Concentrations of trace metals (Cd, Cu, Fe, Pb) in Posidonia oceanica seagrass of Liscia bay, Sardinia (Italy)

Heavy metal concentrations were measured in Posidonia oceanica seagrass from a Mediterranean site (Liscia bay, N Sardinia, Italy) in order to assess the degree of metal pollution in the area. Metals Cd, Cu, Fe and Pb were measured in sheaths and rhizomes dated and dissected by lepidochronology procedures, which may offer a timeseries of metal concentrations in the environment (Pergent 1990; Romeo et al. 1995). Comparison between metal concentrations according to lepidochronological years in sheaths and rhizomes produced significant differences: Cd and Cu concentrations were similar in the two tissues, while Fe and Pb showed higher values in sheaths, with differences up to 2 orders of magnitude. Rhizome concentrations showed no trend related to lepidochronological years, whereas Cu, Fe and Pb tended to decrease over time in sheaths. Values detected in sheaths and rhizomes of P. oceanica from Liscia bay were generally low, compared with other Mediterranean sites, with the exception of Fe: this confirms that the site is a clean area without anthropogenic enrichment and with metal concentrations representing background values.