User:MitchKrings/Phosphorus cycle

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The phosphorus cycle is the biogeochemical cycle that involves the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based materials do not enter the gaseous phase readily. The production of phosphine gas occurs in isolated and specific conditions. Therefore, the phosphorus cycle is primarily examined studying the movement of orthophosphate (PO4)3-, the form of phosphorus that is most commonly seen in the environment, through terrestrial and aquatic ecosystems.

Living organisms require phosphorus, a vital component of DNA, RNA, ATP, etc., for their proper functioning. Plants assimilate phosphorus as phosphate and incorporate it into organic compounds. In animals, phosphorus is a key component of bones, teeth, etc. On the land, phosphorus gradually becomes less available to plants over thousands of years, since it is slowly lost in runoff. Low concentration of phosphorus in soils reduces plant growth and slows soil microbial growth, as shown in studies of soil microbial biomass. Soil microorganisms act as both sinks and sources of available phosphorus in the biogeochemical cycle. Furthermore, phosphorus tends to be a limiting nutrient in aquatic ecosystems. However, as phosphorus enters aquatic ecosystems, it has the possibility to lead to over-production in the form of eutrophication, which can happen in both freshwater and saltwater environments. Short-term transformation of phosphorus is chemical, biological, or microbiological. In the long-term global cycle, however, the major transfer is driven by tectonic movement over geologic time.

Humans have caused major changes to the global phosphorus cycle primarily through the mining and subsequent shipping of phosphorus minerals for use in fertilizer and industrial products. Some phosphorus is also lost as effluent through the shipping process as well.

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Oceans

As previously shown, lakes are a prime target for eutrophication with many examples being studied. Oceanic ecosystems gather phosphorus through many sources, but it is mainly derived from weathering of rocks containing phosphorus which are then transported to the oceans in a dissolved form by river runoff. Due to a dramatic rise in mining for phosphorus, it is estimated that humans have increased the net storage of phosphorus in soil and ocean systems by 75%. This increase in phosphorus has led to more eutrophication in ocean waters as phytoplankton blooms have caused a drastic shift in anoxic conditions seen in both the Gulf of Mexico and the Baltic Sea. Some research suggests that when anoxic conditions arise from eutrophication due to excess phosphorus, this creates a positive feedback loop that releases more phosphorus from oceanic reserves, exacerbating the issue. This could possibly create a self-sustaining cycle of oceanic anoxia where the constant recovery of phosphorus keeps stabilizing the eutrophic growth. Attempts to mitigate this problem using biological approaches are being investigated. One such approach involves using phosphorus accumulating organisms such as, Candidatus accumulibacter phosphatis, which are capable of effectively storing phosphorus in the form of phosphate in marine ecosystems. Essentially, this would alter how the phosphorus cycle exists currently in marine ecosystems. Currently, there has been a major influx of phosphorus due to increased agricultural use and other industrial applications, thus these stored organisms could theoretically store the phosphorus and it could be recycled into terrestrial ecosystems which would have lost this excess phosphorus due to runoff.

More Sources of human phosphorus increases

Humans have greatly altered the phosphorus cycle through a myriad of ways. The most prominent comes from a major increase in mining of phosphate rock. For millennia, phosphorus was primarily brought into an environment through the weathering of phosphate containing rocks, which would replenish what was lost to the environment, albeit on a very slow and gradual time-scale. Since the 1840s, when the technology to mine and extract phosphorus became more prevalent, approximately 110 Tg of phosphorus has been added to the environment. This trend doesn't appear to be slowing down as from 1900-2022, the amount of phosphorus mined globally has increased 72-fold, with an expected annual increase of 4%. Most of this mining is done in order to produce fertilizers which can be used on a global scale. However, at the rate humans are mining, the geological system can not restore what is lost quickly enough. Thus, researchers are examining ways to better recycle phosphorus in the environment, with one promising application including the use of microorganisms. Regardless, humans have had a powerful impact on the phosphorus cycle with wide-reaching implications about food security, eutrophication, and the overall availability of the nutrient.