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Dinoflagellates are single-celled flagellated organisms that make up a major part of oceanic plankton. They have both plant and animal characteristics and are known for causing harmful algal blooms and bioluminescence. They reproduce both asexually and sexually and have various adaptations to survive predators.
Dinoflagellates are a group of single-celled flagellated organisms that are considered a type of algae. Their name comes from the Greek dinos meaning “whirling” and scourge meaning whip. This is a reference to their characteristic whirling motion as they move through the water using two flagella: a longitudinal flagellum and a transverse flagellum. Dinoflagellates make up a major part of eukaryotic (complex unicellular) oceanic plankton, second in abundance only to diatoms.
Dinoflagellates are known as the source of red tides and one of the sources of oceanic bioluminescence. “Red tides,” also known as harmful algal blooms, occur when phytoplankton (photosynthesizing protists) release harmful chemicals into the water to kill fish and other organisms that threaten to eat them. These chemicals can leach moisture in the air and irritate the lungs and mucous membranes of people on the beach. The phenomenon is most common on the Gulf Coast of Florida. Sometimes red tides are caused by human activities, such as agricultural runoff, which provides an abundant source of nutrients for dinoflagellates. Harmful algal blooms are also associated with oxygen depletion, as organisms in red tide take up a lot of oxygen and then die, the oxygenated molecules in their bodies sinking to the sea floor.
Dinoflagellates have both plant and animal characteristics. They can photosynthesize, but are also mobile. Dinoflagellates have various adaptations to survive microscopic predators. Some species have a cellulose armor called theca, while others have body spikes called extrusomes, which can also release substances such as harmful chemicals outside the cell. Dinoflagellates reproduce both asexually, by dividing, and sexually, by combining with another member of its species and forming a zygote. The zygote releases substances that lock it inside a cyst, in a process called encystment. After a certain amount of time, the cyst ruptures and the cell divides, fresh with new genetic material. Cysts, called dinocysts, are the only representatives of dinoflagellates in the fossil record.
Dinoflagellates can be summarized as small (although some species are up to 2mm large), planktonic (90% are marine plankton), mobile, and often armored. Some dinoflagellates aren’t actually photosynthetic, but most are. Dinoflagellates are also characterized by their compact genomes, some of which have been fully sequenced.
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