This investigation was aimed to evaluate water pollution with heavy metals using three biomarkers, as well as the study of the aquatic insects-seasons interaction. Three species of aquatic insects collected from El-Mansouriya stream (Dakahlia, Egypt), during the different seasons from spring 2014 to winter 2015. Water samples, sediments and whole body of the three aquatic insects were analyzed for heavy metal contents. As well as, two enzyme biomarkers, Acetylcholinesterase (AChE) and glutathione-S-transferase (GST) were used to monitor aquatic insects' response to water pollutants. Results showed various activities of the three biomarkers at the different studied seasons. Where, the concentration of selected heavy metals, in the whole body of the three insects, showed a relatively wide range for each metal analyzed. Also, higher values of metal pollution index (MPI) were attained in hotter seasons (spring and summer) and its decrements were observable during cooler seasons (autumn, winter), that provides a representative picture to the environmental state of environmental impacts on the aquatic ecosystem. While the heavy metals were found to be highly accumulated in selected aquatic insects body, as well as the variation of enzymes activity, thus both enzymes could be used as biomarker of water and sediment contamination.

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