Inorganic and Organic Reservoirs for Phosphorus
The phosphorus cycle originates in sediments. Sediments are the primary inorganic reservoir for phosphorus. Unlike that of the nitrogen and carbon cycles whose main reservoir is the atmosphere. Natural inorganic phosphorus occurs as phosphate in the mineral apatite. This mineral is often found in igneous, metamorphic, and sedimentary rocks. Phosphorus usually isn’t available for uptake in soils. Most of the phosphorus in soil is rather absorbed into soil particles or incorporated into organic matter. Inorganic and organic phosphorus undergo continuous transformations.
Dissolved phosphorus is assimilated by phytoplankton in marine ecosystems and then altered to an organic form. The phytoplankton are then ingested by another organism, such as zooplankton for example. From there half of the phosphorus ingested is excreted as an inorganic substance and the cycle continues.
Phosphorus is also taken up by the plants from the soil as inorganic and then manufactured into an organic molecule such as ATP. When herbivores consume these plants the organic Phosphorus incorporates into their tissues. This continues up the food chain. It can be released back to the soil through animal excretion, also when animals die decomposers break down and mineralize the organic phosphorus into and inorganic substance that returns to the soil to restart the cycle.
Some phosphorus is removed completely from the cycle. This occurs when phosphorus-containing particles settles to the bottom of phosphorus sinks, lakes and reservoir sediments. They are then rapidly covered by sediment. When this sediment accumulates it will sometimes leave the phosphorus too deep within the substrate to be released back into the water column.
Dissolved phosphorus is assimilated by phytoplankton in marine ecosystems and then altered to an organic form. The phytoplankton are then ingested by another organism, such as zooplankton for example. From there half of the phosphorus ingested is excreted as an inorganic substance and the cycle continues.
Phosphorus is also taken up by the plants from the soil as inorganic and then manufactured into an organic molecule such as ATP. When herbivores consume these plants the organic Phosphorus incorporates into their tissues. This continues up the food chain. It can be released back to the soil through animal excretion, also when animals die decomposers break down and mineralize the organic phosphorus into and inorganic substance that returns to the soil to restart the cycle.
Some phosphorus is removed completely from the cycle. This occurs when phosphorus-containing particles settles to the bottom of phosphorus sinks, lakes and reservoir sediments. They are then rapidly covered by sediment. When this sediment accumulates it will sometimes leave the phosphorus too deep within the substrate to be released back into the water column.