Monday, December 7, 2009

Domoic Acid

If phytoplankton capable of making DA are common in open ocean phytoplankton blooms, do they express this gene and make DA? There have been few measurements published related to the expression of the gene for DA in open ocean phytoplankton. Wells and coworkers [Wells et al., 2005] are one of the few groups who have studied Pseudonitzschia in the open ocean. They indicate that DA plays an important role, together with copper, in ensuring that Pseudonitzschia can survive under very low iron conditions in the open ocean. “This system may explain why Pseudonitzschia spp. are persistent seed populations in oceanic HNLC regions, as well as in some neritic regions. Our findings also indicate that in the absence of an adequate copper supply, iron-limited natural Pseudonitzschia populations will become increasingly toxic.” (p. 1998). We know from studies of Pseudonitzschia strains from coastal waters that they are more likely to make DA when iron-stressed than when growing under iron-replete conditions: “Our findings suggest that DA production during exponential growth of these two toxigenic Pseudonitzschia species is directly induced by Fe-deficient or Cu stress conditions and that 95% of this DA is actively released into the medium.” (p.
515) [Maldonado et al., 2002].

Nualgi contains both Iron and Copper

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