Single and mixture toxicity of As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn to the rotifer Proales similis under different salinities.

Abstract

Aquatic organisms that inhabit coastal environments are generally exposed to multiple mixtures of chemicals. The single and mixture toxicity of nine trace metals (As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn) to the rotifer Proales similis were examined at four different salinities (5, 15, 25, and 35ppt). Chronic toxicity reproductive tests were performed using an application factor (AF) of 0.05, 0.1, 0.2, and 0.4 by multiplying the 24-h LC50 values of each metal. The metal mixture treatments were: T1, As-Cd-Cr-Cu-Fe-Hg-Ni-Pb-Zn; T2, As-Cd-Hg-Pb and; T3, Cr-Cu-Fe-Ni-Zn. The LC50 values ranged between 5 and 4140μgL-1 in the following order: Hg>Cu>Fe>Pb>Cd>Zn>As>Cr>Ni in low salinity and Hg>Cu>Fe>Pb>Zn>As>Cd>Cr>Ni in high salinity conditions. In all cases, acute toxicity was higher at a salinity of 5ppt compared to 35ppt. Chronic toxicity tests indicated that single metal toxicity intensified as the AF increased and as salinity decreased. Regardless of salinity, Pb at 0.4 AF was the most toxic metal. Proales similis evidenced a higher growth in the As treatments (0.1 and 0.2 AF) at 35ppt compared to controls. Furthemore, the T1 and T2 treatments were the most toxic, and in most cases, they induced a synergistic effect. Antagonism effects were detected in the T3 treatment at 25 and 35ppt. The present data highlights the importance of the examination of pollution in natural environmental conditions in which many aquatic invertebrates endure.