are diatoms seaweed and phytoplankton
Dinoflagellates. Dinoflagellates are the other primary form of large phytoplankton with about 2,000 species. Unlike diatoms, dinoflagellates are mobile through the use of a flagella. Also unlike diatoms, they do not have an external skeleton made of silica, however they are protected by cellulose.arine algae (seaweeds and phytoplankton) are a loose group of some of the simplest organisms that contain chlorophyll (like plants) but include members of both the Empires Prokaryota (Kingdom Bacteria-e.g., cyanobacteria) and Eukaryota (Kingdoms Chromista, Plantae and Protozoa...).