||Loureiro Sofia1, Jauzein Cecile2, Garces Esther1, Collos Yves2, Camp Jordi1, Vaque Dolors1
||1 : Inst Ciencias Mar, Dept Biol Marina Oceanog 1, ICM CSIC, Barcelona 08003, Catalonia, Spain.
2 : Univ Montpellier 2, CNRS, IFREMER, Lab Ecosyst Lagunaires UMR 5119,CC093, F-34095 Montpellier 5, France.
||Journal of plankton research (0142-7873) (Oxford university press), 2009-04 , Vol. 31 , N. 4 , P. 399-410
|WOS© Times Cited
||Harmful Algal Blooms (HABs), Nitrogen Uptake, Urea, Dissolved Organic Matter (DOM)
||The influence of organic nutrients on the evolution of Pseudo-nitzschia delicatissima cultures was investigated in an enrichment experiment with high-molecular-weight dissolved organic matter (HMWDOM) and in an uptake assay with N-15-ammonium and N-15-urea. HMWDOM was extracted from seawater collected at a nearby shore station during the decline of a diatom bloom. Four incubations were prepared: L1/5+DOM (P. delicatissima grown in L1 growth medium with 1/5 of the nitrate concentration of standard L1), (L1-N)+DOM (L1 without nitrate, i.e. nitrogen-deficient treatment), L1-DOM (control culture without added DOM) and BV+DOM (bacterial and viral control, free of microalgae). Incubations were carried out for 10 days. Chlorophyll a concentrations differed after day 4 and reached higher levels in the L1-DOM incubation by the end of the experiment; however, similar growth rates were observed in all incubations (1.64 +/- 0.05 divisions day(-1)). The persistently lower cellular chlorophyll content in (L1-N)+DOM during the experiment was consistent with N limitation conditions. The data suggested that the nitrogen needed for the growth of (L1-N)+DOM cells might have originated from the DOM. Based on the results of N-15 uptake assays, it was concluded that P. delicatissima more readily acquires ammonium than urea. Nevertheless, under low N conditions, P. delicatissima may use urea as an alternative N source, and comparable photosynthetic rates are attained on either substrate. Taken together, our results suggest a positive effect of organic nutrients on the growth of P. delicatissima.