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Abstract I’ Heavy metals are considered the most insidious and dangerous category of pollutants in the sea which enter the aquatic environment from both natural and anthropogenic sources. Once added to the environment they are not readily. converted into something harmless. Metal contamination of aquatic environment may lead to deleterious effects from localizedinputs which may be acutely or chronically toxic to aquatic life withinthe effected area. Most published data on the effects of metals on aquatic organisms, however, report adverse effects at concentrations higher than usually found in the environment. Metals are often accumulated in tissues of organs which have taken them up, and this leads to an amplification of their concentration in animals higher up in food chain.Man as a carnivore at the top of many marine food chains, therefore is exposed to the risk of taking a diet enriched by these substances, and severalmetals are accumulative poisons, causing serious effect on the humanhealth. The present work is devoted for a detailed study on the levels and distribution of heavy metals (Zn, Cu, Pb and Cd) in waters and sediments at different sites along the coast of Alexandria. The variation in concentrations and the distribution of these heavy metals in the tissues of commercial crustaceans, bivalves and fish species collected from different sites along the Alexandria coastal waters were also investigated and discussed. This thesis comprises five chapters, the first chapter is a review for the heavy metals in the aquatic environment and a review of the previous. |