Iron, zinc, copper, lead and cadmium contents in Ruppia maritima from a Mediterranean coastal lagoon: monthly variation and distribution in different plant fractions

Abstract

Abstract Metal concentrations and quantities were determined monthly in different fractions of the submerged angiosperm Ruppia maritima in Monolimni Lagoon, Aegean Sea. Concentrations were the highest in the roots, suggesting that the sediment-to-root pathway is a principal uptake route of metals. Most metals were equally distributed between rhizomes plus stems and leaves; Fe accumulated greatly in the rhizomes plus stems, whereas Cu occurred mostly in the leaves. Positive correlations were found between metal concentrations in different plant parts, suggesting metal translocation. Most metal concentrations in the different parts declined during the growing season. Iron and Cd accumulation was found to be associated with temperature, which strongly influences the plant growth; additionally, Fe and Cd concentrations in plant tissues were negatively correlated with leaf, rhizome plus stem biomass. Copper concentrations in the roots showed a converse monthly pattern. No metal concentration in plant fractions was positively correlated with concentrations in the water or sediments. Metal quantities (μg m-2) stored in the plant generally increased 2- to 4-fold during the growing season. Evidence that return to sediments is a major fate of these quantities is provided by the seasonal pattern in sediment metal concentrations.