Diatoms are single-celled algae that add silica to their cell walls for strength. Their shells are very complex and are occasionally used in polishes and toothpaste, as a binder. There are about 70 species of dinoflagellates around the continent of Antarctica. Dinoflagellates are a single-celled algae with a nucleus. They are round and are mostly the same as the diatoms except that they produce nasty toxins.
Red tides are very dangerous because they can kill an animal that ingests the substance.
Luckily, these do not happen around Antarctica because the numbers of dinoflagellates inhabiting the waters are not large. Silicoflagellates are the least prevalent species of phytoplankton. They are most prevalent where diatoms live, but they are a different kind of phytoplankton. Their skeleton is made up of long tubular rod-shaped elements, and they can propel themselves through the water with a eucaryotic flagellum, which is a whiplike extension of certain cells or unicellular organisms that functions as an organ of locomotion. Waters high in phytoplankton provide essential food for krill and other small marine animals.