Effect of low salinity on acute arsenic toxicity and bioconcentration in shrimp Litopenaeus vannamei juveniles

Abstract

This study investigated acute arsenic toxicity and bioconcentration capacity in Litopenaeus vannamei because it has been frequently exposed to lower salinities than its isosmotic point (25 g L^-1). Juveniles (9.9 ± 0.4 g) were exposed to low (5-10 g L^-1) and isosmotic salinity (25 g L^-1) levels; As values were 30.8, 20.2, 16.8 and 13.9 mg L^-1 at 5 g L^-1; 30.4, 19.1, 16.8 and 14.8 mg L^-1 at 10 g L^-1; 31.5, 19.0, 15.0 and 11.9 mg L^-1 at 25 g L^-1 at 24, 48, 72 and 96 h LC₅₀, respectively. No significant differences were found among As LC₅₀ values calculated for different salinity levels and same exposure times, concluding that low salinity did not affect shrimp sensitivity to As. Likewise, no significant differences were observed in As bioconcentration in shrimp exposed to the same waterborne As and distinct salinity, supporting the results of acute toxicity. Bioconcentration factors of As maintained a relatively stable tendency where all values (0.8 ± 0.2 to 1.7 ± 0.4) were statistically comparable to 1, indicating that As was accumulated in a similar proportion to waterborne As concentration at three salinity levels. This study proposed 135.3 ± 12.1 μg L^-1 for salinities from 5 to 25 g L^-1 as provisional safe As concentration. According to these results, the hypothesis that sustains an effect of low salinity on As acute toxicity and its bioconcentration capacity cannot be acceptable. Therefore, the information provided allows knowing the threshold levels of As in water to avoid ecological and economic losses.

Keywords: Acute toxicity; Arsenic; Bioconcentration; Low salinity; Shrimp.