Uptake of dissolved inorganic and organic nitrogen by the benthic toxic dinoflagellate Ostreopsis cf. ovata

Type Article
Date 2017-05
Language English
Author(s) Jauzein Cecile1, 2, Couet Douglas1, Blasco Thierry1, Lemee Rodolphe1
Affiliation(s) 1 : UPMC Univ Paris 06, Sorbonne Univ, INSU CNRS, Lab Oceanog Villefranche, Villefranche Sur Mer, France.
2 : IFREMER, Ctr Brest, DYNECO PELAGOS, F-29280 Plouzane, France.
Source Harmful Algae (1568-9883) (Elsevier Science Bv), 2017-05 , Vol. 65 , P. 9-18
DOI 10.1016/j.hal.2017.04.005
WOS© Times Cited 27
Keyword(s) Uptake, Nitrogen, Dinoflagellate, Ostreopsis, Kinetics, Interactions

Environmental factors that shape dynamics of benthic toxic blooms are largely unknown. In particular, for the toxic dinoflagellate Ostreopsis cf. ovata, the importance of the availability of nutrients and the contribution of the inorganic and organic pools to growth need to be quantified in marine coastal environments. The present study aimed at characterizing N-uptake of dissolved inorganic and organic sources by O. cf. ovata cells, using the 15N-labelling technique. Experiments were conducted taking into account potential interactions between nutrient uptake systems as well as variations with the diel cycle. Uptake abilities of O. cf. ovata were parameterized for ammonium (NH4+), nitrate (NO3−) and N-urea, from the estimation of kinetic and inhibition parameters. In the range of 0 to 10 μmol N L−1, kinetic curves showed a clear preference pattern following the ranking NH4+ > NO3− > N-urea, where the preferential uptake of NH4+ relative to NO3− was accentuated by an inhibitory effect of NH4+ concentration on NO3− uptake capabilities. Conversely, under high nutrient concentrations, the preference for NH4+ relative to NO3− was largely reduced, probably because of the existence of a low-affinity high capacity inducible NO3− uptake system. Ability to take up nutrients in darkness could not be defined as a competitive advantage for O. cf. ovata. Species competitiveness can also be defined from nutrient uptake kinetic parameters. A strong affinity for NH4+ was observed for O. cf. ovata cells that may partly explain the success of this toxic species during the summer season in the Bay of Villefranche-sur-mer (France).

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