Spin‐up of the Baja California upwelling ecosystem1

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 upwelled 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 presumably more typical diatom community of this upwelling ecosystem. This Gonyaulax 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 transition from an oceanic to an upwelling food chain.