Acute toxicity of nitrate on Pacific white shrimp，Litopenaeus vannamei，at different developmental stages

Pacific white shrimp，Litopenaeus vannamei，at different developmental stages were exposed to nitrate–N（nitrate as nitrogen）with different concentrations using the static renewal method in 15‰ salinity. The results showedthat median lethal concentrations（LC50） of nitrate-N for L. vannamei were positively correlated with exposure time.However，it was different to the shrimps at different developmental stages. The 24-，48-，72-，96-h LC50 of nitrate–N for L. vannamei were 1 534.64，957.64，538.77，189.32 mg/L with body length of 1（±0.15）cm；2 999.71，2 092.26，1 591.49，1 077.32 mg/L with body length of 3.47（±0.45）cm；2 379.55，2 202.34，1 781.26，1 314.49 mg/L with bodylength of 5.17（±0.58）cm；2 648.34，1 515.83，702.63，494.85 mg/L with body length of 10.20（±1.45）cm，respectively.The safe concentrations for rearing L. vannamei were estimated to be 18.93，107.73，131.45 and 49.48 mg/L nitrate–N inthose four development stages，respectively.