Orthophosphate phosphorus cycle

Incubation of lake water with 32P or 33P as tracers and subsequent gel chromatography reveals that a major pathway exists between dissolved orthophosphate and the particulate phase (3, 5-7). Low-molecular-weight phosphorus forms in the presence of bacteria and algae. SUP is present in the low-molecular-weight fraction and is classified as individual DOP compounds unassociated with particulate or colloidal material. The HMW fraction found in gel chromatography studies is characterized as a colloid that contains phosphorus compounds or incorporates orthophosphate. The colloidal material then releases orthophosphate, replenishing the dissolved phosphorus cycle. In some eutrophic lakes the HMW SRP fraction can make... 

Very little detail is known about the nitrogen and phosphorus cycles. Dissolved orthophosphate is taken up in plant growth and returned eventually after serving in cell fluids and tissues. It appears to be released primarily in the form of organophosphorus compounds, and at certain seasons of the year more than half the phosphorus in the water is described as "dissolved organic phosphorus. Yet as of a year or so ago... 

Major differences in size (filterable, particulate) and chemical reactivity (condensed, organic) of phosphorus forms in samples can be used as the basis for speciation, as shown in Table 1. Of these fractions, total phosphorus (TP) and FRP are perhaps the most commonly measured, although it is arguable that the understanding of the aquatic phosphorus cycle is somewhat lopsided because of that bias. For example, wastewater discharge licenses often specify a maximum permissible concentration of TP, and provide an indication of the maximum potentially bioavailable phosphorus discharged. However, FRP, comprising mostly orthophosphate, is a measure of the amount of most readily bioavailable phosphorus. 

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