International Journal of Marine Science, 2025, Vol.15, No.5, 255-267 http://www.aquapublisher.com/index.php/ijms 260 strong storms, bottom trawls, etc. cause surface sediments to resuspend, the phosphorus adsorbed on the particles will reenter the water column. For example, the Bohai Sea and the East China Sea shallow Sea often observe an increase in the concentration of phosphorus in water after winter storms, that is, it is derived from the contribution of resuspended and remineralized sediments. 4.4 Case analysis: phosphorus cycle dynamics in peruvian upflow system The Eastern Pacific Peruvian upflow system is a classical area for studying the ocean's phosphorus cycle. The sea area is known for its strong coastal uplift and extensive oxygen minimum belt, with extremely high primary productivity, and at the same time, the underlying water body is hypoxia or even anaerobic. Phosphorus has some unique characteristics in this cycle. During the upwelling season, a large amount of deep phosphorus-rich water surges to the surface, causing the phosphate concentration on the coastal surface to be much higher than that on the open ocean. Once reached the surface, these phosphorus is rapidly absorbed and utilized by explosive phytoplankton communities, supporting the growth of lush diatoms and dinoflagellates, and promoting the prosperity of fishery food webs. At the same time, due to the extremely low oxygen content of rising deep water itself, coupled with the loss and decomposition of phytoplankton consumes oxygen (Figure 3) (Maßmig and Engel, 2021), it is easy for a large-scale hypoxic or even anaerobic environment (commonly known as "dark zones") to form a large-scale hypoxic or even anaerobic environment (commonly known as "dark zones") on the bottom of the coast. Under such conditions, reducing dissolution of iron in the sediment results in the release of large amounts of phosphorus back into the water. The study found that the concentration of water phosphate in the bottom layer of the offshore oxygen-deficient sea areas in Peru is several times higher than that in normal aerobic sea areas. Some of these phosphates continue to return to the surface with the upflow, forming a positive feedback of "hypoxia-regenerated phosphorus supply"; the other part of the phosphorus combines with the upsurge of sulfides in the sediment to form minerals such as apatite, achieving permanent burial (Glock et al., 2020). Figure 3 Percentage of the dissolved amino acids glycine (Gly) (a) and leucine (Leu) (b) and the dissolved combined carbohydrates glucose (Glc) (c) and galactose (Gal) (d) over depth for all stations sampled during the cruises M136 and M138 sorted by distance from shore. Insitu oxygenconcentrations are indicated with white contour lines (Adopted from Maßmig and Engel, 2021) 5 P Bioavailability and Limiting Effects 5.1 The ecological significance of phosphorus as a restricted nutrient In the ocean, macronutrient elements mainly include nitrogen, phosphorus, silicon, etc., where nitrogen or phosphorus is usually the bottleneck nutrient that limits primary productivity. The classic Redfield ratio (C:N:P = 106:16:1) points out that the average demand for nitrogen and phosphorus in phytoplankton is 16:1, so when N/P is significantly higher than 16 in the environment, phosphorus is often shortened, and vice versa. In many tropical
RkJQdWJsaXNoZXIy MjQ4ODYzNA==