Dinoflagellates

The Dinoflagellates are a type of Phytoplankton. Phytoplankton are tiny floating plants that produce about half the worlds oxygen. Phytoplankton are also the bottom level of the aquatic food web. Dinoflagellates are photosynthetic which means that they are a yellow-green and sometimes even red. These photosynthetic Phytoplankton have 2 flagella which enable them to move more instead of just floating. Of the 2000 species of Dinoflagellates 60 species produce toxins that can be harmful to animals and humans. These phytoplankton are the cause of Red Tide. The toxins that they produce causes pfiesteria, which means death to anything that comes in contact with it. Dinoflagellates are not all bad, they are also mutualistic in corals.

http://cimt.ucsc.edu/habid/Diatom_Dino.html