Effects of stocking density on sediment quality and carbon, nitrogen, and phosphorus emission factors in bottom sediments of whiteleg shrimp ponds in Ninh Binh province

Abstract

This study aimed to assess the concentrations and emission factors of organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) in bottom sediments of three whiteleg shrimp (Litopenaeus vannamei) farming models with different densities in Ninh Binh Province, including: super-intensive (A, 219 ind./m²), super-intensive (B, 167 ind./m²), and intensive (C, 92 ind./m²). Sediment samples were collected using a specialised trap over four rearing periods (TN1-TN4). The results showed that OC, TN, and TP concentrations increased gradually with rearing time and were directly proportional to stocking density. At the end of the crop, model A recorded the highest values (OC: 4.00±0.32%; TN: 5,811±380 mg/kg; TP: 2,856±210 mg/kg), followed by model B (3.65±0.28%; 4,791±320 mg/kg; 2,026±150 mg/kg), and the lowest was model C (2.24±0.19%; 3,260±240 mg/kg; 1,530±110 mg/kg). The emission factor (F_i-bun) was highest in model A (OC: 6,468 kg/ha/crop; TN: 932 kg/ha/crop; TP: 439 kg/ha/crop). High stocking density increased the accumulation and emission of organic matter and nutrients in the sediment, thereby increasing environmental pressure.