Danielle Greenhow (2006). Seas In-situ Spectrophotometric Phosphate Profiling in the Gulf of Mexico
Facility Advisor: David Hastings

ABSTRACT

In oligotrophic waters, biogeochemical cycling exerts a dominant influence on phosphate concentrations within the euphotic zone. Due to extensive nutrient scavenging by phytoplankton in the upper water column, near-surface phosphate concentrations are often lower than the detection limits of traditional analytical techniques. Conventional discrete sampling methods result in nutrient profiles that are limited to an average of twelve points spanning the upper 100 meters. The spectrophotometric elemental analysis system (SEAS) describe in this thesis is an in-situ, continuous flow instrument capable of a 0.5 Hz sampling frequency. A liquid core waveguide is used to achieve nanomolar detection levels. SEAS colorimetric analysis of phosphate with a molybdenum blue method allows for easy, rapid, open-ocean profiling as well as analysis in other aquatic ecosystems.