Acute toxicity of nitrite on white shrimp <i>Litopenaeus vannamei</i> (Boone) juveniles in low‐salinity water

Abstract

The nitrite toxicity was estimated in juveniles of L. vannamei. The 24, 48, 72 and 96 h LC50 of nitrite-N on juveniles were 8.1, 7.9, 6.8 and 5.7 mg L−1 at 0.6 g L−1; 14.4, 9.6 8.3 and 7.0 mg L−1 at 1.0 g L−1; 19.4, 15.4, 13.4 and 12.4 mg L−1 at 2.0 g L−1 of salinity respectively. The tolerance of juveniles to nitrite decreased at 96 h of exposure by 18.6% and 54.0%, when salinity declined from 1.0 to 0.6 g L−1 and from 2.0 to 0.6 g L−1 respectively. The safe concentrations at salinities of 0.6, 1.0 and 2.0 g L−1 were 0.28, 0.35 and 0.62 mg L−1 nitrite-N respectively. The relationship between LC50 (mg L−1), salinity (S) (g L−1) and exposure time (T) (h) was LC50 = 8.4688 + 5.6764S – 0.0762T for salinities from 0.6 to 2.0 g L−1 and for exposure times from 24 to 96 h; the relationship between survival (%) and nitrite-N concentration (C) for salinity of 0.6–2.0 g L−1, nitrite-N concentrations of 0–40 mg L−1 and exposure times from 0 to 96 h was as follows: survival (%) = 0.8442 + 0.1909S – 0.0038T – 0.0277C + 0.0008ST + 0.0001CT–0.0029SC, and the tentative equation for predicting the 96-h LC50 to salinities from 0.6 to 35 g L−1 in L. vannamei juveniles (3.9–4.4 g) was 96-h LC50 = 0.2127 S2 + 1.558S + 5.9868. For nitrite toxicity, it is shown that a small change in salinity of waters from 2.0 to 0.6 g L−1 is more critical for L. vannamei than when wider differences in salinity occur in brackish and marine waters (15–35 g L−1).