Diffusion and Low Light Effects on the Nutrition and Growth of Large Marine Diatoms

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9416012 Goldman PROJECT ABSTRACT The proposed research will investigate the importance of uncoupling photosynthetic carbon incorporation and nitrate uptake under low light conditions. Low light conditions are common at the base of the euphotic zone where episodic inputs of nutrients through mixing events might trigger the rapid growth of large diatoms. In addition, studies will be performed on the role that diffusion may play in the limitation of nitrate uptake and hence diatom growth. Those same experiments will also investigate the possibility that diatom growth might become limited by free CO2 as the pH rises and the total inorganic carbon pool shrinks. These studies will be performed in a series of controlled laboratory experiments involving isolates of large diatoms form the Sargasso Sea that are currently in culture in the Principal Investigator's laboratory. The results will provide a basis for assessing important aspects of the physiology of large phytoplankton species, their role in new production, and the potential impact of molecular diffusion in structuring the autotrophic portion of marine food chains.