Marine life asexually by binary fission, fragmentation, or budding; unlike bacteria and eukaryotes, no known species forms spores. Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle. Of eukaryotic groups, the protists are most commonly unicellular and microscopic. This is a highly diverse group of organisms that are not easy to classify. Several algae species are multicellular protists, and there are marine slime molds have
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