Occurrence of Cochlodinium fulvescens (Gymnodiniales: Dinophyceae) in the southwestern Gulf of California

Abstract

The naked dinoflagellate Cochlodinium fulvescens was rarely observed in Bahía de La Paz since 2008. Sporadic observations were made in 2010 and 2012. The species re-appeared from October 2012 to April 2013. Abundance of C. fulvescens ranged from 600 to 45,800 cells L-1 during this period in seawater temperature at 22-27°C and salinity of 35.25-35.75. This species appeared as single cells or two-celled chains and co-occurred with Cochlodinium polykrikoides at the end of the bloom. C. fulvescens usually occurs in autumn to spring and C. polykrikoides usually occurs in spring to autumn. The main distinguishing morphological characters between these two species are the relative position of the cingulum and sulcus and the morphology of chloroplasts. This provided reliable identification of live cells. Other Cochlodinium species, such as C. faurei, C. pulchellum, and C. rosaceum were also observed in the bay.