Spin-up of the Baja California upwelling ecosystem’

The seasonal onset of coastal upwelling off Baja California was studied during March 1972. Time series of stations were taken for 2 weeks at 27”N off Punta San Hipolito; data on physical, chemical, and biological variables are used to estimate the source of up-welled water, the rate of nutrient input to the euphotic zone, and the rate of subsequent biological utilization. Red tide dinoflagellates were observed to be a precursor of the pre-sumably more typical diatom community of this upwelling ecosystem. This Gonyaulux polyedra dominated system suggests that these organisms lead to a longer food chain than that found later in the upwelling season. Pleuroncodes planipes, a facultative herbivore, was observed in large numbers but did not appear to be phytophagous during the transi-tion from an oceanic to an upwelling food chain. Early expeditions to upwelling regions of the eastern boundary currents (Gunther 1936; Defant 1936, 1937; Sverdrup 1938) provided static intraseasonal descriptions of these systems. More recent studies have stressed the interseasonal repeatability of their structure (Jones 1972; Maeda and Kishimot