosenthal Y, Haug G H
Department of Geosciences, Guyot Hall, Princeton University, Princeton, NJ 08544, USA.
Science. 2009 Jan 9;323(5911):244-8. doi: 10.1126/science.1165787. Epub 2008 Dec 18.
Fixed nitrogen (N) is a limiting nutrient for algae in the low-latitude ocean, and its oceanic inventory may have been higher during ice ages, thus helping to lower atmospheric CO2 during those intervals. In organic matter within planktonic foraminifera shells in Caribbean Sea sediments, we found that the 15N/14N ratio from the last ice age is higher than that from the current interglacial, indicating a higher nitrate 15N/14N ratio in the Caribbean thermocline. This change and other species-specific differences are best explained by less N fixation in the Atlantic during the last ice age. The fixation decrease was most likely a response to a known ice age reduction in ocean N loss, and it would have worked to balance the ocean N budget and to curb ice age-interglacial change in the N inventory.
固定氮（N）是低纬度海洋中藻类生长的限制性营养物质，在冰期时其海洋储量可能更高，从而有助于在这些时期降低大气中的二氧化碳含量。在加勒比海沉积物中浮游有孔虫壳内的有机质中，我们发现末次冰期的15N/14N比值高于当前间冰期，这表明加勒比海温跃层中硝酸盐的15N/14N比值更高。这种变化以及其他物种特异性差异，最好的解释是末次冰期大西洋的固氮作用减少。固氮作用的减少很可能是对已知的冰期海洋氮损失减少的一种反应，它有助于平衡海洋氮收支，并抑制冰期-间冰期氮储量的变化。
