simple diffusion and laminar advective flow. Microalgae such as microphytes constitute the basic foodstuff for numerous aquaculture species, especially filtering bivalves. Photo- and chemosynthetic algae Photosynthetic and chemosynthetic microbes can also form symbiotic relationships with host organisms. They provide them with vitamins and polyunsaturated fatty acids, necessary for the growth of the bivalves which are unable to synthesize it themselves. In addition, because the cells grow in aqueous suspension, they have more efficient access to water, CO2, and other nutrients. Microalgae play a major role in nutrient cycling and fixing inorganic carbon into organic molecules and expressing oxygen in marine biosphere. While fish oil has become famous for its omega-3 fatty acid content, fish don't actually produce omega-3s, instead accumulating their omega-3 reserves by consuming microalgae. These omega-3 fatty acids can be obtained in the human diet directly from the microalgae that produce them. Microalgae can accumulate considerable amounts of proteins depending on species and cultivation conditions. Due to their ability to grow on non-arable land microalgae may provide an alternative protein source for human consumption or animal feed. Microalgae proteins are also investigated as thickening agents or emulsion and foam stabilizers in the food industry to replace animal based proteins. Some microalgae accumulate chromophores like chlorophyll, carotenoids, or phycobiliproteins that may be extracted and used as coloring agents. Cultivation of microalgae A range of microalgae species are produced in hatcheries and are used in a variety of ways for commercial purposes, including for human nutrition, as biofuel, in the aquaculture of other organisms, in the manufacture of pharmaceuticals and cosmetics, and as biofertiliser. However, the low cell density is a major bottleneck in commercial viability of many microalgae derived products, especially low cost commodities. Studies have investigated the main factors in the success of a microalgae hatchery system to be: Geometry and scale of cultivation systems (referred as photobioreactors); Light intensity; Concentration of carbon dioxide () in the gas phase Nutrient levels (mainly N, P, K) Mixing of culture See also AlgaeBase Raceway pond References External links NOAA, DMS and Climate Microalgae concentrates Microalgae research "From Micro-Algae to Blue Oil", ParisTech Review, Dec. 2011 Company Microphyt - Microalgae Production and Photobioreactor Design Biological oceanography Planktology Aquatic ecology