My research interests are focused on the development of new analytical methods for chemicals in seawater and application of these tools to studies of chemical cycling throughout the ocean. Our main interest today is developing chemical sensors that can be deployed on profiling floats. Sensors include nitrate and pH. We have developed a variety of analytical methods for metals present at ultratrace concentrations in seawater using flow injection analysis with chemiluminescence and fluorescence detection. These methods have been used in a variety of studies of metal cycling in the ocean. Analytical methods for iron, an essential micronutrient, have been used in the IRONEX experiment to map iron as it was added in the equatorial Pacific and to study iron in coastal ecosystems. Methods sensitive to metal speciation have been used to study copper complexation in polluted harbors and to study the physical chemistry of metal oxidation. Over the past 15 years, we have also developed a variety of sensors and analyzers that operate in situ to depths of 4000 m. These instruments have been used to study processes ranging from the distribution of sulfide in deep-sea hydrothermal vent systems to nitrate in coastal ponds surrounded by intensive agricultural activities.