Seasonal occurrence of planktonic dinoflagellates and cyst production in relationship to environmental variables in subtropical Bahı´a Concepción, Gulf of California

We studied seasonal prevalence of dinoflagellates and of cyst production in relation to hydrological factors in Bahía Concepción, Mexico. In situ production of dinoflagellate cysts was recorded for the first time in Mexico. The resting stage of toxic Gymnodinium catenatum, potentially toxic Alexandrium pseudogonyaulax, and other red tideforming dinoflagellates were collected in traps. Cyst associations were linked with the composition of vegetative stages in the water column, and production yields (128 to 1.465×106 cysts m-2 d-1) were comparable with other reports in areas around the world. Seasonal abundance of major meroplankton dinoflagellates and relationships with yields of newly-formed cysts coincides with hydrographic transitional periods in the water column in spring and early fall. From factor analysis, the physico-chemical variables that correlate with the presence of the major meroplanktonic species are, in descending order of importance: temperature, phosphates, dissolved oxygen, silicate, nitrite, and nitrate. In Bahía Concepción, Gonyaulacales and Scrippsiella trochoidea cysts are present during declines in algal blooms as a mechanism to counteract adverse conditions, and to secure an inoculum for blooming when favorable conditions return. In contrast, G. catenatum cysts maintain the motile stage over prolonged periods with recurrent germination.