AUTHOR=Moisan Tiffany A. , Mitchell B. Greg 

TITLE=Modeling Net Growth of Phaeocystis antarctica Based on Physiological and Optical Responses to Light and Temperature Co-limitation

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 4 - 2017

YEAR=2018

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2017.00437

DOI=10.3389/fmars.2017.00437

ISSN=2296-7745

ABSTRACT=Temperature and light are fundamental environmental variables which regulate phytoplankton growth rates when nutrients are in excess.  For polar coastal oceans that are undergoing changes in sea ice cover and warming, light and temperature are particularly important for bloom dynamics.  Using colonial Phaeocystis antarctica cultures grown at steady-state, we assessed the combined effect of these two environmental controls on net growth rate (n), chlorophyll-specific absorption of light (a*ph ()), and quantum yields for growth ().  Specific net growth rates (n) varied from 0.04 to 0.34 day-1 within a matrix of light and temperature ranging from 14 to 542 mol quanta m-2 s-1 and –1.5 to 4C.  Values of a*ph () varied significantly with light but only slightly with temperature.  Values of  ranged from 0.003 to 0.09 mol C (mol quanta absorbed)-1 with highest values at low light and 4oC.  For excess irradiances or low temperatures where growth rate is inhibited, quantum yields were low.  The low μ values are attributed both to increased absorption by photoprotective pigments compared to photosynthetic pigments and thermodynamic control of dark reaction enzymes.  The systematic changes in photophysiological properties of P. antarctica in relation to temperature and light were used to develop a series of nested light- and temperature-dependent models for n, a*ph (), and .  A model for a*ph (300-700 nm) was developed that takes into account the systematic changes in a*ph () due to pigment packaging effects and cellular concentrations of chlorophylls and photoprotective pigments.  Also, a model for  was developed based on a cumulative one-hit Poisson probability function.  These model parameterizations for absorption and quantum yield are combined into an overall model of net growth that can be applied easily to Phaeocystis antarctica bloom dynamics using remote sensing data for temperature, light, and chlorophyll a.  Furthermore modeling based on the biophysical variables a*ph (), and  that are shown to regulate the growth rate provides a more fundamental mechanistic approach compared to other modeling methods that do not explicitly resolve photon flux into the cell or the quantum yield.