Abstract
During a 1-year intensive monitoring program of Esquimalt Lagoon, B.C., a red tide occurred in September and October, 1978, involving the non-toxic dinoflagellate Gymnodinium sanguineum. Detailed information is therefore available for the period leading up to, during and following the red tide. A number of factors are considered with respect to their roles in initiating, maintainoing and terminating the bloom, including temperature, salinity, hydrography, light, macro- and micronutrients, competition and predation. It is ocncluded that all phases of the bloom were regulated principally by the availability of inorganic nitrogen, although not all aspects of its development can be explained in these terms.