Anthropogenic stressors and eutrophication processes as recorded by stable isotopes compositions in coral skeletons

Abstract. The northern Gulf of Aqaba, in the northeastern branch of the Red Sea, is a clear example of humans effecting on the health of fringing reefs. Our results demonstrate the effect of an anthropogenic stressor on the carbon and oxygen stable isotopes compositions, namely net pen fish farming with annual fish production of 2.4×10⁶ kg yr⁻¹. We sampled and studied long coral cores from stressed, remote and intermediate localities and short- term transplanted Porites sp. colonies from the west side of the Gulf of Aqaba to a remote and a polluted sites, respectively. The data shows that mariculture and other human related stressors did not influence the oxygen isotopic signature over a period of two decades. However, the carbon fractionation changed along a geographical gradient and depended on proximity to the source of contamination. We suggest that δ¹³C of coral skeleton is a promising proxy for identifying long term processes of coral growth under high nutrient loads and potential disturbances to the coral reef ecology.