Overview of the ecology of HABs in upwelling systems on the U.S. West Coast

Vera L. Trainer

Marine Biotoxin Program, NOAA Fisheries, 2725 Montlake Blvd. E., Seattle, Washington, 98112, USA
Vera.L.Trainer@noaa.gov

The food web transfer of the toxin, domoic acid, to shellfish, crustaceans, seabirds, finfish and marine mammals has been recently documented on the U.S. West coast. Data collected during West coast cruises in the years 1997-2001 indicate that often the highest toxin levels and greatest numbers of toxic cells are positioned in water masses associated with offshore eddies, such as the Juan de Fuca eddy or in upwelling zones near coastal promontories, such as Heceta Bank, Oregon, and Point Conception, California. Beach samples collected in 1998 indicated that a Pseudo-nitzschia pseudodelicatissima bloom was responsible for razor clam toxicity on the Washington coast, whereas toxin produced by P. australis resulted in sea lion mortalities in central California. The detection of toxin in urine, feces, and stomach contents of several sea lions represents the first proven occurrence of domoic acid transfer through the food chain to a marine mammal. The pennate diatoms, P. multiseries and P. australis, were the dominant, toxin-producing phytoplankton constituting algal blooms in California near Monterey Bay, Half Moon Bay, and Oceano Dunes, areas where sea lions with neurological symptoms stranded. Toxic Pseudo-nitzschia were also found near Morro Bay, Point Conception, Point Arguello, and Santa Barbara, demonstrating that these species were widespread along the central California coast in June 1998. Measurements of particulate domoic acid during three cruises during the summers of 1997 and 1998 showed the highest toxin levels in P. multiseries near Point Año Nuevo at 6 pg cell^-1, in P. australis from Morro Bay at 78 pg cell^-1, and in P. pseudodelicatissima from the Juan de Fuca eddy region at 4 pg cell^-1. Maximum cellular domoic acid levels were often observed between 0 and 10 m depth, although toxin was also measured to depths of 40 m.