الفهرس 
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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.