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PHOTOPHYSIOLOGICAL PARAMETERS FOR CO2 AND N2 FIXATION OF
TRICHODESMIUM SPP. IN NATURAL POPULATIONS AND IN CULTURE
NUTRIENT LIMITATION EXPERIMENTS
by
Juliette Anne Finzi
____________________________________________________________________
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(OCEAN SCIENCES)
August 2007
Copyright 2007 Juliette Anne Finzi
Object Description
| Title | Photophysiological parameters for CO2 and N2 fixation in trichodesmium spp. in natural populations and culture nutrient limitation experiments |
| Author | Finzi, Juliette Anne |
| Author email | finzi@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Ocean Sciences |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2006-08-28 |
| Date submitted | 2007 |
| Restricted until | Unrestricted |
| Date published | 2007-08-06 |
| Advisor (committee chair) | Capone, Douglas |
| Advisor (committee member) |
Hammond, Doug Subramaniam, Ajit Keifer, Dale Michaels, Tony |
| Abstract | Trichodesmium is a globally significant cyanobacterium that plays an important role in marine carbon (C) and nitrogen (N) cycling. Accordingly, global ecosystem have begun to incorporate the critical role of diazotrophs, and Trichodesmium specifically. Most commonly, this is done by incorporating the photophysiological parameters Pmax (the rate at which production is maximal) and alpha; (the linear relationship between production and light at low irradiance), which are derived from production vs. irradiance (P-E) curves. Results of experiments in which Pmax andalpha; for CO2 and N2 fixation by Trichodesmium were measured in the tropical N. Atlantic and tropical N. Pacific are presented. Pmax and alpha; for CO2 fixation were not significantly different between basins, but they were reduced in the Atlantic compared to the Pacific for N2 fixation. It is hypothesized that differences in light history and nutritional status contribute to these basin differences. Additionally, laboratory culture experiments were conducted to elucidate the effect of phosphorus (P) and iron (Fe) limitation on Pmax and alpha; for CO2 and N2 fixation. All parameters were both reduced under nutrient limiting conditions. Finally, Trichodesmium is capable of fixing both CO2 and N2 concurrently throughout the day, but it does not contain heterocysts. Nitrogenase, the key enzyme in N2 fixation, is inhibited by the presence of O2 - a significant by-product from photosynthesis. Therefore, it still remains unclear how these two functions co-occur. Hypotheses indicate that there may be spatial and temporal segregation of the two processes. Using nanometer resolution secondary ion mass spectrometry (nanoSIMS), uptake of 15N and 13C through N2 and CO2 fixation, were traced and measured throughout individual cells along a Trichodesmium trichome at multiple time points throughout the day.; CO2 fixation rates were maximal in the morning, while N2 fixation rates were maximal in the early afternoon indicating that there is indeed a temporal segregation between CO2 and N2 fixation. It could not be determined if there is also a spatial segregation of the two processes. |
| Keyword | trichodesmium; photophysiology; N2 fixation; CO2 fixation; Fe limitation; P limitation; nanoSIMS |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m758 |
| Rights | Finzi, Juliette Anne |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Finzi-20070806 |
| Archival file | uscthesesreloadpub_Volume44/etd-Finzi-20070806.pdf |
Description
| Title | Page 1 |
| Full text | PHOTOPHYSIOLOGICAL PARAMETERS FOR CO2 AND N2 FIXATION OF TRICHODESMIUM SPP. IN NATURAL POPULATIONS AND IN CULTURE NUTRIENT LIMITATION EXPERIMENTS by Juliette Anne Finzi ____________________________________________________________________ A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (OCEAN SCIENCES) August 2007 Copyright 2007 Juliette Anne Finzi |
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