Variability of the phytoplankton community in San Quint?Bay based on pigment analysis

The purpose of this work was to characterize the phytoplankton community of San Quintín Bay using pigment concentrations from HPLC and the CHEMTAX program, so that small cells (< 5 µm) would not be excluded. On 23–24 April 2001, a 24-h time series was generated, sampling surface water every hour. Samples were also taken from six localities throughout the bay. There was a significant contribution of seven phytoplankton groups. Those that contributed the most to total chlorophyll a were cryptophytes, cyanobacteria, bacilliarophytes and chlorophytes. In general, pigment concentrations were higher in the mouth region and decreased towards the internal extremes. This is the first report of the presence of the pigment divinyl chlorophyll a in San Quintín Bay, which firmly suggests the presence of Prochlorococcus sp. This group contributed up to 40% of the total chlorophyll a. Other cyanobacteria contributed up to 13% of the total chlorophyll a. These percentages are indicative of a very high abundance of these groups.