Exploring a first principle-based model for Zooplankton Metabolism (EXZOME)

Zooplankton metabolism strongly impacts pH changes as well as carbon and nitrogen fluxes in the ocean and these impacts influence the role of the ocean in modulating CO2 buildup in the atmosphere and climate change.  Zooplankton metabolism has many components, both anabolic and catabolic; this proposal is concerned with the components of respiration and ammonium excretion.  Its objective is to test a new mechanistic model of zooplankton metabolism (Packard and Gomez, in press) by using it to predict respiration and ammonium excretion in both well-fed and starved zooplankton. The model is based on the understanding that respiratory oxygen utilization in zooplankton is caused by enzyme-catalyzed redox reactions in the respiratory electron transport system (ETS) and that the physiological rate of ammonium excretion is caused by the NH4+ producing reaction catalyzed by glutamate-dehydrogenase. Here we argue that this ETS-based model can be used to predict zooplankton respiratory oxygen consumption. An important aspect of this model is its use of Michaelis-Menten kinetics to express the substrate dependence of the enzyme activities between their maximal and minimal velocities.  By testing this model we will be testing all the algorithms and assumptions upon which it is based.