Nitrate level safety to Amazon River shrimp juveniles

The study's objective was to evaluate the nitrate level safety for Macrobrachium amazonicum juvenile in the laboratory, a potential native species for culture in Brazil. The experiment consisted of six treatments with six replicates in a completely randomized block design: 0, 250, 500, 1,000, 1,500, and 2,000 mg L^-1. Physical and chemical water quality parameters were recorded every 12 h, while the shrimp mortalities in the 24-h interval. Except for nitrate, all physical and chemical water quality parameters remained within the ideal range rearing to this species. No deaths were observed during the first 6 h of exposure range 0-500 mg L^-1 concentrations. At 250 mg L^-1 N-NO₃^-, the mortality (10%) started from 48 h. At 500 mg L^-1 N-NO₃^-, shrimp mortalities occurred after 24 h, reaching 60% after 72 h. In the treatments with 1000 and 1500 mg L^-1 N-NO₃^- concentrations, dead shrimps can be observed after 24 h, with a mortality rate of 78% and 90% of the population in 96 h, respectively. All shrimps exposed at 2000 mg L^-1 died in 96 h. The LC50 values obtained decreased with increasing exposure time. Based on LC50 (96 h), the N-NO₃^- level safety to M. amazonicum is 48.5 mg L^-1.