Population structure and in situ division rates of Ceratium in oligotrophic waters of the North Pacific central gyre1

Abstract

Species composition and division rates were examined for a population of the dinoflagellate genus Ceratium from oligotrophic waters of the North Pacific central gyre. Division rates of Ceratium were high relative to those in other oceanic regions despite the low nutrient levels. Doubling times were calculated to be 5.2–7.5 days for the genus and ranged from 4.0 to 9.2 days among the 10 most abundant species. Fifty‐one species of Ceratium were identified, and their rank order of abundance was remarkably constant over the largest temporal and spatial scales examined (9 months and 755 km). Ceratium's relatively high division rate coupled with its consistently low abundance supports the conclusion from other data that steady state conditions are approximated in this environment.