Phosphorus biogeochemical cycling in intertidal surface sediments from the Maowei Sea in the northern Beibu Gulf

Abstract

Surface sediments from 23 stations within the Maowei Sea intertidal flat were sampled for phosphorus (P) species analysis in December 2016. Different P forms were separated and quantified by a sequential extraction procedure. Results showed that the concentrations of total P (TP) ranged from 4.06 to 33. 33μmol g−1, and inorganic P (IP) was the predominant chemical form of TP. Fe-bound P was the main chemical form of IP. Terrestrial inputs, biological processes, and particle size were responsible for the distribution characteristics of different P species. In addition to detrital P, regeneration and transformation occured among different P forms in the intertidal surface sediments. The principal component analysis reflected the importance of organic matter in the binding of various P species to fine-grained sediments. Sedimentary organic carbon to P ratios were > 106, and suggested that organic matter in the intertidal sediments were mainly derived from terrestrial sources or contain mostly reworked organic matter. Organic carbon to reactive P ratios were 29−90, suggesting efficient sequestration of inorganic P in sediments. Potential bioavailable P represented a significant proportion of the sedimentary P pool, accounting for 70.0−95.9% of TP in the intertidal surface sediments and potentially contributing substantial amounts of reactive P to the overlying water column, especially in high organic and reducing sedimentary environments.