JPR Advance Access originally published online on September 8, 2009
Journal of Plankton Research 2009 31(11):1363-1372; doi:10.1093/plankt/fbp080
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Effect of marine autotrophic dissolved organic matter (DOM) on Alexandrium catenella in semi-continuous cultures
1 Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CSIC. Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalonia, Spain 2 Université Montpellier II, CNRS, Ifremer, Laboratoire Ecosystèmes Lagunaires (UMR 5119), CC093, 34095 Montpellier, Cedex 5, France
* CORRESPONDING AUTHOR: esther{at}icm.csic.es
Received on May 19, 2009; accepted on August 12, 2009
| Abstract |
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Alexandrium catenella was grown in semi-continuous cultures in L1 growth-medium enriched with concentrated dissolved organic matter (DOM) from a diatom bloom. In medium with full nitrate (880 µM), the average growth rate was 0.32 ± 0.01 day–1 (L1, control without added DOM). Adding natural marine dissolved organic nitrogen (DON) at levels of 20–30 µM above background (10 µM) led to a higher growth rate (L1+DOM, 0.40 ± 0.00 day–1). In medium with lower nitrate level (175 µM) and higher DON (L1/5+DOM treatment), both dissolved inorganic nitrogen and DON were used, leading to the highest growth rates (0.43 ± 0.03 day–1). In medium without nitrate [(L1-N)+DOM treatment], the low ammonium concentrations observed throughout the experiment (<1 µM) as well as the uptake kinetics of A. catenella could not have supported the observed growth rates, leading us to conclude that DON was directly used by this organism, rather than using N remineralized by bacteria (from DON). The decrease of bacteria in DOM enriched bioassays could point to a nutrient limitation and competition with A. catenella for organic matter. Viruses likely contributed as an additional factor to keep the bacterial population from becoming dominant.
Corresponding editor: William Li