Relationships between sediment physico-chemical characteristics and heavy metal bioaccumulation in Mediterranean soft-bottom macrophytes

Concentrations of Hg, Cd, ph and Zn in the two seagrasses (Posidonia oceani ca and Cymodocea nodosa), green alga Caulerpa prolifera and sediment and so me physico-chemical characteristics of the sediment (organic matter, fine f raction (particles <63 <mu>m), carbonates and cation exchange capacity (CEC )) were quantified in a field study along the Mediterranean Spanish coast. Significant correlations between the concentrations of metals in the plants and sediment (alone or normalized with respect to the physico-chemical cha racteristics) were usually found for Hg and Zn. For Pb only C. prolifera fr actions were correlated to the Pb content of the sediment. For Cd no signif icant correlations were obtained between the metal in the plants and sedime nt. The concentration factors of the metals in the plants with respect to sedim ent were usually negatively correlated with the fine fraction, organic matt er and CEC of the sediment for Hg, Pb and Zn in Posidonia and Cymodocea, an d for Hg and Zn in Caulerpa. This suggests that these variables of the sedi ment increase the retention of these metals in the sediment and reduce thei r availability to the plants. Stepwise multiple regression analyses yielded only three equations with at least two independent variables in the model: the Hg concentration in leave s and roots of Posidonia oceanica is explained by the Hg concentration of t he sediment and organic matter of the sediment. The Hg concentration in the fronds of Caulerpa prolifera is explained by the Hg concentration in the s ediment and by the carbonate content of the sediment. (C) 2001 Elsevier Sci ence B.V. All rights reserved.