Smith SL, Yamanaka Y, Pahlow M, Oschlies A

Optimal uptake kinetics: physiological acclimation explains the pattern of nitrate uptake by phytoplankton in the ocean

Despite the lack of any firm theoretical basis for its application, the Michaelis-Menten (MM) equation has remained the basis for modeling nutrient uptake by phytoplankton (and other organisms) for decades. Typically applied using a fixed half-saturation constant, the MM equation effectively assumes a fixed physiology for nutrient uptake, with no acclimation in response to changing nutrient concentrations. Optimal Uptake (OU) kinetics allows for such acclimation and agrees with results from laboratory experiments that MM kinetics fails to describe. In agreement with observations covering broad areas of the ocean, OU predicts that half-saturation concentration should increase as the square root of nutrient concentration, and thus improves the representation of biological production in global ocean models.

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