Abstract

Coral reefs are of great importance in Iraqi marine environments but are potentially threatened by human activities. According to this study, the heavy metals in the hard skeletal elements of Octocoral Menella and Platygyra pini Chevalier coral reef species were measured at two stations, P-1 and P-2, respectively. In order to understand the pattern of distribution of heavy metals in these reefs, the analyses of Sr/Ca ratio, physico-chemical parameters of seawater, and heavy metal concentrations in ambient seawater were conducted. It was found that the accumulation of heavy metals in coral reefs varied according to species. In Octocoral Menella species, the distribution of heavy metals follows the pattern: Fe>Ti> Mn> Cr> Zn> Cu> Ni> Pb, while in Platygyra pini Chevalier the pattern is Fe> Ti> Zn> Mn> Cr> Cu> Ni> Pb. The physico-chemical parameters of seawater at P-2 station represented by pH, EC, TDS, Na+, K+, Ca2+, Mg2+, Cl-, and CO32- are more than P-1. Concentrations of Fe, Cr, Mn, Ni, and Ti were generally higher in Octocoral Menella than Platygyra pini Chevalier. The Sr/Ca ratio in Platygyra pini Chevalier is higher than the Sr/Ca ratio in Octocoral Menella, which suggests that Platygyra pini is formed under relatively highly saline water conditions. Concentrations of Fe, Cr, and Ni in seawater were higher at P-1 than at P-2, while Cu, Zn, and Pb were higher at P-2. The accumulation of heavy metals in coral reefs mainly depends on the heavy metal content in surrounding seawater. The increase in seawater salinity and electrical conductivity is compatible with the increase in the Sr/Ca ratio and in the concentrations of Cu, Pb, and Zn in Platygyra pini Chevalier and sea water at P-2 station. In terms of how these results compare with heavy metal accumulations recorded in previous studies of coral reefs at other locations in the Arabian Gulf and around the world, the accumulation of Fe was higher than previous studies, suggesting the extensive contamination of coral reefs in the Iraqi marine environment. The present study represents the start of an environmental monitoring process to determine appropriate input limits of heavy metals in coral reefs in this region in order to protect this important aspect of the marine ecosystem.