Differential Response of Fresh Water Algae Ankistrodesmus acicularis and Anabaena flos-aquae to Dichlobenil Exposures

Abstract

The massive use of herbicides may harm the growth of algae, which in turn might disturb the balance of the aquatic ecosystem. Herein the physiological as well as the biochemical responses of two fresh water algae namely Ankistrodesmus acicularis (Chlorophyta) and Anabaena flos-aquae (Cyanobacteria) to different concentrations of dichlobenil were assessed. Parameters including chlorophyll (a) Chl (a) content, EC50 values, carbohydrate and adenosine triphosphate (ATP) contents as well as the uptake of dichlobenil by both algal species were tested. The results indicated that a significant decrease in chlorophyll (a) content of both algal species to intermediate and high concentration of dichlobenil, whereas stimulative effect of low concentration of dichlobenil on Chl (a) content were recorded. Attainable results derived by probits analysis revealed that the EC50 values for both algae at 5th and 7th days approximate each other. Additionally, drastic decrease (98%) in ATP content was observed at 8.0 mg/L dichlobenil treatment in case of Ankistrodesmus acicularis. Furthermore, Anabaena flos-aquae cells activity was enhanced by the application of low and intermediate concentrations of dichlobenil (0.25-4.0 mg/L). Higher concentration level (16.0 mg/L) led to relative decrease in ATP content. Ankistrodesmus acicularis was found to be more sensitive than Anabaena flos-aquae. The uptake of dichlobenil was best ascribed to a pseudo-first order rate kinetic. The specific uptake rate constants of dichlobenil in case of Ankistrodesmus acicularis were relatively lower than the corresponding rates exhibited by Anabaena flos-aquae. In sum, the uptake of dichlobenil by algae may present environmental hazards and could affect the human health, through accumulation in the food chain.