Possible Index for Marine Pollution from Scleractinean Corals in Northern Gulf of Aqaba, Jordan

Abstract

The coral nubbins of Stylophora sp., Pocillopora sp., Acropora sp., Fungia sp., and Porites sp. were taken from shallow depths of about 5 m by SCUBS diving. Another set of coral samples were collected in front of the Marine Science Station for incubation experiments to study the resistance of corals to different concentrations of heavy metals ranged between 0.1 to 50 ppm. The skeleton and tissue layers of all coral samples were isolated for samples, digested (using a mixture of Nitric and Hydrochloric acids) and were analyzed to determine the concentrations of Cd, Cu, Pb, Cr, Zn, and Ni using Flame Atomic Absorption Spectroscopy (FAAS). However, the lowest concentrations were found along the marine park including the Marine Science Station, with lower contamination of ambient waters as heavy metals concentration in corals reflects the health of marine environment. The highest concentrations of all heavy metals (Cd, Cu, Pb, Zn, Cr, and Ni) in the coral skeletons were accumulated in Pocillopora species whereas the lowest concentrations were recorded in Porites species and the rest coral species could be arranged in the following ranking order (from high to low concentrations): Pocillopora sp.> Acropora sp.> Stylophora sp.> Fungia sp.> Porites sp. The incubation experiment showed that the toxicity of the individual metals increased in all coral species with increasing metal doze and time of exposure until total death was reached. The coral species resistance to death for all heavy metals (except for Nickel) can be arranged in the following ranking order (from low to high): Stylophora sp.< Acropora sp.< Pocillopora sp.< Fungia sp.< Porites sp. The coral species Porities was the most resistant species. Copper was found as the most toxic metal to all coral species compared with the toxicity of Pb, Cd or Zn. The toxicity of the studied heavy metals (except Ni) to all corals species can be arranged in the following order (from high to low): Cu>Pb>Cd>Zn. It is generally concluded that the pollutions levels of heavy metals along the Jordanian coast of the Gulf of Aqaba are still relatively low and the coral reef communities are healthy. Corals are suitable to be used as proxy tools to record environmental pollution (bio-indicators) from the Gulf of Aqaba and the Red Sea.

Keywords: Heavy metals, Corals, Gulf of Aqaba, Red Sea.