The influence of nitrogen speciation on growth and toxicity of Pseudo-nitzschia multiseries and P. pungens in batch and continuous cultures

Anglais

Influence de la spéciation de l'azote sur la croissance et la toxicité de Pseudo-nitzschia multiseries et P. pungens en cultures en batch ou en continu

Calu Guillaume (1) ; Martin-Jezequel Véronique (2) ; Lefaux Estelle (2) ; Sechet Véronique (1) ; Lassus Patrick (1) ; Weigel Pierre (2) ; Amzil Zouher (1)

(1) Ifremer (France) ; (2) université de Nantes (France)

The amount of urea used as fertilizer in agriculture has tripled over the last four last decades. This nutrient is discharged in large quantities from rivers to coastal waters, and is used as food by many microalgae. Previous studies have shown that numerous toxic species can assimilate both organic and inorganic nitrogen. This has also been proposed by some researchers as a potential cause of the increased occurrence of some diatom species of the genus Pseudo-nitzschia that produce domoic acid, a neurotoxin that can contaminate shellfish. Moreover, higher domoic acid content has been reported for P. australis in the presence of urea. We investigated the influence of urea on the content of domoic acid in P. multiseries and P. pungens. Our results showed that, in batch cultures, P. multiseries contains more toxin per cell in the presence of urea. In continuous cultures, substitution of nitrates by urea increases the cellular toxin content of P. pungens. These findings suggest the importance of nitrogen speciation in domoic acid production by certain species of Pseudo-nitzschia.

acide domoïque ; pseudo-nitzschia ; nitrates ; urée

domoic acid ; pseudo-nitzschia ; nitrate ; urea

2009

7 p.

5. Harmful phytoplankton