Nutrient dynamics, environmental impacts, and feed efficiency in intensive whiteleg shrimp (Litopenaeus vannamei) farming on sandy soils in Ninh Thuan, Vietnam

Whiteleg shrimp (Litopenaeus vannamei) farming has expanded rapidly on sandy coastal soils in Vietnam’s South Central region. These permeable soils, combined with high feed input and limited waste treatment, raise concerns about nutrient pollution and environmental degradation. This study assessed nutrient dynamics and environmental impacts in a typical intensive shrimp pond system in Ninh Thuan province over a 66-day culture cycle. Physical, chemical, and biological parameters were monitored, including temperature, salinity, total suspended solids, chemical and biological oxygen demand, total nitrogen, total phosphorus, ammonium, microalgae composition, and bacterial counts. A nutrient mass balance showed that commercial feed contributed 81.9 % of total nitrogen and 87.8 % of total phosphorus inputs. However, nutrient utilization was low: only 13.8 % of nitrogen and 11.4 % of phosphorus were retained in shrimp biomass. The remaining nutrients were lost through multiple pathways: 23.2 % of nitrogen and 1.8 % of phosphorus in effluent, 10.3 % of nitrogen and 2.5 % of phosphorus in pond sludge, and over 50 % of nitrogen and 84 % of phosphorus unaccounted for due to volatilization, denitrification, and sedimentation. 1000 kg of shrimp harvested discharged approximately 263.6 kg of nitrogen, 5.02 kg of phosphorus, and 12,175 liters of nutrient-rich wastewater. Although sludge represented only 5 % of total discharged water, it carried a disproportionately high nutrient load, posing risks to soil, groundwater, and nearby coastal ecosystems. These results highlight critical inefficiencies in nutrient use and significant environmental risks. Effective strategies, including lower feed conversion ratio, improved feed management, and dedicated sludge and wastewater treatment systems, are essential for sustainable shrimp aquaculture on sandy soils.