Phosphorus comes into the ecosystem due to the weathering of rocks (see Ecosystem Services). The productivity of the lakes is proportional to the phosphate availability. For instance, soda lakes are often eutrophic in spite of extreme environment and limitation by other elements. Phosphorus is mobilized from its minerals by many acid-producing microorganisms, which make dissolution zones on the plates with an enamel of phosphate containing minerals. Phosphorus of the sea has terrestrial origin. Assimilated phosphate is included into the nucleic acids and phospholipids of the biomass. Regenerative cycle of phosphorus includes liberation of phosphate by the action of phosphatases. Phosphorus escapes from the cycle by binding into insoluble compounds of phosphorites on reaction with Ca and F. It should be noted that deposits of micritic phosphorites were formed by cyano-bacterial mat; phosphatisized microfossils of cyanobacteria are clearly visible in the scanning electron microscope. Cyanobacteria store phosphate as intracellular polyphosphate, which is the transitional source for rapid phosphatization. The iron pump demonstrates liberation of phosphate in anoxic environment: ferric iron binds phosphate in an insoluble compound but reduction to ferrous state liberates phosphates. On a large scale, phosphorus is the limiting element for primary production, which depends on its availability.
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