Graduation Year

2005

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Marine Science

Major Professor

Kent A. Fanning, Ph.D.

Committee Member

Steven Hendrix, Ph.D.

Committee Member

Gabriel Vargo, Ph.D.

Committee Member

John Walsh, Ph.D.

Committee Member

Richard Gilbert, Ph.D.

Keywords

Chemical, Oceanography, Submersible, Analyzer, Sensor, Auv

Abstract

The overall focus of this research was to achieve the first detailed understanding of temporal and geographical distributions of inorganic-nitrogen-nutrients within an oligotrophic euphotic zone. In addition to low supply of nutrients, the uptake of nutrients by phytoplankton within the euphotic zone draws the nutrient concentrations down, resulting in very low concentrations of these nutrients and results in these regions being classified as oligotrophic. The site selected for the research was the West Florida Shelf (WFS). There were two main challenges. One was that the detection limits of the standard chemistries used to determine inorganic nitrogen nutrients are not low enough to permit the evaluation of the concentration of these nutrients within an oligotrophic euphotic zone. The other challenge was the adaptation and design of highly sensitive, robust, and simple instrumentation to resolve and evaluate horizontal nutrient distributions within the euphotic zone for both ship-based and Autonomous Underwater Vehicle (AUV) based platforms in near real time.

With these obstacles in mind three major goals were set. First was the development of a simple and robust chemistry that could detect nitrite and nitrate with a suitably low detection limit (approximately 10 nanomolar) and could also be coupled with a highly sensitive chemistry previously developed for ammonium with the same characteristics, and incorporate these chemistries into a single laboratory analyzer designed to monitor the surface distribution of these nutrients in the water sampled with a ships flow-through system.

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