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Thursday, February 16, 2012
2:00 PM - 2:45 PM
CNLS Conference Room (TA-3, Bldg 1690)

Postdoc Seminar

A Dynamic Model of Flexible Phytoplankton Nutrient Uptake

Michael Raghib
T-5 and CNLS

The metabolic machinery of marine microbes can be remarkably plastic, allowing organisms to persist under extreme nutrient limitation. With a few exceptions, most theoretical approaches to nutrient uptake in phytoplankton are largely dominated by the classic Michaelis Menten (MM) uptake functional form, whose constant parameters cannot account for the observed plasticity in the uptake apparatus. Here, we propose a simple cell level model based on a dynamic view of the uptake process whereby the cell can regulate the synthesis of uptake proteins in response to changes in both the internal and external nutrient concentrations. In our flexible approach, the maximum uptake rate and nutrient affinity increase monotonically as the external nutrient concentration decreases. For low to medium nutrient availability, our model predicts uptake and growth rates larger than the classic MM counterparts, while matching the classic MM results for large nutrient concentrations. These results have important consequences for global coupled models of ocean circulation and biogeochemistry, which lack this regulatory mechanism and are thus likely to underestimate phytoplankton abundances and growth rates in nutrient-poor regions of the ocean.

Host: Kipton Barros, T-4 and CNLS