ABSTRACT
Trace metals are directly toxic to aquatic organisms and are also significantly accumulated by many marine and estuarine species. Marine and estuarine macroalgae have long been known to concentrate metals to levels many times those found in the surrounding waters. Monitoring programs are required to establish both spatial and temporal trends in metal abundance and bioavailability in estuaries and other coastal waters. The use of an aquatic organism as bio-monitor of metals in coastal waters is defensible only when the resulting picture of environmental contamination truly reflects ambient metal bioavailabilities. Perhaps the most important property of a bio-monitor is that it must not regulate the accumulated levels of pollutants in its body or tissues. Several extraneous factors are known to influence the concentrations of metals present in gastropod mollusks, and these should be considered if such species are to be employed as bio-monitors.
