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

TitleModeling Net Growth of Phaeocystis antarctica Based on Physiological and Optical Responses to Light and Temperature Co-limitation
Publication TypeJournal Article
Year of Publication2018
AuthorsMoisan T.A, Mitchell B.G
JournalFrontiers in Marine Science
Date Published2019/02
Type of ArticleArticle
Accession NumberWOS:000456917300001
Keywordsabsorption; belgian coastal waters; carbon; cell-size; co-limitation; Environmental Sciences & Ecology; environmental-factors; Marine & Freshwater Biology; modeling; Phaeocystis; photophysiology; photosynthesis; phytoplankton; phytoplankton growth; quantum yield; ross sea; steady-state description

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 (mu(n)), chlorophyll-specific absorption of light (a(ph)* (lambda)), and quantum yields for growth (phi(mu)). Specific net growth rates (mu(n)) varied from 0.04 to 0.34 day(-1 )within a matrix of light and temperature ranging from 14 to 542 mu mol quanta m(-2)s(-1) and -1.5 to 4 degrees C. Values of a(ph)* (lambda) varied significantly with light but only slightly with temperature. Values of phi(mu), ranged from 0.003 to 0.09 mol C (mol quanta absorbed)(-1) with highest values at low light and 4 degrees C. For excess irradiances or low temperatures where growth rate is inhibited, quantum yields were low. The low phi(mu), 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 mu(n), a(ph)* (lambda), and phi(mu). A model for a(ph)* (lambda) (300-700 nm) was developed that takes into account the systematic changes in a(ph)* (lambda) due to pigment packaging effects and cellular concentrations of chlorophylls and photoprotective pigments. Also, a model for phi(mu) was developed based on a cumulative one-hit Poisson probability function. These model parameterization for absorption and quantum yield are combined into an overall model of net growth that can be applied easily to P antarctica bloom dynamics using remote sensing data for temperature, light, and chlorophyll a. Furthermore, modeling based on the biophysical variables a(ph)* (lambda) and phi(mu), 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.

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