Impact of Organic Contamination on Some Aquatic Organisms

Background: Contamination of water systems with organic compounds of agricultural uses pose threats to aquatic organisms. Carbaryl, chlorpyrifos, and diuron were considered as model aquatic pollutants in this study. The main objective of this study was to characterize the toxicity of organic contamination to two different aquatic organisms. Materials and Methods: Low concentrations (0.0–60 μmol/L) of carbaryl, diuron and very low concentration (0.0–0.14 μmol/L) of chlorpyrifos and their mixtures were tested against fish and Daphnia magna. Percentage of death and immobilization were taken as indicators of toxicity. Results: Toxicity results to fish and D. magna showed that chlorpyrifos was the most toxic compound (LC₅₀ to fish and D. magna are 0.08, and 0.001 μmol/L respectively), followed by carbaryl (LC₅₀ to fish and D. magna are 43.19 and 0.031 μmol/L), while diuron was the least toxic one (LC₅₀ values for fish and D. magna are 43.48 and 32.11 μmol/L respectively). Mixture toxicity (binary and tertiary mixtures) showed antagonistic effects. Statistical analysis showed a significant difference among mixture toxicities to fish and D. magma. Conclusion: Fish and D. magam were sensitive to low concentrations. These data suggest potent threats to aquatic organisms from organic contamination.