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1 COMPARATIVE BEHAVIOR AND DISTRIBUTION OF BIOLOGICALLY RELEVANT TRACE METALS – IRON, MANGANESE, AND COPPER IN FOUR REPRESENTATIVE OXYGEN DEFICIENT REGIMES OF THE WORLD’S OCEANS by Jagruti Vedamati ________________________________________________________________________ A DISSERTATION Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (OCEAN SCIENCES) August 2013 Copyright 2013 Jagruti Vedamati
|Title||Comparative behavior and distribution of biologically relevant trace metals - iron, manganese, and copper in four representative oxygen deficient regimes of the world's oceans|
|Degree||Doctor of Philosophy|
|Degree program||Ocean Sciences|
|School||College of Letters, Arts And Sciences|
|Advisor (committee chair)||Moffett, James W.|
|Advisor (committee member)||
Capone, Douglas G.
Sanudo-Wilhelmy, Sergio A.
Sañudo-Wilhelmy, Sergio A.
Hammond, Douglas E.
|Abstract||This thesis explores the behavior and distribution of key redox sensitive elements - Fe and Mn under spatially varied suboxic conditions along eastern boundary upwelling regions as compared to that of the non-redox sensitive, bioactive trace metal - Cu. The response of these metals was then analyzed in a different non-oxygen minimum zone (OMZ) setting along Line P to compare and analyze the differences in distribution, if any caused by the suboxic conditions. Fe, Cu and Mn were investigated in the three major OMZs of the world’s oceans -- namely, the eastern tropical south Pacific off the coasts of Peru and Chile, the Arabian Sea and in the Costa Rica Upwelling Dome in eastern tropical north Pacific. For the non-OMZ sampling site, we sampled across a dynamic, high productivity region in the North East sub-arctic Pacific along Line P. ❧ Total dissolved Fe, Cu and Mn concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). Fe (II) concentrations were determined using an automated flow injection analysis system. Results from the Peruvian OMZ indicate that Mn is largely decoupled from Fe. While Fe concentrations were very high on the shelf, it decreased drastically offshore and was coupled to redox conditions. In contrast, Mn concentrations were lower over the shelf and were often higher offshore, especially in surface waters. Results suggest that Mn is efficiently transported away from the highly reducing conditions of the shelf because of slow oxidation kinetics -- in contrast to Fe. In nearshore stations, off the broad continental shelf along the northern and central transects off Peru, exceedingly high Fe were measured with most of the dissolved Fe present as Fe(II) below the oxycline. Along the narrower southern Peruvian shelf, dissolved Fe concentrations were 10-fold lower. ❧ Cu distribution in the OMZs showed some interesting features observed for the first time. In transects through the Arabian Sea OMZ and off of Peru, a distinct draw down in Cu concentrations was observed at mid-depths coincident with the secondary nitrite maximum (SNM) while no such feature was present in stations outside the denitrification zone. Distributions along Line P suggest that one of the most striking differences in Fe & Mn distribution was the presence of high Mn: Fe ratios off the continental shelf along Line P as compared to those obtained in transects off the Peruvian coast. Complex redox cycling of Fe and Mn in the reducing sediments along the continental margin underlying the Peruvian OMZ results in the “Fe trapping” while Mn diffuses off shore into the water column, thereby resulting in lower DMn values along the Peruvian continental shelf. No distinct subsurface Fe plume was present throughout the transect along Line P. Cu depth profiles along Line P exhibit general features of a nutrient like element and agree with previous data from the central North Pacific. However, in the absence of a SNM along Line P, no draw down of Cu was observed at mid-depths similar to Cu distributions within the Arabian Sea OMZ. ❧ Overall, this thesis adds to our understanding of the effect of redox conditions within the suboxic zones on redox sensitive elements – Fe and Mn. It also furthers the knowledge of the behavior and distribution of important, biologically relevant trace metals -Fe, Mn and Cu in the world’s oceans.|
|Keyword||iron; copper; manganese; trace metals; oxygen minimum zones; denitrification|
|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|
|Provenance||Electronically uploaded by the author|
|Legacy record ID||usctheses-m|
|Contributing entity||University of Southern California|
|Physical access||The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given.|
|Repository name||University of Southern California Digital Library|
|Repository address||USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA|
|Contributing entity||University of Southern California|
|Full text||1 COMPARATIVE BEHAVIOR AND DISTRIBUTION OF BIOLOGICALLY RELEVANT TRACE METALS – IRON, MANGANESE, AND COPPER IN FOUR REPRESENTATIVE OXYGEN DEFICIENT REGIMES OF THE WORLD’S OCEANS by Jagruti Vedamati ________________________________________________________________________ A DISSERTATION Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (OCEAN SCIENCES) August 2013 Copyright 2013 Jagruti Vedamati|