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Metabolism and fate of marine archae...

Shah, Sunita Rajesh.

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Metabolism and fate of marine archaea: Insights from compound-specific radiocarbon analysis.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Metabolism and fate of marine archaea: Insights from compound-specific radiocarbon analysis./
Author:	Shah, Sunita Rajesh.
Description:	175 p.
Notes:	Adviser: Ann Pearson.
Contained By:	Dissertation Abstracts International69-01B.
Subject:	Biogeochemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3295939
ISBN:	9780549409045

Metabolism and fate of marine archaea: Insights from compound-specific radiocarbon analysis.
Shah, Sunita Rajesh.

Metabolism and fate of marine archaea: Insights from compound-specific radiocarbon analysis. - 175 p.

Adviser: Ann Pearson.

Thesis (Ph.D.)--Harvard University, 2008.

In the modern ocean, archaea are found throughout the water column and sediments. Their existence through time is recorded in characteristic isoprenoid membrane lipids, found ubiquitously in sediments deposited over the last 130 million years. In addition to indicating the existence of archaea, these sedimentary lipids contain clues to past marine conditions that are best interpreted with knowledge of the location where they were produced and composition of the archaeal community that produced them. Although it is impossible to know the location and phylogenetic source of lipids preserved in sediments with certainty, progress towards this goal will enable more informed interpretations of the archaeal lipid record. Both understanding the metabolic capabilities of marine archaeal communities, intrinsically linked with community composition, and understanding the source of archaeal tetraether lipids (GDGTs) found in sediments are specific objectives of this thesis. Radiocarbon measurements of archaeal GDGTs from the water column in the North Central Pacific indicate archaeal communities in the mesopelagic ocean are largely autotrophic with a smaller heterotrophic component. It is not known, however, whether there are two separate archaeal groups with distinct carbon metabolisms or one uniformly mixotrophic population. Measurements of the radiocarbon content of sedimentary GDGTs from Santa Monica Basin and Bermuda Rise, two very different settings, indicate multiple sources and mechanisms control the abundance and distribution of GDGTs ultimately preserved. GDGTs are found to be resuspended from surface sediments and laterally transported, but these results also confirm that GDGTs are moderately prone to degradation during this process and are therefore not transported to very distant settings. Contribution of GDGTs from the deep water column or sedimentary archaeal communities appear to be significant to the sediments of Santa Monica Basin. Both of these results can contribute to understanding how archaeal lipids preserved in sediments can be interpreted in the context of past conditions. The most common use of sedimentary GDGTs in a paleoceanographic context is to reconstruct sea surface temperature. These reconstructions suffer from uncertainties regarding the biophysical mechanism and location of the temperature signal's origination. The results presented in this thesis also have implications for TEX86-based paleotemperature reconstructions.

ISBN: 9780549409045Subjects--Topical Terms:

545717
Biogeochemistry.

Metabolism and fate of marine archaea: Insights from compound-specific radiocarbon analysis.
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245 1 0 $a Metabolism and fate of marine archaea: Insights from compound-specific radiocarbon analysis.
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500 $a Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0181.
502 $a Thesis (Ph.D.)--Harvard University, 2008.
520 $a In the modern ocean, archaea are found throughout the water column and sediments. Their existence through time is recorded in characteristic isoprenoid membrane lipids, found ubiquitously in sediments deposited over the last 130 million years. In addition to indicating the existence of archaea, these sedimentary lipids contain clues to past marine conditions that are best interpreted with knowledge of the location where they were produced and composition of the archaeal community that produced them. Although it is impossible to know the location and phylogenetic source of lipids preserved in sediments with certainty, progress towards this goal will enable more informed interpretations of the archaeal lipid record. Both understanding the metabolic capabilities of marine archaeal communities, intrinsically linked with community composition, and understanding the source of archaeal tetraether lipids (GDGTs) found in sediments are specific objectives of this thesis. Radiocarbon measurements of archaeal GDGTs from the water column in the North Central Pacific indicate archaeal communities in the mesopelagic ocean are largely autotrophic with a smaller heterotrophic component. It is not known, however, whether there are two separate archaeal groups with distinct carbon metabolisms or one uniformly mixotrophic population. Measurements of the radiocarbon content of sedimentary GDGTs from Santa Monica Basin and Bermuda Rise, two very different settings, indicate multiple sources and mechanisms control the abundance and distribution of GDGTs ultimately preserved. GDGTs are found to be resuspended from surface sediments and laterally transported, but these results also confirm that GDGTs are moderately prone to degradation during this process and are therefore not transported to very distant settings. Contribution of GDGTs from the deep water column or sedimentary archaeal communities appear to be significant to the sediments of Santa Monica Basin. Both of these results can contribute to understanding how archaeal lipids preserved in sediments can be interpreted in the context of past conditions. The most common use of sedimentary GDGTs in a paleoceanographic context is to reconstruct sea surface temperature. These reconstructions suffer from uncertainties regarding the biophysical mechanism and location of the temperature signal's origination. The results presented in this thesis also have implications for TEX86-based paleotemperature reconstructions.
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