title: Impact of Organic Contamination on Some Aquatic Organisms.
abstract: 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.
  
  
  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.
  
  
  CONCLUSIONS
  Fish and D. magam were sensitive to low concentrations. These data suggest potent threats to aquatic organisms from organic contamination.
authors: Department of Environment and Earth Science, Faculty of Science, The Islamic University, Gaza, Palestine.
authors: El-Nahhal
authors: el-N
authors: Yasser
authors: Department of Environment and Earth Science, Faculty of Science, The Islamic University, Gaza, Palestine.
authors: El-Najjar
authors: el-N
authors: Shawkat
authors: Department of Environment and Earth Science, Faculty of Science, The Islamic University, Gaza, Palestine.
authors: Afifi
authors: A
authors: Samir
keywords: Carbaryl; Daphnia magna; chlorpyrifos; diuron; fish; mixture; toxicity