DISSERTATION RESEARCH: An Ecophysiological Approach to Understanding Macroalgal Nitrate Metabolism and Photosynthesis

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DISSERTATION RESEARCH: An Ecophysiological Approach to Understanding Nitrate Metabolism and PhotosynthesisTimothy Sherman and Julien LartigueAll plants and especially aquatic plants are subject to temporal variation in the availability of nutrients and light. As a consequence, many plants appear to have evolved a capacity to regulate their metabolism in response to these fluctuations. How plants tune their photosynthetic and nutrient assimilation pathways to the ambient conditions and integrate these two fundamental processes is the focus of this research. Three cosmopolitan genera of macroalgae - Enteromorpha (Chlorophyta), Gracilaria (Rhodophyta), and Gelidium (Rhodophyta) - will serve as the plant models for this work. The goals of this research are 1) to understand how non-synchronous fluctuations in light and nitrate availability influence nitrate metabolism and 2) to develop a model for predicting rates of nitrate reduction in the field. The fate of nitrate, from uptake to assimilation, will be tracked using the stable isotope, N15, while pulse amplitude modulated (PAM) fluorometry will allow for repeated, non-invasive sampling of photosynthetic pathways. This integrative approach will lead to a linking of the physiology of nitrate metabolism and photosynthesis in the context of a plant's physical and chemical surroundings. The result will be a more complete picture of macroalgal physiology at the level of the whole organism. This work also seeks to integrate research with undergraduate education by including aspects of this research in a marine botany course.