International Journal of Marine Science, 2025, Vol.15, No.5, 255-267 http://www.aquapublisher.com/index.php/ijms 264 more organic carbon is settled, and the hypoxia is more serious. Therefore, it is often emphasized in eutrophication management that "phosphorus control" is because reducing phosphorus can effectively reduce the intensity of algae blooms and prevent large-scale hypoxia. 7.3 Feedback effect of phosphorus cycle in the background of climate change Global climate change may affect the ocean phosphorus cycle through multiple channels, which in turn will provide feedback on the climate system. Ocean warming and stratified enhancement may reduce upflow and vertical mixing, weaken deep phosphorus recharge, thereby reducing surface primary productivity and reducing marine biocarbon pump efficiency. This negative feedback mechanism means that warming causes less CO₂ to be absorbed by the ocean, which may accelerate the accumulation of atmospheric CO₂ (Niemeyer et al., 2016). Furthermore, ocean acidification may alter the chemical morphological availability of phosphorus. Some experiments have found that acidification reduces calcium carbonate deposition, causing the adsorption capacity of phosphorus on the particles to change, and at the same time affects the extracellular enzyme activity of phytoplankton. Terrestrial carbon-nitrogen coupled feedback is also involved in phosphorus, and warming may enhance the rate of phosphorus release on land weathering, which is part of the cooling feedback on the geological scale (Watson et al., 2017). 8 Conclusion As an essential element in life, phosphorus has a core position in marine ecosystems and runs through all aspects of primary production, food web transmission and biogeochemical cycle.The supply of phosphorus and bioavailability often determine the upper growth limit of phytoplankton and the level of primary marine productivity. In many areas, phosphorus is a restrictive nutrient or together with nitrogen and iron limits the production function of the ecosystem.When phosphorus is sufficient, the marine ecosystem can efficiently fix CO₂ and support a prosperous food web; when phosphorus is scarce, primary production and energy transfer are significantly suppressed, the ecosystem is in a low productivity state and community structure changes may occur.The phosphorus cycle regenerates phosphorus between the various ocean circles through complex physical transport and biological processes: ocean currents and upstreams redistribute phosphorus globally, bioabsorption and decomposition promote the conversion of phosphorus between organic and inorganic forms, and sedimentation burial and re-release regulates the revenue and expenditure of phosphorus banks on a long-term scale.Together, these processes maintain the dynamic balance of the ocean's phosphorus cycle, making the global ocean's nutritional pattern generally stable despite regional and period differences.Phosphorus is not only important for its own circulation, but it is closely coupled with the circulation of elements such as nitrogen, carbon, and iron, which jointly determines the balance of the source elements and climate regulation functions of the ocean. By reviewing the main sources of phosphorus, various forms and transformations in the ocean, circular transport mechanisms, bioavailability and restriction effects, and the ecological environment impact of phosphorus circulation disorders, we can see that ocean phosphorus circulation is a comprehensive system involving multiple scales and multiple processes. Land sources and seabed jointly provide marine phosphorus reservoirs. Different sources make different relative contributions in different regions. From coast to oceans, they gradually turn from rivers to atmospheric atmosphere. Geological sources cannot be ignored under local special environments.After entering the ocean, the phosphorus is constantly transformed between inorganic and various organic forms, and organisms play the main driver in it. Through enzymatic action, it converts difficult-to-use organic phosphorus into available phosphates to achieve nutrient regeneration.The ocean current and biological pump process migrate the phosphorus in a vertical and horizontal direction, making the surface-deep, near-shore-ocean related to each other. Research on marine phosphorus cycle has many implications for future sustainable development of oceans.In terms of eutrophication and red tide management, controlling phosphorus emissions and imports is one of the key measures.Unlike nitrogen, there is currently no phosphorus storage in the atmosphere and it is difficult to survive
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