Phytoplanktonic temporal variability in a coastal area of northwestern Baja California

Abstract

A phytoplankton study was barried out in Bahía de Todos Santos from March 1986 to March 1987. Samples were taken monthly at three stations and at depths of 1, 10 and 20 m. The temporal variability of the phytoplankton taxonomic groups was very similar most of the time, except in June and November when an increase in the diatom group was detected. These cell blooms may be due to mixing processes or upwelling events that occur outside the study area. The advection process into the bay is shown by the low oxygen saturation values for June at 20 m depth. The size fractions of diatoms showed two successional phases of bloom events: in June, an abundance of cells was observed with late-bloom characteristics since the predominant cell size of the diatom group was > 20um, whereas in November there was a dominance of cells < 20 µm, characteristic of a prebloom event.