Metal levels in estuarine macrophytes: Differences among species

With the aim of studying the interspecific differences in the bioaccumulation of a series of elements in six species of estuarine macrophytes, we measured the concentrations of various metals (Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), as well as C and N, in several species of macroalgae and one species of seagrass in estuaries in northwest Spain. To facilitate the interpretation of the results, we also determined the concentrations of the same metals in sediments. Contamination by particulate metal did not appear to be important. The levels of Cu in the different species were generally high in comparison with those found in similar studies; in contrast, the concentrations of Ph and Zn were relatively low. The metal concentrations showed greater variability and a distribution that was further from normal than those of C and N. In general the highest concentrations of elements were found in Enteromorpha spp. and Zostera nolti, and the lowest occurred in Ulva spp. There were several significant positive correlations among tissue concentrations of Cr, Cu, and Ni. There were also significant correlations between tissue concentrations of N and Zn, suggesting possible synergetic effects between them. Cluster analysis dearly revealed that the chemical composition of Z. noltii differed from that of the macroalgae. Macroalgae were not grouped according to their taxonomic position, therefore it appears that the concentrations of the elements depended more on the ecological traits of the macroalgal species rather than on any possible physiological differences among different taxonomic groups. Of the species studied, Ascophyllum nodosum and Enteromorpha spp. appeared to be the best biomonitors of metal contamination.