الفهرس 
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Abstract
The Burullus Lake is one of the stressed wetlands on the Egyptian Mediterranean coast, receiving different types of discharges which are loaded by industrial as well as domestic and agricultural wastes. The polychaete Hediste diversicolor was the dominant invertebrate in the soft sediment of Lake Burullus and it was, therefore, selected as a biomarker to evaluate the levels of some heavy metals (Cd, Cu, Pb, and Zn) and Malathion the commonly used pesticide. The study was carried out on worms collected monthly from a fixed station near the lake’s coast. The concentration of the four heavy metals and Malathion were measured in the worms and the sediment monthly from September 2018 to September 2019. Also, some laboratory experiments were performed to assess the capacity of the worm to release as well as bioaccumulate the metals and the Malathion; and to detedt the mortality of worms under the effect of both types of pollutants. The results indicated wide variation in the contents of heavy metals in the sediment and worms, with mostly higher concentration in the worms. The worms displayed high capacity for metal bioaccumulation, particularly Cu and Pb, against low rate of metal release. Both metals showed similar mortality rate to the test-worms (51.7% and 51.6%, respectively) at 500 µ/l after 7 days for each metal.