MEPS 434:29-43 (2011)  -  DOI:

Phytoplankton growth allometry and size dependent C:N stoichiometry revealed by a variable quota model

Zhi-Ping Mei1,3,*, Zoe V. Finkel2, Andrew J. Irwin1

1Department of Math & Computer Science, Mount Allison University, Sackville, New Brunswick E4L 1E6, Canada
2Environmental Science Program, Mount Allison University, Sackville, New Brunswick E4L 1A5, Canada
3Present address: University of Maryland Center for Environmental Science, Horn Point Laboratory, PO Box 775, Cambridge, Maryland 21613, USA

ABSTRACT: Size scaling of phytoplankton growth rates and size-dependent carbon to nitrogen (C:N) stoichiometry determine phytoplankton size structure and coupling of carbon and nitrogen cycling of marine ecosystems. They are critical in predicting the growth of phytoplankton spanning a wide range of sizes and their consequences for the biological pump in marine ecosystem models. The size scaling of phytoplankton growth and size-dependent C:N stoichiometry are modelled by embedding size-dependent light-harvesting, nutrient acquisition and storage into Droop’s quota-dependent phytoplankton growth model. The size-scaling exponent of maximum growth rate of phytoplankton is –0.17 (which is higher than the universal size-scaling exponent of –1⁄4 predicted by the metabolic theory of ecology) under saturated light and NO3. The size-scaling exponent of growth rate (μ) decreases with increasing light under saturated NO3, and decreases with decreasing NO3 concentration under saturated light. The allometry of equilibrium cellular C and N quota varies with light and NO3 concentrations. Under saturated light and NO3 concentration, C:N increases slightly with cell size. Under limiting light, but saturated NO3, C:N is close to the Redfield ratio and is not size dependent. Under limiting NO3 but saturated light, C:N is higher than the Redfield ratio and increases with cell size. We identified the uncertainty of the size-scaling exponent of μ associated with key parameters, for which more data need to be collected in the lab and field.

KEY WORDS: Phytoplankton growth · Size scaling · Community structure · C:N · Transport network · Quota

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Cite this article as: Mei ZP, Finkel ZV, Irwin AJ (2011) Phytoplankton growth allometry and size dependent C:N stoichiometry revealed by a variable quota model. Mar Ecol Prog Ser 434:29-43.

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