POSIDONIA-OCEANICA - A BIOLOGICAL INDICATOR OF PAST AND PRESENT MERCURY CONTAMINATION IN THE MEDITERRANEAN SEA

Concentrations of mercury were measured in various tissues of Posidoni a oceanica seagrass at three sites presenting distinct degrees of huma n activity. The accumulation of mercury differed according to the tiss ue examined and the level of contamination of the sire. Mercury concen trations recorded at Calvi ranged from 10.0 ng g(-1) dry weight in bla des to 30.1 ng g(-1) in rhizomes, whereas at Marseilles-Cortiou, the r ange was between 52.3 ng g(-1) in rhizomes and 176.5 ng g(-1) in blade s. The use of lepidochronology, a technique for dating the dead sheath s and rhizomes of P. oceanica, rendered it possible not only to determ ine the present level of contamination at each site, but also to recon stitute the patter of change in the degree of contamination of the env ironment over a period of twenty years. P. oceanica is considered to b e an accurate bioindicator of past and present mercury contamination. (C) 1998 Elsevier Science Ltd. All rights reserved.