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Development and paleoceanographic ap...

Ren, Haojia.

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Development and paleoceanographic application of planktonic foraminifera-bound nitrogen isotopes.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Development and paleoceanographic application of planktonic foraminifera-bound nitrogen isotopes./
Author:	Ren, Haojia.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2010,
Description:	248 p.
Notes:	Source: Dissertations Abstracts International, Volume: 72-07, Section: B.
Contained By:	Dissertations Abstracts International72-07B.
Subject:	Chemical Oceanography. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3437783
ISBN:	9781124394978

Development and paleoceanographic application of planktonic foraminifera-bound nitrogen isotopes.
Ren, Haojia.

Development and paleoceanographic application of planktonic foraminifera-bound nitrogen isotopes. - Ann Arbor : ProQuest Dissertations & Theses, 2010 - 248 p.

Source: Dissertations Abstracts International, Volume: 72-07, Section: B.

Thesis (Ph.D.)--Princeton University, 2010.

This item must not be sold to any third party vendors.

Biologically available nitrogen ("fixed N") is the proximately limiting nutrient in much of today's ocean. The input/output budget has been argued to control the fertility of the ocean and the ocean's role in setting atmospheric CO2. The two stable isotopes of N (14N and 15N) and their fractionation by natural processes provide a mechanism for studying the budget of oceanic fixed N in the past. However, outside of sedimentary environments characterized by high organic matter preservation, bulk sedimentary N is subjected to diagenetic alteration and contamination with allochthonous N and thus cannot be used reliably to reconstruct past N isotope changes. In the search for reliable archives, this dissertation describes the first method for isotopic analysis of planktonic foraminiferal shell-bound N, which has its basis in the very high sensitivity of the "denitrifier method" for N isotope analysis. Isotopic measurements of foraminifera biomass from Sargasso Sea net tow material and of shell-bound N from Cariaco Basin sediment traps and from shallow sediments collected in different open ocean regions show a strong correlation between foraminifera-bound δ 15N (FB-δ15N) and changes in the subsurface nitrate δ 15N, which is the dominant source of new N to the euphotic zone. The isotopic difference among multiple species of foraminifera with different depth habitats and behaviors offers insight into the biological controls on FB-δ15N and also speaks to the potential richness of this paleoceanographic tool. This dissertation has resulted in the first evidence for reduced N fixation in the oligotrophic open oceans during the last glacial maximum (LGM). Down core studies from the Caribbean Sea and the South China Sea both show higher FB-δ15N during the last ice age than the current interglacial. This is best explained by a reduction in N fixation rate during the last ice age in both ocean basins, with or without assumption of constant mean ocean nitrate δ15N. These data, when compared with reconstructions of ice age denitrification, provides perhaps the strongest direct evidence to date for the longstanding hypothesis of a feedback between denitrification and N fixation across the global ocean that stabilizes the size of the ocean N reservoir.

ISBN: 9781124394978Subjects--Topical Terms:

1674678
Chemical Oceanography.
Subjects--Index Terms:

Denitrification

Development and paleoceanographic application of planktonic foraminifera-bound nitrogen isotopes.
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300 $a 248 p.
500 $a Source: Dissertations Abstracts International, Volume: 72-07, Section: B.
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500 $a Advisor: Sigman, Daniel M.
502 $a Thesis (Ph.D.)--Princeton University, 2010.
506 $a This item must not be sold to any third party vendors.
520 $a Biologically available nitrogen ("fixed N") is the proximately limiting nutrient in much of today's ocean. The input/output budget has been argued to control the fertility of the ocean and the ocean's role in setting atmospheric CO2. The two stable isotopes of N (14N and 15N) and their fractionation by natural processes provide a mechanism for studying the budget of oceanic fixed N in the past. However, outside of sedimentary environments characterized by high organic matter preservation, bulk sedimentary N is subjected to diagenetic alteration and contamination with allochthonous N and thus cannot be used reliably to reconstruct past N isotope changes. In the search for reliable archives, this dissertation describes the first method for isotopic analysis of planktonic foraminiferal shell-bound N, which has its basis in the very high sensitivity of the "denitrifier method" for N isotope analysis. Isotopic measurements of foraminifera biomass from Sargasso Sea net tow material and of shell-bound N from Cariaco Basin sediment traps and from shallow sediments collected in different open ocean regions show a strong correlation between foraminifera-bound δ 15N (FB-δ15N) and changes in the subsurface nitrate δ 15N, which is the dominant source of new N to the euphotic zone. The isotopic difference among multiple species of foraminifera with different depth habitats and behaviors offers insight into the biological controls on FB-δ15N and also speaks to the potential richness of this paleoceanographic tool. This dissertation has resulted in the first evidence for reduced N fixation in the oligotrophic open oceans during the last glacial maximum (LGM). Down core studies from the Caribbean Sea and the South China Sea both show higher FB-δ15N during the last ice age than the current interglacial. This is best explained by a reduction in N fixation rate during the last ice age in both ocean basins, with or without assumption of constant mean ocean nitrate δ15N. These data, when compared with reconstructions of ice age denitrification, provides perhaps the strongest direct evidence to date for the longstanding hypothesis of a feedback between denitrification and N fixation across the global ocean that stabilizes the size of the ocean N reservoir.
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650 4 $a Geochemistry. $3 539092
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653 $a Nitrogen fixation
653 $a Nitrogen isotopes
653 $a Planktonic foraminifera
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