Toxicity of pesticides on photosynthesis of diatoms

Pakistan being an agricultural country,a large amount of pesticides are used,including organophosphates and synthetic pyrethroids. these pesticides are released through rivers and other tributeries into the coastal environment,thus posing a contiuous threat to marine organisms. in the present study two species of diatoms amphora and navicula were selected for the assessment of impact of organphosphate and pyrethroid toxicity on these primary producers. the study shows that rate of photosynthesis was inhibited in both amphora and navicula species exposed to pesticide. the acute toxicity of pesticide was determined by measuring ic50 of the test organisms. ic50 calculated for diatom species depicts that different pesticides had variable effects on the photosynthesis of microalgae. high sensitivity of marine organisms is alarming as it may have implications on the marine ecosystem and fisheries. the results are also useful in setting control limits for the release of these chemicals in nature.