What is a Dinoflagellate?

Mary McMahon
Mary McMahon

A dinoflagellate is a one-celled aquatic protist, found in both salt and fresh water. Dinoflagellates make up a large proportion of the plankton in the ocean, and are an important part of the life cycle in many aquatic environments. The creatures have been identified and studied since the 1700s, and have probably been around for millions of years, along with several other primitive organisms.

Dinoflagellate may inhabit coral reefs.
Dinoflagellate may inhabit coral reefs.

Like other protists, a dinoflagellate is difficult to classify because it possesses traits held by plants, animals, and fungi. There is also a great deal of diversity within the biological order Dinoflagellata, leading to varying lifestyles and morphologies for dinoflagellates. As a general rule, a dinoflagellate has a unique cellulose cell wall which forms a series of protective plates. It also has two unequally sized flagella, small arms which are used for locomotion. One flagellum, called the transverse flagellum, wraps around the body of the dinoflagellate, providing the bulk of propulsive energy, and the longitudinal flagellum trails behind, acting as a rudder.

Most of the plankton found in the ocean are dinoflagellates.
Most of the plankton found in the ocean are dinoflagellates.

The two flagella cause a dinoflagellate to appear to whirl through the water, inspiring the scientific name, which means “whirling whips.” Mobile dinoflagellates whirl through the water in search of energy, and often cluster in large amounts called blooms. In some cases, a bloom is unnoticeable and harmless, but in other instances, the dinoflagellates may contain or secrete toxins. This is the case with a red tide, a characteristic dinoflagellate bloom which turns the water slightly red. The toxins are absorbed by shellfish, which are unsafe to eat as a result of their contamination.

Approximately half of all dinoflagellates photosynthesize for their energy, while the other half form parasitic or symbiotic relationships with other animals. This is the case with dinoflagellates which inhabit coral reefs, for example. Some are bioluminescent, meaning that their bodies glow. A bloom of bioluminescent dinoflagellates can lead to the appearance of glowing or illuminated waves, as they emit light when they are disturbed. This bloom is generally harmless, and can be quite beautiful at night.

Depending on the species and the circumstances, a dinoflagellate can reproduce sexually or asexually. In many cases, a dinoflagellate simply splits to create offspring. In others, dinoflagellates will sometimes join forces, forming a multicellular organism which later splits into four in a process called meiosis. Scientific study has also revealed that dinoflagellates sometimes join forces in periods of stress or resource scarcity, bonding into a single stronger organism which splits once the crisis has passed.

Dinoflagellates are one-celled protists.
Dinoflagellates are one-celled protists.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


What are some examples of a dinoflagellate?


After swimming in toxic dinoflagellate-infested water, my grandfather became extremely ill. At first, he developed blisters and abcesses on his skin. Then, his eyes became red, he started vomiting, and he had trouble breathing.

By the time he got to the hospital, he could not even remember his name. He could not remember what 1+2 was, and he couldn’t read. During his stay, his kidneys and liver began to fail.

His was such a severe case that they could not save him. I don’t know how to tell a nontoxic bloom from a toxic one, so I just avoid swimming near all of them now.


Dinoflagellates also appear in sand, though they don’t live there for more than a day. This summer, I have seen the glowing sand myself, and it is pretty spectacular.

While kicking the sand at night, I saw it give off a greenish-blue spark. It reacted the same way when I stepped on it. In one area, I pulled my heel across a section about three inches long, and the streak left behind looked like a glow stick.

I could even see the dinoflagellates traveling back to sea in the receding waves. When the waves came in, they sucked up some of the sand full of the creatures, which twinkled as they got pulled back out to sea.


When the coast of Oregon sees a summer that is warmer than normal, large blooms of dinoflagellates may appear. My uncle is a marine biologist there, and he told me that warm summers create ideal weather conditions for “upwellings,” which are surges of cold water up from the deep. These surges bring nutrients for the dinoflagellates up to the surface. They can then multiply in large quantities.

Since the glow of dinoflagellates is dependent upon the sunlight they receive during the day, brighter days will produce more luminescence. If you go to the beach there at night after a sunny day, you will see the bloom reach its brightest glow about two hours after dark.


I saw the red tide while on vacation in New Zealand. It made for some amazing photographs.

I had been lounging on the shore with my beach chair partially in the water when I saw the bright red color coming in. Not wanting to get it on my skin, I decided to climb to the top of the seaside cliff to get a better view.

When I got to the top and looked out, I could see that the red swirls looked like marble cake. Rather than covering the entire surface like a blanket, it floated in stringy formations. If I had not known what it was, I might have guessed that it was lava traveling from an island volcano.

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