Abstract: Investigation of this region reveals that the concentrations of inorganic nitrogen and petro-products in the sea water ranged between Grades Ⅱ and Ⅲ of the standards for sea water quality;and the concentration of inorganic P was well exceeding Grade Ⅳ of the standards.The quality of the substrate of the shoals fitted well into Grade I of the standards for maritime deposit quality by and large,but PCBs in some sampling sites was found beyond the limit of Grade V.A total of(2 976) strains of bacteria were isolated under 17 genera and some genera of enterobacteriaceae,separately,showing apparent features of their terrestrial sources.A total of 71 species of planktons were collected.Most of them belong to euryhalin Bacillariophyta,and may be used as the food for shellfish.The residues of petro-products,Cd,Cr,Hg,Cu and PCBs in the body of some shellfish were found well beyond the limit of the standards for maritime shellfish quality to a varying degree.Based on the relationship observed between the environment and shellfish culturing on the beach,some approaches and ways were suggested for making overall plans that take all factors into due consideration so as to improve the environment of the shoals as well as shellfish cultivation.

Key words: shoal, shellfish, heavy metal, petro-products, PCBs