Linking metal bioavailability and biological effects: a case study in the Venice Lagoon, Italy

It is now almost universally recognized that the most effective bioindicators in marine environment are those native organisms not only physiologically suitable and ecological relevant, but also site-specific. In this context, it may be provided the most reliable information about contaminants both in term of bioavailability and effects, thus predicting potential damages at higher ecological level, and contributing ultimately to evaluate the potential environmental and human health threats. In this research work we focused on the polychetes Hediste diversicolor and Perinereis cultrifera, two of the most common infaunal benthic invertebrates in the intertidal confined estuarine habitats in the Lagoon of Venice, Italy. The aims were to investigate the potential use of these species in highlighting environmental stress effects, thus contributing to the risk evaluation procedures to be used in the management of this area. Four seasonal samplings were carried out in two differently impacted sites of the Lagoon and these chemical and biological parameters were determined in the whole organism tissues: Cu, Cd, Cr, Mn, Pb, Zn, metallothioneins and malondialdehyde (MDA). Body burden results of heavy metals, referred to the sediment bioavailability (determined by diluted HNO3 treatment) of the same contaminants, revealed higher BSAFs and a correspondent stronger relationship between bioaccumulation and sediment bioavailability in Hediste than in Perinereis, highlighting at the same time the worst fit of the correlation in Perinereis from the most contaminated site. Differently, MDA levels evidenced the expected trend of stress in relation to the sediment bioavailabilty for both Hediste and Perinereis, Hediste from the most polluted site resulting the most stressed, and Perinereis from the less polluted site the less stressed. As for metallothionein content, no significant differences were detected between organisms, nor between sites.