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Calcification rate in Emiliania huxleyi Lohmann in response to light, nitrate and availability of inorganic carbon.

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Bibliographic Details
Title: Calcification rate in Emiliania huxleyi Lohmann in response to light, nitrate and availability of inorganic carbon.
Authors: Nimer, N. A.1, Merrett, M. J.1
Source: New Phytologist. Apr93, Vol. 123 Issue 4, p673-677. 5p.
Subjects: Coccolithus huxleyi, Nitrates, Carbon, Photosynthesis, Photons, Stoichiometry, Calcification
Abstract: The relationship between photosynthesis and calcification was investigated in a high-calcifying strain of Emiliania huxleyi. At pH 8.3 and a photon flux density of 50 μmol m-2 s-1 calcification and photosynthetic 14CO2 fixation were carbon saturated at 1 mM DIC (dissolved inorganic carbon) but at a photon flux density μmol m-2 s-1 calcification and photosynthetic 14CO2 fixation were not saturated at the DIC concentration of sea-water, 2 mM. When HCO3- provides the bulk of inorganic carbon the stoichiometry between photosynthetic 14CO2 fixation and calcification was 1:1. In the high-calcifying strain of E. huxleyi the stoichiometry between photosynthetic 14CO2 fixation and O2 evolution was 2:1 but in a low calcifying strain the stoichiometry was 1:1. High nitrate concentrations, i.e. 1000 μM were required to inhibit calcification. The optimum pH for calcification and photosynthetic 14CO2 fixation was 7.8. From the results a model is proposed in which a molecule of HCO3- is the precursor of calcite in the coccolith vesicle with the extrusion of H+ into the cytosol, while another HCO3- provides CO2 in the chloroplast with the extrusion of OH-. The interaction of these processes maintains cytoplasmic pH near neutrality. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The relationship between photosynthesis and calcification was investigated in a high-calcifying strain of <em>Emiliania huxleyi</em>. At pH 8.3 and a photon flux density of 50 μmol m-2 s-1 calcification and photosynthetic 14CO2 fixation were carbon saturated at 1 mM DIC (dissolved inorganic carbon) but at a photon flux density μmol m-2 s-1 calcification and photosynthetic 14CO2 fixation were not saturated at the DIC concentration of sea-water, 2 mM. When HCO3- provides the bulk of inorganic carbon the stoichiometry between photosynthetic 14CO2 fixation and calcification was 1:1. In the high-calcifying strain of <em>E. huxleyi</em> the stoichiometry between photosynthetic 14CO2 fixation and O2 evolution was 2:1 but in a low calcifying strain the stoichiometry was 1:1. High nitrate concentrations, i.e. 1000 μM were required to inhibit calcification. The optimum pH for calcification and photosynthetic 14CO2 fixation was 7.8. From the results a model is proposed in which a molecule of HCO3- is the precursor of calcite in the coccolith vesicle with the extrusion of H+ into the cytosol, while another HCO3- provides CO2 in the chloroplast with the extrusion of OH-. The interaction of these processes maintains cytoplasmic pH near neutrality. [ABSTRACT FROM AUTHOR]
ISSN:0028646X
DOI:10.1111/j.1469-8137.1993.tb03776.x