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Michail Gladyshev, Institute of Biophysics of Siberian Branch of Russian Academy of Sciences, Russian Federation;
Humans and most other animals need food sources of physiologically important highly unsaturated fatty acids (HUFA), such as eicosapentaenoic acid, (EPA) and docosahexaenoic acid (DHA), because their own synthesis of these HUFA can cover only around 5% of their physiological requirements. Among all organisms only some microalgae, diatoms, cryptophytes and dinophytes can synthesize de novo high amounts of EPA and DHA. HUFA, synthesized by microalgae, are transferred through trophic chains to organisms of higher levels, invertebrates and fish. Thus, aquatic ecosystems play the unique role in the Biosphere as the principal source of EPA and DHA for most animals, including inhabitants of terrestrial ecosystems and humans. HUFA are transferred from aquatic to terrestrial ecosystems through riparian predators, shore drift, emergence of amphibiotic insects and water birds. These essential nutrients are transferred through trophic chains with about twice higher efficiency than bulk carbon. Thereby, HUFA are accumulated, rather than diluted in biomass of organisms of higher trophic levels, e.g., in fish. Humans withdraw from aquatic ecosystems through fish catch ~180 106 kg y-1 of EPA+DHA. However, global average personal daily consumption of EPA+DHA is only about 0.1 g, while healthy personal intake is 0.5 – 1.0 g day-1. Thus, humankind face with a deficiency of the physiologically important HUFA in diet. Potential ways to increase HUFA consumption are discussed. Aquaculture is based on forage, obtained from wild catch and thereby cannot substitute fishery. Microbial biotechnology – single cell oil production is cost-prohibitive. Thereby, natural fish production of aquatic ecosystems will remain the main sources of the essential PUFA for humans. Aquatic ecosystems differ significantly in HUFA production of microalgae and thereby various fish species, getting PUFA from microalgae through trophic chains, differ in EPA and DHA contents in their biomass in two orders of magnitude. Ways to increase HUFA production in natural aquatic ecosystems are discussed. Data on quantity of various fish products to be consumed for obtaining the recommended appropriate intake of EPA+DHA for humans are given.