Effects of shrimp pond effluents on stocks of organic carbon, nitrogen and phosphorus in soils of Kandelia obovata forests along Jiulong River Estuary

Abstract Global aquaculture discharges are typical anthropogenic carbon and nutrient sources to nearby mangrove forests. In this study, we quantified total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) stocks (0–50 cm) in soils from three sites of Kandelia obovata forests with different shrimp-pond discharge histories of 0, 8 and 14 years (i.e. 0DK, 8DK and 14DK, respectively). Results showed that shrimp pond effluents increased soil TOC densities at 8DK. TP densities gradually increased with discharge histories, whereas TN densities were similar between 8DK and 14DK. Besides, IsoSource analyses demonstrated that the high δ13C values of shrimp pond effluents contributed 30.00%–33.60% of mangrove soil TOC at 0–10 cm depth. These results suggested that shrimp pond effluents altered soil TOC, TN and TP stocks and added carbon source to mangrove soils, which was related to discharge histories and soil depth. Moreover, the discharge changed carbon and nutrient patterns, which warrant attention.