The viability of marine macrophytes being used as monitors of heavy metal contamination in coastal zones was evaluated by analysis of the concentration of certain elements in two brown algae species, Padina gymnospora and Sargassum stenophyllum, and in a seagrass species, Halodule wrightii. These species were collected in two Rio de Janeiro State regions, Sepetiba Bay, which has been the brunt of an environmental degradation process over the last decades, and Ribeira Bay, a non-contaminated area. In addition, in situ transplant experiments with P. gymnospora between the two regions were done. The two algal species presented a similar behavior regarding heavy metal accumulation, indicating high concentrations of Zn and Cd in Sepetiba Bay in relation to Ribeira Bay, a wide distribution of these metals along Sepetiba Bay, and a non seasonal temporal variation of heavy metal levels, this being related to the inputs of the metal throughout into the Bay. The results of transplant experiments show that P. gymnospora is able to accumulate the studied metals in a short period of time (one month) thus reflecting the ambient bioavailability in Sepetiba Bay, and a low plant metal release in the non-contaminated region. In relation to the seagrass H. wrightii roots and leaves were the main compartments to metal accumulation and the high metal concentration in the roots found in Sepetiba Bay populations could reflect the metal bioavailability in sediments.
heavy metals; coastal ecosystems; Padina gymnospora; Sargassum stenophyllum; Halodule wrightii