Dinoflagellates are single-celled organisms that live in oceans, estuaries, lakes, and ponds. Some of them are bioluminescent -- they cause a sparkling of the sea at night as the waves break. Some of them cause "red tides," which can kill fish or poison humans who eat the fish or shellfish that have eaten the dinoflagellates. The Red Sea may have gotten its name from dinoflagellate blooms.
Dinoflagellates are most often considered to be plants because many make their own food using air, water, and sunlight. Some dinoflagellates eat other plants or eat small or large animals. Some live within animals such as corals.
Many dinoflagellates have a complex life cycle that includes a resting stage. During this stage, the dinoflagellate may live in a very durable capsule called a dinocyst. The dinocyst is studied by paleontologists. Unlike many other fossils, the dinocyst is not a dead dinoflagellate. It is more like a cocoon. There is an opening in the dinocyst through which the dinoflagellate, like a butterfly, exited and went on its merry way.
Dinocysts are found in the muds, sands, and other sediments at the bottoms of modern ocean, estuaries, lakes, and ponds. They are found as fossils in mudstones, sandstones, and limestones formed long ago.
Age and Environment - Dinocysts are used to help deduce the age and environment of rocks or sediments. They are most useful in marine rocks from the Late Triassic to the present. The age of sedimentary rocks provided by dinocysts is important to geologic mapping, to understanding the structural geology of an area, and to understanding the movement of ground water of an area. Dinocysts are used in studies of past environments to model climate change, to analyze past ocean currents, and to detect past or present pollution.
Lucy E. Edwards, Reston, VA, biostratigraphy of the Atlantic and Gulf Coastal Plains.