Using coral skeletons for monitoring of heavy metals pollution in the Red Sea Coast, Egypt

The present work is the first study to specifically highlight a correlation between two different methods to monitor environmental pollution using hard corals as biomonitors. The first method involved comparing the concentrations of heavy metals in modern coral skeletons in both coasts of the Hurghada and Ras Mohamed nature reserve sites, whereas the second method involved comparing these concentrations in living coral species and the same Pleistocene ones. The results showed a similarity between the two monitoring methods. These results showed that the modern corals on the Hurghada site were enriched in all heavy metals in comparison with Ras Mohamed especially for Cu, Zn, Ni, and Co. The concentrations of these metals were higher than those in coasts of Red Sea (Saudi Arabia), Gulf of Aqaba (Jordan), Gulf of Mannar (India), Panama, Central America, and Australia. Furthermore, Hurghada coral skeletons suffered from higher concentrations of Cu, Pb, Cd, and Co than those in the earth's carbonate rocks. These elements may enter Hurghada's marine ecosystem by anthropogenic impacts as contamination from antifouling paint and oil spill from vessels. On the other hand, the Ras Mohamed site seems to be relatively unpolluted, except by Pb presumed to be due to oil spills from boat engines involved in extensive diving activities. The present work suggests that some coral species can be used as pollution biomonitoring as Stylophora pistillata for Cu and Co, Fungia scutaria for Zn and Cd, Pocillopora verrucosa for Pb, and Porites solida for Fe, Cu, and Ni. The microstructure and microarchitecture of the studied species play the essential role in the pollutant uptake, where the large reactive surface area and the amounts of intercrystalline porosity in coral skeletons are directly proportional to their amount of metal content. In spite of the mentioned results, the growth abnormality is not distinguished for the polluted recent species.