A Recurrent Red Tide in a British Columbia Coastal Lagoon

The development of a recurrent fall red tide in Esquimalt Lagoon, British Columbia, has been monitored over an 8-yr period, including an intensive 1-yr field study. We suggest that growth of the organism, Gymnodinium sanguineum Hirasaka, which causes the tides, is regulated by the availability of nitrate supplied in runoff. Its decline is attributed to the seasonal decrease in the availability of light. The source of the seed population for these recurring blooms is unclear, although we propose that transport from California by the California Undercurrent is involved.