The 2008 Texas Dinophysis ovum bloom: Distribution and toxicity

Abstract

In early 2008, oyster beds along the Texas coast were closed due to the confirmed presence of okadaic acid (OA), the toxin responsible for diarrhetic shellfish poisoning (DSP). This marked the first shellfish bed closure in the United States due to both elevated concentrations of Dinophysis and DSP intoxicated shellfish. The population was dominated by Dinophysis ovum. In offshore samples, high concentrations (10,960 and 26,040 cells L −1) were observed in the southern coastal areas in mid to late February prior to the closure, and decreased through late February and early March. Dinophysis abundance increased at the northern areas 1–2 weeks later, although the sampling was insufficient to resolve if this was truly temporally distinct. Dinophysis was patchy at stations inshore of barrier islands, and many stations showed few or no Dinophysis. The high offshore abundance, and inshore bay distributions with maxima near barrier island passes, as well as the timing and magnitude of different peak concentrations, supports an offshore, southern origin for the Dinophysis bloom with advection into the bays. There was no correlation between abundance and environmental parameters, although cell density peaked offshore around 17–18 °C. Inshore occurrences showing a wider temperature range distribution for Dinophysis. Toxin content per Dinophysis cell (OA equiv. cell −1) showed no general pattern with time or conditions. Offshore and inshore maximum OA concentrations were high, but the bulk of the values fell within limits reported previously. Prorocentrum lima was not present, and the data suggests little or no contribution to the OA toxicity by Prorocentrum. With the addition of DSP, the northwestern Gulf of Mexico has among the highest diversity of harmful algal bloom (HAB) events in N. America, including ciguatera, Karenia brevis-neurotoxic shellfish poisoning (NSP), and brown tides. Domoic acid has been reported as well. NSP closures typically occur in late summer or fall. With the potential threat of DSP in the late winter or early spring now, the oyster industry in the NW Gulf of Mexico faces the potential for closures at virtually any time of the year, and possibly over most of the year.