Model of Microbial Nutrient Uptake

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In 2011, Aksnes and Cao derived a theoretical trait-based model for phytoplankton nutrient uptake, in which inherent microbial traits (cell size, number of porters, handling time, and porter size) are explicitly distinguished from environmental properties (temperature and nutrient concentration with its diffusion coefficient).


The Demonstration plots show the variation in nutrient uptake rate as a function of cell radius, number of porters, and temperature for different ambient nutrient concentrations (controlled by the slider parameter). The results are very different for organisms living in oligotrophic (low nutrient concentration regime) and eutrophic (high nutrient concentration regime) environments.


Contributed by: Elena Beltrán-Heredia (June 2015)
Special thanks to José Carlos Pérez Fuentes
Open content licensed under CC BY-NC-SA



The derivation of the Aksnes and Cao model can be found in [1]. The molecular diffusion and the handling time dependence on temperature can be found in [2] and [3], respectively. The fixed parameter values were chosen according to the references indicated in Table 1 of [1]. However, we used a handling time of 0.03 s at 20 ºC and not 0.12, as in Aksnes and Cao, because of an error in their estimate [4].


[1] D. L. Aksnes and F. J. Cao, "Inherent and Apparent Traits in Microbial Nutrient Uptake," Marine Ecology Progress Series, 440, 2011 pp. 41–51. doi:10.3354/meps09355.

[2] P. A. Jumars, J. W. Deming, P. S. Hill, L. Karp-Boss, P. L. Yager, and W. B. Dade, "Physical Constraints on Marine Osmotrophy in an Optimal Foraging Context," Marine Microbial Food Webs, 7(2): 1993 pp. 121–159.

[3] R. W. Eppley, "Temperature and Phytoplankton Growth in the Sea," Fishery Bulletin, 70(4), 1972 pp. 1063–1085.

[4] Ø. Fiksen, M. J. Follows, and D. L. Aksnes, "Trait-Based Models of Nutrient Uptake in Microbes Extend the Michaelis-Menten Framework," Limnology and Oceanography, 58(1): 2012 pp. 193–202. doi:10.4319/lo.2013.58.1.0193.

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