# Phosphorus biogeochemistry

The phosphorus cycles takes place between the biosphere, hydrosphere, and geosphere. Since phosphorus does not have a gaseous form, little to no phosphorus is transferred through the atmosphere. The availability of phosphorus is dependent on the environment and is often a limiting nutrient commonly called the "disappearing nutrient." Even though this "disappearing nutrient" is limited, it is an essential material for organisms. Phosphorus is used for energy transfers, genetic material, membrane compositions, etc. and the amount available can affect distribution of species, primary productivity, biomass, etc. The forms that phosphorus generally exist as are dissolved and particulate forms, either as inorganic or organic, and generally have low solubility. Organisms have found ways to use these different forms of phosphorus, or found alternative nutrients, to deal with the availability in different environments.
One huge impact on phosphorus in the environment is human activity which mostly increased its availability through the use of P fertilizers. Increased phosphorus can induce an increase in toxic algal blooms (eutrophication), loss of biodiversity, an increase in fish death, etc. Phosphorus used in agriculture as fertilizers typically is derived from sedimentary rocks that are mined.
The overall cycle is as follows: rocks weather and erode and release phosphates that can be depositied in the soil and/or can travel to the oceans. In both land and ocean, primary producers uptake phosphate to produce organic compounds and the phosphate taken up is excreted back into the soil/water or gets put back through decomposition of an organism.

## Terrestrial Phosphorus Cycle

There are three dominant pools of phosphorus in terrestrial ecosystems: continental bedrock, soil, and biomass. An important sink within those pools is in the Earth's crust where a majority of phosphorus is in apatite. Organic phosphorus that can be found in soils and sediments are in biomass and are predominantly as orthophosphate monoesters. These orthophosphate monoesters play a key role in photosynthesis.

### Phosphorus regulation in soil

Phosphor is controlled and regulated by physical, chemical, or biological processes. Environmental factors that affect availability of phosphor include weathering and erosion, different rock types, soil pH, precipitation, deforestation and habitat loss, temperature, decomposition rates, etc.
An important regulation of phosphor includes carbonates in the soil. Calcium carbonate effects phosphor at three different levels: elemental, surface, and environmental. Phosphor is adsorbed on carbonate minerals either as a fast reaction or a slow reaction, as obligate adsorption or partly multilayer adsorption, by binding to free metals found on carbonate sites. These metals typically include either Mg$^{2+}$ or Ca$^{2+}$.

## Marine Phosphorous Cycle

Oceans primarily receive phosphor through continental weathering, generally in dissolved and particulate phases. Another method is atmospheric deposition to remote locations in the oceans. This is important, but since phosphor does not have a gaseous form this is a very small percentage of phosphorus transfer, but is important for the open ocean where nutrients are limited. Within the ocean, some important forms of phosphor include: dissolved inorganic phosphor (DIP), phosphate, dissolved organic phosphor (DOP), etc. DOP is highly utilized and a valuable commodity for marine microbes, as well as can be re-mineralized twice as fact compared to other dissolved nutrients (like carbon or nitrogen). The largest transport of phosphor is through biological uptakes; organic matter burials. Other mechanisms of phosphor transport include phosphor sorption and precipitation, phosphorite burial, and even hydrothermal processes. Upwellings within the oceans can also serve as a negative feedback mechanism for oceanic phosphor mass balance.<

### P availability affects on microbes

Limited phosphor availability in the ocean has induced microorganisms to be flexible. Some adaptations that have been used include phosphorus conservations, phosphorus limitation responses, and phosphorus niche partitioning. Plankton, for example, can use phosphor free alternatives instead of phosphor lipids when they are phosphor starved. Some prokaryotes can use a periplasmic buffer to secure phosphor and there are also picocyanobacteria that contain a large number of high affinity phosphate binding proteins.

### P availability affects on Biogeochemical cycles

Limited availability of phosphor also affects other nutrient cycles. One way is by influencing carbon fixation during photosynthesis, leading to an influence on export production and global climate; carbon flow has a dependence on the amount of DOP available. The nitrogen cycle is also impacted by DOP availability in that using DOP can provide an advantage to N$_2$ fixing microbes.

## Human Impacts on the Phosphorus Biogeochemical Cycle

Agriculture has a huge impact on the phosphorus cycle. There are fertilizers made to help combat phosphor limitations from mining phosphorus rocks, leading to excess phosphor being washed into rivers and groundwater from both the fertilizers in crop production and the erosion of the rocks. Since the pre-anthropogenic era, the flux of phosphor has at least doubled. A few issues come with this phosphor output. Anthropogenic activities can drive Eutrophication (can increase with an increase in phosphor levels, though not as affected as with an increase in nitrogen levels), limited regions to phosphor limited regions, and even cause a loss of biodiversity.