The relative availability of inorganic carbon and inorganic nitrogen influences the response of the dinoflagellate Protoceratium reticulatum to elevated CO2.
This work originates from three facts: (i) changes in CO2availability influence metabolic processes in algal cells; (ii) Spatial and temporal variations of nitrogen availability cause repercussions on phytoplankton physiology; (iii) Growth and cell composition are dependent on the stoichiometry of nutritional resources. In this study, we assess whether the impact of rising pCO2is influenced by N availability, through the impact that it would have on the C/N stoichiometry, in conditions of N sufficiency. Our experiments used the dinoflagellate Protoceratium reticulatum, which we cultured under three CO2regimes (400, 1,000, and 5,000 ppmv, pH of 8.1) and either variable (the NO3-concentration was always 2.5 mmol · L-1) or constant (NO3-concentration varied to maintain the same Ci/NO3-ratio at all pCO2) Ci/NO3-ratio. Regardless of N availability, cells had higher specific growth rates, but lower cell dry weight and C and N quotas, at elevated CO2. The carbohydrate pool size and the C/N was unaltered in all treatments. The lipid content only decreased at high pCO2at constant Ci/NO3-ratio. In the variable Ci/NO3-conditions, the relative abundance of Rubisco (and other proteins) also changed; this did not occur at constant Ci/NO3-. Thus, the biomass quality of P. reticulatum for grazers was affected by the Ci/NO3-ratio in the environment and not only by the pCO2, both with respect to the size of the main organic pools and the composition of the expressed proteome.
Laboratorio di Fisiologia delle Alghe e delle Piante, Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, Ancona, 60131, Italy.
Mattia
M
Pierangelini
Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.|Functional Plant Biology and Climate Change Cluster (C3), University of Technology Sydney, Ultimo, NSW, 2007, Australia.
John A
JA
Raven
Laboratorio di Fisiologia delle Alghe e delle Piante, Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, Ancona, 60131, Italy.|Institute of Microbiology, Academy of Sciences of the Czech Republic, Trěboň, 379 01, Czech Republic.|Institute of Marine Science, National Research Council, Arsenale Castello, 2737/F, 30122, Venezia, Italy.|Istituto di Biologia Agro-Ambientale e Forestale, National Research Council, Via G. Marconi n. 2, Porano, 05010, Terni, Italy.
Mario
M
Giordano
D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D004141:Dinoflagellida / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000378:metabolism*
D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen

CO
2
; cell composition; dinoflagellate; elemental stoichiometry; global change