Nitrogenous compounds and alkalinity patterns in Penaeus vannamei nurseries and pre-grow-out with low salinity water and synbiotic system: a case study

Abstract

This study aimed to evaluate the effect of different management strategies on the toxic nitrogen compounds and alkalinity patterns in nurseries and pre-grow-out of Penaeus vannamei culture with low salinity water (2.5 g L⁻¹) and synbiotic system. A study case is presented using three individual experiments (E): two nurseries (EI and EII: 2000 shrimp m⁻³ or 600 shrimp m⁻²) and one pre-grow-out (EIII: 300 shrimp m⁻³ or 90 shrimp m⁻²). Key water quality management strategies included the adoption of artificial substrate and water reuse with a microbial-based synbiotic system. In EI experiment, mean TAN was less than 0.50 mg L⁻¹ throughout the culture, NO₂⁻-N reached a maximum concentration of 0.80 mg L⁻¹, and NO₃⁻-N showed a decrease over the time. In EII, mean TAN was 0.64 mg L⁻¹ with a peak on day 10 of the experimental course, with the same pattern occurring for NO₂⁻-N. On the other hand, NO₃⁻-N constantly increased from 0.10 mg L⁻¹ at the beginning to 2.32 mg L⁻¹ at the end of the trial. In EIII, mean TAN was less than 0.50 mg L⁻¹ reaching a maximum concentration of 0.93 mg L⁻¹; NO₂⁻-N reached a maximum mean concentration of 0.70 mg L⁻¹ at the end of the experiment. NO₃⁻-N had a mean of 1.50 mg L⁻¹ at the beginning of the experiment and a reduction to 0.53 mg L⁻¹ at the end of the trial. Alkalinity showed mean concentrations of 114.90 mg L⁻¹, 88.04 mg L⁻¹, and 88.27 mg L⁻¹ for EI, EII, and EIII, respectively. The results demonstrated that the proposed management protocols adopted in EI, EII, and EIII were efficient for toxic nitrogen control in culture conditions using low salinity water and synbiotic system.