||Jauzein Cecile1, 2, Collos Yves1, Laabir Mohamed1, Vaquer Andre1
||1 : Univ Montpellier 2, CNRS, IRD, Lab Ecol Syst Marins Cotiers,UMR 5119, F-34095 Montpellier 5, France.
2 : IFREMER, Lab LER LR, F-34203 Sete, France.
||Harmful Algae (1568-9883) (Elsevier Science Bv), 2011-11 , Vol. 11 , P. 73-80
|WOS© Times Cited
||Diel cycle, Dark uptake, Nitrogen, Carbon, Uncoupling, Alexandrium catenella
||Uptake rates of three potential N-sources (ammonium, nitrate and N-urea) and two potential C-sources (HCO(3)(-) and C-urea) were estimated during growth of Alexandrium catenella in both light and dark phases. According to the variations observed in (13)C-isotopic ratio, A. catenella cells were not able to use C-urea. Furthermore, decreases in (13)C cell content during darkness revealed a probably high involvement of C recently fixed in dark respiration. Dark N-uptake capacities of A. catenella were characterized by dark/light uptake ratio of 27%, 43% and 65% for NO(3)(-), NH(4)(+) and N-urea, respectively. An accumulation of C-rich compounds during the light period was highlighted through strong diel variations in C:N ratio and would provide C and energy for these dark uptake processes indicating an uncoupling between N and C metabolism. Total costs in terms of C associated with dark N-uptake and assimilation were estimated and revealed that the main part of those costs may be associated with maintenance metabolism in A. catenella cells. The relatively low C-costs of biosynthesis in darkness suggest that dark uptake and C-storage strategies correspond to a benefit in terms of competitiveness for A. catenella, optimized by the migrating abilities of this species. (C) 2011 Elsevier B.V. All rights reserved.
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|Author's final draft