Metal Content on the Reef Coral Porites astreoides: an Evaluation of River Influence and 35 Years of Chronology

Ten metals (Al, Ca, Cd, Cu, Cr, Fe, Hg, Pb, V and Zn) were analysed in skeletal sections of the coral Porites astreoides. Each skeletal section comprised five years of growth, and a total of 35 years of carbonate deposition was analysed from 1960 to 1995. The skeletal sections were determined through the analysis of growth bands using tomography. The corals were taken from two localities that differ in their sedimentation rate and closeness to river inputs that were considered as factors that could lead to differences in coral metal content. The concentration of most metals did not differ throughout the period of time analysed. This, together with the fact that most metals showed concentrations higher than others reported for pristine locations in the Caribbean, suggests a relatively chronic contamination of the study site established at least since 1960 for the metals analysed. Only the skeletal content of Al, Fe, Cr and Ca differed significantly between localities: (a) corals from the locality closer to the river inputs had a greater concentration of Al and Fe; (b) the difference in Cr was only due to an increased concentration in one colony, although detectable in 3 skeletal sections (15 years), and; (c) the skeletal Ca difference could be associated with different growth rates between localities.