MEPS 327:119-133 (2006)  -  doi:10.3354/meps327119

ABSTRACT: During May 2003, a toxigenic bloom of the diatom Pseudo-nitzschia australis occurred in the Santa Barbara Channel (SBC), California, that was linked to a marine mammal mortality event in the region. Satellite imagery revealed the presence of the bloom prior to a period of strong, spring upwelling along the continental shelf of the SBC. Following upwelling the bloom increased in areal extent to cover most of the SBC. P. australis abundance ranged from 0.4 × 10⁵ to 2 × 10⁶ cells l^–1 with particulate domoic acid (DA) concentrations between 32 and 1684 ng l^–1. Significant negative correlations between silicic acid, Si(OH)₄:NO₃^– and Si(OH)₄:PO₄^3– ratios and particulate DA suggest that the bloom may have been experiencing Si limitation. High cell abundance and the highest levels of cellular DA (0.14 to 2.1 pg cell^–1) were associated with a cyclonic eddy in the western end of the SBC. Cyclonic eddies within the SBC are known to be convergent, and may thus have concentrated P. australis cells within this feature. Propagation of the eddy transported the bloom to the west, indicating that coherent circulation features may help predict the fate of harmful algal blooms in coastal systems.

KEY WORDS: Domoic acid · Pseudo-nitzschia spp. · Pseudo-nitzschia australis · Cyclonic eddy · Upwelling · Bio-physical coupling · Southern California Bight