Estimates of specific toxicity in several Pseudo-nitzschia species from the Washington coast, based on culture and field studies
AbstractTo gain an understanding of the species of Pseudonitzschia
that are the major toxin producers in the Pacific Northwest, representative isolates from the Ecology and Oceanography of Harmful Algal Blooms in
the Pacific Northwest (ECOHAB-PNW) study site were grown as clonal cultures. Both particulate and dissolved domoic acid (DA) were measured at various stages of growth using a receptor-binding assay and an
enzyme-linked immunosorbent assay respectively, and compared to toxin data obtained during a cruise in September 2003. A clonal P. multiseries culture isolated from a northern beach site contained the highest particulate DA (pDA) level of 70.4nmol l–1 and released the
highest amount of dissolved DA (dDA, >5nmol l–1), illustrating
the potential for this species to cause harm. A clonal P. australis isolate also produced relatively high levels of pDA (3.2nmol l–1) and dDA (4.3nmol l–1), whereas P. delicatissima, P. cf. pseudodelicatissima, P.
pungens and P. fraudulenta produced low or undetectable
levels of pDA and dDA. These culture studies suggest that the dDA levels of up to 17.6nmol l–1 measured during September 2003 were owing to toxin produced and released primarily by P. australis cells. It
is estimated that the maximum specific toxicity reached by P. australis at a toxic ‘hot spot’ off the Washington coast in mid-September 2003 was 94.4pg cell–1.