<P> Plankton are a diverse group of organisms that live in the water column of large bodies of water and that cannot swim against a current . They provide a crucial source of food to many large aquatic organisms, such as fish and whales . </P> <P> These organisms include drifting or floating bacteria, archaea, algae, protozoa and animals that inhabit, for example, the pelagic zone of oceans, seas, or bodies of fresh water . Essentially, plankton are defined by their ecological niche rather than any phylogenetic or taxonomic classification . </P> <P> Though many planktonic species are microscopic in size, plankton includes organisms covering a wide range of sizes, including large organisms such as jellyfish . </P> <P> The role of phytoplankton is better understood due to their critical position as the most numerous primary producers on Earth . Phytoplankton are categorized into cyanobacteria (also called blue - green algae / bacteria), various types of algae (red, green, brown, and yellow - green), diatoms, dinoflagellates, euglenoids, coccolithophorids, cryptomonads, chrysophytes, chlorophytes, prasinophytes, and silicoflagellates . </P>

What kind of marine organisms are present in this figure