Abstract

GIS Analysis of Harmful Algal Blooms in Southern California
Track: Ocean, Coastal, and Marine Resources
Author(s): Rebecca Schaffner, Astrid Schnetzer, David Caron

Toxic blooms of the domoic-acid producing diatom genus Pseudo-Nitzschia have occurred repeatedly in the waters of Southern California in recent years, resulting in extensive mortality of marine mammals and seabirds. We report on studies carried out between 2003-2007 in which we sampled sea-surface stations during bloom and non-bloom periods. ArcMap and the Spatial Analyst extension were used to interpolate and analyze concentrations of toxins, phytoplankton, and dissolved nutrients in surface waters. Water temperature, river discharge, and upwelling were also analyzed. Preliminary results indicate that both coastal upwelling and river discharge were followed by periods of increased algal biomass. However, river discharge seemed to promote species other than Pseudo-nitzschia while high Pseudo-nitzschia abundances and domoic acid toxin production were associated with periods of upwelling and decreased river runoff. We also found that Pseudo-nitzschia and domoic acid were inversely correlated with dissolved nutrients such as phosphate and silica.

Rebecca Schaffner
SCCWRP
3535 S. Harbor Blvd
Costa Mesa , California 92626
United States
Phone: 714-755-3243
E-mail: beckys@sccwrp.org

Astrid Schnetzer
University of Southern California
3616 Trousdale Parkway
Los Angeles , California 90089
United States
Phone: 213-821-1800
E-mail: astrids@usc.edu

David Caron
University of Southern California
3616 Trousdale Pkwy
Los Angeles , California 90089
United States
Phone: 213-821-1800
E-mail: rschaffn@usc.edu