CARBON ASSIMILATION: DINOFLAGELLATES

Nearly 50% of the estimated 2377 dinoflagellate species are photosynthetic while a few are mixotrophic; these make an important contribution to the global biological carbon pump. We reviewed the involvement of pigments in the photosynthetic carbon assimilation and photoprotection in the athecate, thecate and symbiotic groups of dinoflagellates. We collated the much scattered and limited data on carbon assimilation in dinoflagellates. A variety of units for photosynthesis have been reported based on biomass expressed as cell numbers, chlorophyll a, cell carbon and cell volume which makes intercomparison of results difficult. The impacts of temperature, irradiance, nutrients in the carbon assimilation are discussed. Intra and inter specific variations in carbon assimilation are observed. Carbon assimilation was higher in heterotrophic dinoflagellates compared to autotrophic cultures. Mixotrophy provides a competitive advantage for long-term survival. Photosynthetic rates in dinoflagellate groups are low, even lower than the senescent cells of diatoms and microflagellates. Perhaps in the dinoflagellates, the channeling of energy for toxin production together with their need to support a disproportionately large DNA requires a heavy metabolic requirement and may explain their lower carbon assimilation rates.