Aquatic ecosystems face variable exposure to pesticides , especially during floodings which are associated with short bursts of high contaminant concentrations that influence biological systems. An experiment was carried out using indoor experimental channels (artificial streams) to assess the long-term effect (20 days) of insecticide on periphyton communities exposed to low levels of Endosulfan (0.25,0.50 and 100 μg Lˉ¹).The effects of endosulfan on community biomass were assessed by measuring dry mass, ash-free dry mass (AFDM), chlorophyll a and autotrophic index (AI) factors. In artificial streams with endosulfan, there was a significant (p <0.05) reduction of chlorophyll a, dry mass and AFDM and increased (AI ), compared to controls with low endosulfan. These observations suggest that biomass of periphyton community could serve as an indicator of endosulfan pollution.