Foraminiferal isotope evidence of reduced nitrogen fixation in the ice age Atlantic ocean

H. Ren, Daniel Mikhail Sigman, A. N. Meckler, B. Plessen, R. S. Robinson, Y. Rosenthal, G. H. Haug

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131 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)244-248
Number of pages5
Issue number5911
StatePublished - Jan 9 2009

All Science Journal Classification (ASJC) codes

  • General


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