Threats to coral reefs
Marine pollution
Oil spills are only one of the many sources of marine pollution. Once corals are oil polluted, they may show several effects (acute as well as chronic) such as a reduced level of reproduction, for exampple. Oil pollution can also hinder the proces of photosynthesis of the algae (zooxanthellae) by blocking the sunlight.
More detailed information about marine pollution is available in the marine pollution tutorial.