Gilles Ledent

Heavy metals in Posidonia oceanica and Paracentrotus lividus from seagrass beds of the north-western Mediterranean

Abstract The concentration of Zn, Pb, Cd, Fe, Cr, Cu and Ti were measured in specimens of the seagrass Posidonia oceanica and the echinoid Paracentrotus lividus from three meadows in the N.W. Mediterranean (Marseille, France; Ischia, Italy; Calvi, Corsica). The concentrations of Hg were measured in the same echinoid specimens. Investigated metals are selectively distributed in the compartments of both species (i.e. the leaf-epiphyte complex, rhizome and root; and the digestive wall, gonads and body wall). Concentrations of most metals significantly differ in both the seagrass and the echinoid according to the considered meadow. These differences are of low amplitude except for Fe, Ti, Cu and Hg. Contaminations by these four metals show significant departures from background concentrations in Ischia biotas. Contamination by Pb differs from the background levels in both species in the three sampled sites.

Allometry of heavy metal bioconcentration in the echinoid Paracentrotus lividus

The relationships between concentration and size in Paracentrotus lividus were studied for seven metals (Zn, Pb, Cd, Fe, Cr, Cu, and Ti). In the calcified body compartment, Zn concentrations showed inverse power relationships, while concentrations of Pb, Cd, and Cr increased as power functions of echinoid size; Fe, Cu, and Ti concentrations did not vary significantly with echinoid size. In the non-calcified body compartment of the echinoid, the concentrations of Zn, Pb, Fe, Cu, and Ti showed inverse power relationships, Cd concentrations increased linearly, and Cr concentrations did not show any significant relationship with echinoid body size. Most relationships were rather weak, except in the cases of Pb and Fe in the non-calcified compartment and Cd in the calcified compartment. The allometric relationships were affected by seasonal factor in the non-calcified compartment only. The results indicate that biomonitoring programs using P. lividus as an indicator of metal contamination must take into account both echinoid size and season as source of metal concentration variations.

Element losses following distilled water rinsing of leaves of the seagrass Posidonia oceanica (L.) Delile

Rinsing of seagrasses with distilled water is often carried out prior to element analysis. The present study shows that such rinsing of the leaves of the Mediterranean seagrass Posidonia oceanica (L.) Delile results in significant element leakages, depending on leaf age. In adult leaves, only Fe concentrations are reduced. In younger leaves, significant concentration reductions occur for S, Mg, Na, Zn, Pb, Cd, Fe, Cr, and Ti, while concentrations of N, P, Ca, and Cu remain unaffected. C and K concentrations increase following distilled water rinsing owing to weight loss by leaching of Na and probably other major ions. The relative contribution of the different age classes to total shoot weight implies that distilled water rinsing also affects element analysis of whole shoots. The use of distilled water rinsing prior to element analysis should thus be avoided.