Acute Toxicity of Heavy Metals to Onchidium struma under Different Salinities

This study evaluated the acute toxicity of three heavy metals Cu, Hg and Cr(VI) to Onchidium struma juvenile. The results showed that 24 to 96 h median lethal concentration (LC50) values for Cu, Hg and Cr (VI) at 15 practical salinity units (psu) were 138.33-160.32, 6.88-9.41 and 144.47-218.97 mg/L, respectively. It demonstrated that O. struma was sensitive to three heavy metals: Hg > Cu > Cr (VI). Moreover, toxicity tests were conducted under different salinities (5, 15 and 25 psu) due to the seasonal salinity changes in habitat. For Cu, 96 h cumulative mortalities at 5, 15 and 25 psu salinity groups were 40, 70 and 85%, respectively. The 96 h LC50 values for Cu at 5 psu were much higher than those at 15 and 25 psu. For Hg, 96 h LC50 values were not statistically different along with salinity. For Cr (VI), 96 h LC50 values were significantly higher at 25 psu salinity group. These suggested that O. struma became more sensitive to Cu at higher salinity, and sensitive to Cr (VI) at lower salinity. The sensitivity of O. struma to heavy metals studied was related with the salinity. Safe concentrations for Cu, Hg and Cr (VI) were 13.78, 0.69 and 12.69 mg/L, respectively. This study provides useful information to detect environmental pollution under different salinities with this biomonitor O. struma. (C) 2019 Friends Science Publishers