We study the ocean from the perspective of biogeochemistry - that is, how organisms and materials (studied chemically) interact in earth surface environments. We use concepts and tools of chemistry, geology and biology in these studies. Comparison and coupling of oceanic to terrestrial processes receives special focus.
One major theme is the bioavailability of nutritional and toxic materials. The supply of nutrition to organisms and the exposure to toxins depends on the organisms' ability to remove them from an environmental matrix such as water or sediment. We therefore examine biological capabilities such as digestive physiology of sedimentary animals, which enables design of chemical measurements of that fraction of nutrients or toxins that can be liberated. Integrating nutritional and toxic material studies helps to better understand how organisms become toxified in their search for food. We have studied nutritional bioavailability of proteins and lipids to animals and bacteria. These efforts elucidate behavior at the individual organism scale and community structure and environmental processes, such as bioturbation, at larger scales.
A second theme is studying why some organic matter is NOT available to organisms, with a focus on how the interaction between organic matter and minerals enables preservation and/or burial of organic carbon. This interaction may control organic matter sequestration and hence oxygen accumulation in modern, and perhaps in ancient, times. This work ranges from terrestrial soils to deep-sea sediments, with primary focus on ocean margin environments because of their importance in global carbon cycling. Various surface chemical techniques allow us to better understand how organic matter adsorbs to mineral particles.
A third theme involves the action of light on particulate organic matter. We are finding that the intense sunlight can dissolve significant kinds of particulate organic matter. This process has potentially important implications in areas subjected to such intense light, and may strongly affect oceanic carbon and nutrient cycling. Because light is a limiting factor for these reactions, marine optics becomes an important component of our studies.
Facilities in my lab include HPLC's (with photodiode array UV-VIS and fluorescence detectors), atomic absorption spectrophotometer (graphite furnace, flame and flow injection capability) in a trace metal clean room, X-ray diffractometer, scanning fluorescence spectrometer and UV-VIS spectrophotometer, integrating sphere, surface area and pore size analyzers, dissolved organic carbon/nitrogen analyzer, carbon-nitrogen elemental analyzer, nutrient analyzer, gamma detector for radionuclides, Iatroscan for lipid analysis, microplate reader, microwave digestion equipment, solar simulator, refrigerated supercentrifuge and extensive minor analytical and preparatory equipment.