Role of Resuspended Sediments As Sources of Dissolved Inorganic Phosphorus along Different Dimensions in the Subei Shoal, South Yellow Sea, China

Several studies have documented that during ‘green tide’ events, comprising green macroalgae blooms in aquatic ecosystems, dissolved inorganic phosphorus (DIP) levels remain relatively steady despite the absorption of a large amount of DIP. In this study, surface sediment samples and a sediment core were extracted using a modified sequential extraction scheme, and water and surface sediment samples were analyzed in April 2017 to better understand phosphorus (P) cycling and replenishment in Subei shoal. We used a simple model on equilibrium of adsorption-desorption to present the buffering capacity of phosphate. The total P (TP) in the surface sediments ranged from 12.2 to 28.4 µmol g−1 (average 15.5 µmol g−1) and was dominated by inorganic P. TP, exchangeable P, reactive and reductive Fe/Al bound P, and authigenic apatite P significantly decreased northward and eastward from Subei shoal, contrary to the detrital P and organic P results. Dissolved and particulate inorganic P in the water samples ranged from 0.01 to 0.54 µmol L−1 (average 0.19 µmol L−1) and 0.9 to 19.6 µmol g−1 (average 4.9 µmol g−1), respectively. The applied model showed that suspended particulate matter is an important regulator of DIP behavior. Thus, modification of SPM can alter the DIP buffering capacity. The calculated buffering capacity in the surface layer of the sea water was > 60 within Subei shoal and always > 10 along the path of floating Ulva prolifera, providing a reasonable explanation for the steady concentration of DIP and its replenishment during the blooming of this green macroalgae.