Control of domoic acid toxin expression in Pseudo-nitzschia multiseries by copper and silica: relevance to mussel aquaculture in New England (USA).

The production of the toxin Domoic Acid (DA) by the diatoms Pseudo-nitzschia spp. is affected by several environmental factors, among them copper and silica. The effects of these nutrients upon DA production have been studied individually, but not in combination. There is evidence, however, that in diatoms copper can enter the cell via the silicic-acid transport site. The goal of this study was to analyze the effect of the interaction between copper and silicic-acid supply upon DA production in Pseudo-nitzschia multiseries. The study was motivated by concerns about the risk of toxigenic Pseudo-nitzschia spp. impacting mussel aquaculture in New England (USA). The results of the present study do not indicate that copper uses the silicic acid transport site to enter the cell; nevertheless, there is an interaction between these two nutrients that produces a synergistic affect upon toxin production. A small increase in copper, without a simultaneous increase in silicate, as well as an increase in both copper and silicate, leads to DA up-regulation. Furthermore, the field component of this study reports the presence of species of Pseudo-nitzschia on the New England coast that are capable of producing DA. Together these findings indicate that risk of DA impacting mussel aquaculture along the coast of New England would be increased by an unusual enrichment of copper in the vicinity of mussel farms.