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

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 com-positions, namely net pen fish farming with annual fish production of 2.4 × 10 6 kg yr −1 . 5 We sampled and studied long coral cores from stressed, remote and intermediate lo-calities 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 maricul-ture 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 ge-10 ographical gradient and depended on proximity to the source of contamination. We suggest that δ 13 C of coral skeleton is a promising proxy for identifying long term pro-cesses of coral growth under high nutrient loads and potential disturbances to the coral reef ecology.