Abortion Effect in Corals Induced by Oil Pollution

Abstract

Sublethal concentrations of Iranian crude oil induce immediate mouth-opening in the Red Sea coral Stylophora pistillata, followed by premature extrusion of planulae larvae. Laboratory experiments with different concentrations of water soluble fractions (WSF) of Iranian crude oil (0.1-10.0 ml-l), showed that the average number of planulae extruded in each oil concentration was significantly higher than in the control. In natural conditions S. pistlllata sheds its planulae only during the night. In presence of WSF of crude oil, shedding is immediate, day or night. Shedding of planulae during an oil spill decreases their viability and chances of successful settlement. In chronically oil-polluted reefs, such as the coral nature reserve of Eilat, almost no colonization of new coral colonies occurs, while high colonization is evident in reef areas free of oil pollution.