Evaluating nutrient transformation and fate in the recirculating aquaculture system of Apostichopus japonicus and its environmental impact from a diet perspective

Sammendrag

The accumulation of nitrogen (N) and phosphorus (P) pollutants elevates the water treatment load and cost of recirculating aquaculture system (RAS) for Apostichopus japonicus, thereby restricting its development. So, this study sought to evaluate the effects of feed ratios on water quality, nutrients fate, and gut microbiota within A. japonicus RAS. The mass ratios of commodity feed and sea mud were 1:1, 1:2, 1:3, 1:4, 1:5, respectively. The results showed that nutrients accumulation occurred in all treatments during the late stage of culture. Most of N and P were lost through sediments (N: 88.25–95.93 %, P: 92.67–94.26 %) and biomass harvesting (N: 2.48–8.53 %, P: 0.21–1.94 %). The sediment accumulation of N and P in group 1:4 was the highest, while that in group 1:3 was the lowest. A significant correlation was found between environmental factors and gut microbiota (P < 0.05). The concentration of NH4+-N was negatively correlated with the abundance of probiotics, such as Ruegeria. Correlation analysis between TN and sediment contents also revealed the contribution of sediment accumulation on water quality. Overall, the N and P in group 1:3 were most utilized and least lost, which exhibited better environmental and economic benefit.