International Journal of Marine Science, 2025, Vol.15, No.5, 255-267 http://www.aquapublisher.com/index.php/ijms 255 Review Article Open Access Bioavailability of Phosphorus in Marine Ecosystems: Sources, Transport, and Ecological Impacts Zhen Liu, Shudan Yan Institute of Life Science, Jiyang College of Zhejiang A&F University, Zhuji, 311800, Zhejiang, China Corresponding author: shudan.yan@jicat.org International Journal of Marine Science, 2025, Vol.15, No.5, doi: 10.5376/ijms.2025.15.0023 Received: 05 Aug., 2025 Accepted: 25 Sep., 2025 Published: 10 Oct., 2025 Copyright © 2025 Liu and Yan, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Liu Z., and Yan S.D., 2025, Bioavailability of phosphorus in marine ecosystems: sources, transport, and ecological impacts, International Journal of Marine Science, 15(5): 255-267 (doi: 10.5376/ijms.2025.15.0023) Abstract Phosphorus is a fundamental and critical biogenetic factor in marine ecosystems, and its bioavailability directly affects the efficiency of marine primary productivity and biogeochemical cycles. In the marine environment, phosphorus mainly exists in two major forms: inorganic phosphates and organophosphorus compounds. Different sources and processes determine the input pathway and circulation mechanism of phosphorus. This study summarizes the main sources of ocean phosphorus and explores the characteristics of morphological transformation of phosphorus in the ocean. On this basis, the transportation and circulation mechanism of phosphorus are analyzed, covering the effects of physical processes such as ocean currents and upstream on phosphorus redistribution, as well as the impact of sedimentation-resuspension processes on phosphorus revenue and expenditure. Further, the status of phosphorus bioavailability in different sea areas and its ecological significance as a restricted nutrient salt is discussed, emphasizing the impact of changes in nitrogen-phosphorus ratio on the structure of phytoplankton community, the physiological adaptation strategies and gene regulation mechanisms of phytoplankton under phosphorus restriction. Finally, from the perspective of ecological and environmental, the impact of phosphorus circulation disorder on the coupling effect of marine food networks, the formation of marine hypoxic zones, and the feedback effect of phosphorus circulation in the context of climate change is discussed. Based on research progress in all aspects, this study emphasizes the core position of phosphorus in marine ecosystems and proposes prospects for future research on marine phosphorus cycles and sustainable marine management. Keywords Phosphorus restriction; Bioavailability; Nutrient cycle; Primary productivity; Red tide 1 Introduction Phosphorus (P) is an essential nutrient element that constitutes genetic material and energy molecules of biological cells, and plays an irreplaceable role in the structure and function of marine ecosystems. Compared with elements such as nitrogen (N), iron (Fe), phosphorus is considered to be the "ultimate" restrictive nutrient that limits ocean primary productivity on the geological time scale. Global phosphorus circulation profoundly affects marine biological pumps and global climate regulation through processes such as river output to the sea, internal ocean circulation, and marine sediment burial (Zhao et al., 2024). Enhanced recirculation of phosphorus in paleomarine environments has led to double the burial rate of organic carbon and significant global climate cooling, accompanied by the expansion of marine hypoxic zones, and has profound impacts on biological evolution (Guilbaud et al., 2020). In modern oceans, the concentration of surface phosphate is extremely low in oligotrophic areas far away from terrestrial sources in the ocean. The strong absorption of phosphorus by phytoplankton makes phosphorus often one of the main factors limiting primary productivity in these areas. Although the phosphorus concentration in nearshore waters often has a high concentration due to terrestrial input, there is also a phenomenon of relative phosphorus deficiency in the context of eutrophication, resulting in an imbalance of nutrient structure of "excess nitrogen and phosphorus shortage" (Maslukah et al., 2021). Phosphorus restriction not only directly restricts the growth, reproduction and community composition changes of phytoplankton, but also indirectly couples the carbon and nitrogen cycles of the ocean by affecting nitrogen fixation and organic carbon fixation. Therefore, in-depth study of the bioavailability of phosphorus in marine ecosystems is of great significance to understand the control mechanisms of global marine primary productivity and to address climate change and
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