Biomonitoring of Metal Availability in the Southern Basin of the Lagoon of Venice (Italy) by Means of Macroalgae

Abstract

Macroalgae of the following species: Ulva laetevirens, Enteromorpha intestinalis, Gracilaria verrucosa and Sargassum mutycum, were used to monitor metal concentrations (Al, Mn, Fe, Cu, Zn, Cr, Co, Ni, Cd) in the waters of the southern basin of the Lagoon of Venice. Sampling was performed at 5 sites, gradually moving north from the town of Chioggia. Species-specific seasonal variability was observed, with significant increases of Cd in U. laetevirens in January,Al and Pb in E. intestinalis in May, and Al and Ni in S. mutycum in January. Seasonal relative frequencies of metalpeak concentrations emphasize the occurrence of Pb peaks in May for all the studied species. Analysis of inter-site variability shows significant increases of Al, Fe, Cr and Pb in U. laetevirens at the Hydro-Biological Station, located within the town of Chioggia. Metal concentrations in algae are comparable with those in other areas of the lagoon, although Fe, Cr and Ni concentrations are lower than in the northern and central basins.This result fits dissolved metal concentrations determined byother authors, but does not correspond to the reported presence ofCr in the sediments of the southern basin. The hypothesis isdiscussed according to which low Cr levels in algae reflect Crspeciation in sediments.