↑ Recent research has uncovered a gene encoding an iron storage protein (ferritin) in several species of Pseudo-nitzschia [ 90 ]. Together with the finding that domoic acid (DA) can complex trace metals such as iron and copper [ 89, 91 ], this may help to explain their success in HNLC regions. Ferritin is a common molecule in many organisms, but its presence in diatoms had not previously been detected. Preliminary results suggest that the gene for ferritin may be confined to only a small subset of diatoms that includes the HA genus Pseudo-nitzschia [ 90 ]. Pseudo-nitzschia commonly occur along coastlines and are responsible for closures of shellfish and finfish harvests due to accumulation of DA in the tissues of commercially and recreationally important marine species. Very few open ocean Pseudo-nitzschia species have been isolated into culture. Even fewer isolates have been tested for DA production, thus far with negative results, indicating that either Pseudo-nitzschia species from HNLC ocean environments produce little or no DA or that the unique culture conditions required to elicit toxin production were not met [ 92 ]. Given the success of Pseudo-nitzschia species in iron enrichment experiments, it is important to investigate further their potential to produce toxin to better evaluate the consequences of proposed large-scale ocean fertilization to mitigate increasing atmospheric carbon [ 92 ].
