U. S. Copyright Clearance Center Code Statement: 0173-9565/02/S2301±138$15.00/0 Monitoring a Marine Coastal Area: Use of Mytilus galloprovincialis and Mullus barbatus as Bioindicators Ilaria Corsi*, Michela Mariottini, Valentina Menchi, Christiana Sensini, Cristiana Balocchi, Silvano Focardi Dipartimento di Scienze Ambientali, Universita Á degli Studi di Siena, Via delle Cerchia, 3 53100-Siena, Italy. With 4 figures and 4 tables Keywords: Fish, mussel, contamination, biomarkers, gonad histology. Abstract. Samples of Mytilus galloprovincialis and Mullus barbatus were collected in eight coastal sites along the South Adriatic and Ionic coasts of Italy in spring 2000 for a survey of coastal pollution in the Mediterranean basin. Specimens were analysed using an integrated approach based on residue analysis of common aquatic pollutants like or- ganochlorines such as hexachlorobenzene (HCB), DDTs and polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), heavy metals and nonylphenols (NPnE) and biomarker responses such as acetylcholinesterase (AChE) activity, and the two specific P450 activities benzo(a)pyrene monooxygenase (BPMO) and 7-ethoxyre- sorufin-O-deethylase (EROD). Biological and morphological parameters like somatic liver index (SLI), gonadosomatic index (GSI) and gonadal and gamete histology (eggs and sperms) were also evaluated in red mullet samples. A contamination gradient in whichseveralhotspotsoccurwererevealedinthisstudy.Thehotspotsaccountforhigh levels of organochlorines in both species near incinerators and of PAHs in harbour areas. Levels of both NPnE and AChE activity were highest in two protected marine areas and were within detectable limits in others. This finding was confirmed by P450 activities, in which maximum levels were detected in harbours and protected marine areas. No morphological alterations of male and female gonads were observed on the histological level. Problem Aquatic ecosystems serve as a sink for pollutants, which bind to sediment and tend to accumulate in the tissues of aquatic organisms. Marine coastal areas are extremely im- pacted by human activities, thus better reflecting the health of the overall marine eco- P.S.Z.N.: Marine Ecology, 23, Supplement 1 (2002), 138±153 Ó 2002 Blackwell Verlag, Berlin ISSN 0173-9565 * Author to whom correspondence should be addressed: corsii@unisi.it