The Interactive Effects of Light & Nutrient Source on the Molecular Regulation of Nitrogen Assimilation, Photochemistry, & Growth of Two Raphidophyte Species from DE's Inla

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Understanding the environmental and biological factors that contribute to phytoplankton population dynamics is a central goal in the study of aquatic ecology. Although much is known about how individual variables such as nitrogen and light impact phytoplankton, little is known about the interactive effects of these parameters. The utilization of nitrate, in particular, is largely controlled by the amount of light absorbed. Nitrate reductase, an enzyme involved in assimilating nitrate, has also been shown to prevent damage to photosynthesis by siphoning off excess light energy during periods of intense sunlight. Two harmful algal species, Heterosigma akashiwo and Chattonella subsalsa, often bloom in Delaware's inland bays. They make excellent subjects for investigating the interactive effects of nutrients and light, as they both bloom during periods of high light exposure yet prefer different sources of nitrogen. For this project, rates of nitrogen uptake will be determined at different light levels for each species. The roles of light, temperature and nutrient availability in the regulation of nitrate reductase will be examined, and the impact of nitrate reductase and other biochemical pathways on photosynthesis will be evaluated. This research will examine links between carbon and nitrogen utilization at multiple levels, from expression of carbon- and nitrogen- regulated genes, to photobiology, to shifts in natural algal communities. Results of this work will contribute to the development of ecological models of harmful algal bloom development and a better characterization of the primary factors that impact phytoplankton ecology. This research will directly involve the training and education of graduate and undergraduate students. Dissemination of research results to the public is planned through both print and lecture presentations and an interactive website targeting middle and high school students.