Effects of Oil Pollution on Coral Reef Communities

This paper reviews our knowledge of 011-pollution effects on coral-reef communities, concentrating on research done since the last review on this subject by Johannes (1975). The review focusses on crude-oil effects on scleractinian corals and octocorals and summarizes the small amount of work conducted on other reef organisms, as well as on the reef flora. Until 1975 there appeared to be no conclusive evidence that oil floating above the reef damages the corals. Although conflicting reports continue to appear in the literature, growing evidence indicates a detrimental influence of oil pollution on coral-reef communities. Laboratory experiments and long-term field studies in the Red Sea witness detrimental effects of oil pollution on reef corals, such as complete lack of colonization by hermatypic corals in reef areas chronically polluted by oil, decrease in colony viability, damage to the reproductive system of corals (smaller number of breeding colonies, decrease in number of ovaria per polyp, fewer planulae per coral head and premature planulae shedding), lower life expectancy of planulae and abnormal behavioural responses of planulae and corals. Other detrimental effects on reef corals caused by crude oil, mainly reported from the Caribbean, include lower growth rates, direct damage to tissues, thinning of cell layers and disruption of cell structure. damage to tactile stimuli and normal feeding mechanisms, excessive mucus secretion leading to enhanced bacterial growth and eventual coral destruction. All investigators studying effects of crude-oil emulcifiers on reef areas polluted by oil conclude that these enhance the damage; hence mechanical oil removal is recommended. There IS urgent need for more field and laboratory research on long-term oil-pollution effects on coral-reef communities. Suggestions are made as to the type of studies required for a better understanding of the problem.