Spatial and temporal trends of the toxic diatom Pseudo-nitzschia in the Southeastern Atlantic United States

Abstract Data collected by NOAA Phytoplankton Monitoring Network volunteers, from the beginning of the program (2001) through 2010, was used to assess the spatial and temporal trends of Pseudo-nitzschia spp . from North Carolina through northern Florida along the southeastern US coastline. Pseudo-nitzschia spp . was present from North Carolina to Florida, and was most common in North and South Carolina. Across the majority of the Atlantic southeast US, the highest rates of occurrence were observed in late summer, early fall, with most areas experiencing the lowest rate of occurrence in the spring. The Outer Banks of North Carolina, however, experienced a peak of occurrence in late winter to early spring in addition to a late summer, early fall peak. Pseudo-nitzschia was found in temperatures ranging from less than 5 °C to 35 °C and salinities from 5 to 37. Six unique bloom events were documented during this period of nine years, three of which contained detectable levels of domoic acid. The majority of these bloom events and all of the toxic events occurred in the Outer Banks of North Carolina. Given the extent and intensity of coverage afforded by the NOAA PMN, this program provides the optimal approach to not only assess past trends but to monitor environmental changes and emerging trends in the dynamics of this toxigenic species. Understanding the dynamics of this species allows resource managers to better predict the threats associated with domoic acid.