This book collects different results of experiments conducted by several authors in order to clarify the role of bioindicator organisms, highly sensitive to environmental changes. In particular, invertebrates occupy a key position as intermediate consumers in the pelagic as well benthonic food of aquatic ecosystems. Then, aquatic organisms may represent excellent bioindicators of the health of the sea. The main purpose of monitoring the concentrations of heavy metals in biota is to determine the toxicological risk faced by organisms and even from the humans through the ingestion of...