Marine life 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. 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. Though many planktonic species are microscopic in size, "plankton" includes organisms covering a wide range of sizes, including large organisms such as jellyfish. The
Culture of microalgae in hatcheries Culture of microalgae in hatcheries Microalgae or microscopic algae grow in either marine or freshwater systems. They are primary producers in the oceans that convert water and carbon dioxide to biomass and oxygen in the presence of sunlight. The oldest documented use of microalgae was 2000 years ago, when the Chinese used the cyanobacteria "Nostoc" as a food source during a famine. Another type of microalgae, the cyanobacteria "Arthrospira" (Spirulina), was a common food source among populations in Chad and Aztecs in Mexico as far back as the 16th century. Today cultured microalgae is used as direct feed for humans