HEAVY-METALS IN SEDIMENTS, SPM AND PHYTOZOONBENTHOS OF THE LAGOON OF VENICE

Heavy metal concentrations were measured in the surface sediment, the settled particulate matter (SPM), the macroalgal biomass and some zoobenthic taxa of three areas (Alberoni, Sacca Sessola and S. Giuliano) spanning the main bio-geo-physico-chemical differences of the central lagoon of Venice. In terms of average metal content the observed contamination indicates the following sequence: SPM>sediment>macroalgae>zoobenthos. The dominant macroalgal species in the central lagoon of Venice, that is Ulva rigida C.Ag., showed a preferential enrichment of Zn and Mn compared to other metals. Both seasonality and frond age were responsible for the heavy metals found in the macroalgae. Finally, considering the amount of metals involved in the total gross primary production (GPP) and the total heavy metal quantity flowing into the central lagoon by streams and rivers, in situ turnover is thought to take place.