Effect of Water Pollution by Organophosphate Pesticides on Seasonal Distribution of Freshwater Macrophytes and Snails in Egypt

Water pollution caused by pesticides is one of the urgent issues, especially in the developing countries. Organophosphate pesticides residues reach water canals through the discharge from agricultural fields. The aim of the present study was to assess the effect of water pollution caused by organophosphate pesticide residues on the aquatic life using macophytes and snails as indicators. The study was carried out along aover the course of a  year in Qalubeya Governorate, Egypt, where the samples were seasonally collected. The results indicated that fenamiphos, fenitrothion, diazinon, malathion and pirimiphos-methyl showed the highest concentrations in both water and sediment samples. Eichhornia crassipes and Lemna gibba were the highly represented macrophytes in the investigated canals, and the most widespread snail species was Physa acuta. The correlation analysis between different parameters indicated that diazinon and fenamiphosnegatively affected the population of the Lymnaea natalensis and P. acuta snails, whereasmalathion and phorate pesticides had negative effects on Succinea cleopatra. On the other hand, fenitrothion, prothiophos and pirimiphos-methyl showed positive correlations with each of the L. natalensis and P. acuta snails. For the relationships between the detected pesticides and macrophytes, it was found that diazinon and fenamiphos deleteriously affect the distribution of Azolla pinnata, Phragmites australis and Atropa belladonna. While fenitrothion, prothiophos and pirimiphos-methyl had negative effects on the distribution of E. crassipes and Echinochloa sp. Meanwhile, these two macrophyte species can tolerate high concentrations of diazinon and fenamiphos. In conclusion, water pollution with high concentrations of organophosphate pesticides can affect the population and distribution of macrophytes and snails, which subsequently affect the functioning of the aquatic ecosystem.