Occurrence, Toxicity, and Diversity of \u3ci\u3ePseudo-nitzschia\u3c/i\u3e in Florida Coastal Waters

Domoic acid (DA), a potent neurotoxin that has the potential to cause amnesic shellfish poisoning (ASP), is produced by members of the marine diatom genus Pseudo-nitzschia. Outbreaks of ASP in humans and of DA poisoning in birds and marine mammals have been reported across the United States and Canada since the late 1980\u27s. Pseudo-nitzschia species can be extremely abundant in Florida waters, with densities often exceeding 106 cells/L, and sometimes exceeding 107 cells/L. Based on preliminary data, it is evident that at least nine species of Pseudo-nitzschia are found in Florida coastal waters. At least six of these species are known to produce DA in other parts of the world, and some are morphologically identical to some of the major toxin-producing species in Californian and Canadian waters. Despite the strong presence of Pseudo-nitzschia, there has never been a report of ASP or a DA-related animal mortality event from Florida. Data collected from 2004 to 2011 show maximum Pseudo-nitzschia abundances exceeded 4 x 107 cells/L. Six species of Pseudo-nitzschia were identified from central west and southwest Florida waters via light and electron microscopy. This is the first report of P. micropora from the Gulf of Mexico. Additionally P. calliantha, P. cuspidata, and P. pungens were identified as producers of DA in Florida coastal waters; although cell quotas of DA were low. Low levels of DA were detected in about one third of the water samples analyzed and DA concentrations measured in the majority of shellfish from the study area were at least an order of magnitude below the regulatory limit of 20 µg/g, suggesting that Pseudo-nitzschia currently poses little threat to human health in Florida. However, DA production in Pseudo-nitzschia species has been shown to be variable and dependent on nutrient conditions, indicating that the potential for DA-related events to occur in Florida warrants further investigation