During a sampling on 16-17 January 2013 in the southwest part of Bahía de La Paz, a moderate bloom of the dinoflagellate Ceratoperidinium falcatum was detected. Its abundance varied from 11,200 to 145,400 cells L–1 during this period in seawater temperature at 23°C and salinity of 35.42. The specimens were solitary cells. Few two-celled chains were observed. Young cells were relatively small, 30-70 mm long; 17-36 mm wide, from ovately elongate to fusiform. Mature individuals were 40-190 mm long and 20-36 mm wide. Including C. falcatum, 21 species belonging to 5 orders of unarmored dinoflagellates were identified during this bloom. Four species are new records for the Gulf of California and three are new records for the Pacific coast of Mexico.
