The distribution of some metallic elements in eelgrass ( Zostera marina L.) and sediment in the Limfjord, Denmark

The distribution of Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Pb and Zn in different parts of eelgrass ( Zostera marina L.) and sediment (0–25 cm depth) collected at three locations in the Limfjord, Denmark, were investigated. Eelgrass plants were divided into roots, rhizomes, stems and leaves according to age, and the metal content in each fraction was determined. The distribution pattern of the metals could be divided into separate groups according to the following criteria: 1. (i) the age-dependent distribution pattern of the metals in the leaves (the concentrations of Ca, Cd, Fe, Mg, Mn, Na, Pb and Zn increased with the age of the leaves; the concentrations of Cu and K decreased with age); 2. (ii) the concentration level of the metals in the roots compared to that in the rhizomes (Ca, Cd, Cu, Fe, Mn, Pb and Zn concentrations were highest in the roots; K, Mg and Na concentrations were highest in rhizomes); 3. (iii) the concentration level of the metals in the ‘stem’-fraction compared to that in the youngest leaf (the concentration of Fe, K, Mg, Na and Pb were highest in the ‘stem’-fraction; the concentrations of Ca, Cd, Mn and Zn were highest in the youngest leaf). The distribution pattern of the metals are discussed, especially in relation to the gross morphology of eelgrass. Finally, the relatively large quantity of metals tied up in the eelgrass biomass at the three localities indicated that the eelgrass beds most likely exerted a significant role in the metal cycling in the Limfjord.