The impact of fish farming on phosphorus loading of surface sediment in coastal complex aquaculture

The horizontal distributions of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in the surface sediments where complex aquaculture is conducted in Shido Bay, Seto Inland Sea, Japan, were determined to investigate the impact of fish and oyster farming. We also determined five fractions of phosphorus in the surface sediments. Relatively high phosphorus contents (P/C ratios) were observed in fish farming areas, likely due to the waste feed and fecal matter. Moreover, relatively high abundances of the Ca-bound P (Ca-P) and detrital P (Ref-P) fractions were observed in fish farming areas, likely due to bones of small fish used as feed. Our results strongly suggest that the P/C ratio and the Ca-P and Ref-P fractions in the surface sediments are good indicators of the effects of fish farming and allow its characterization, and are particularly valuable in the area of complex aquaculture.