Title: Experimental investigation of UV tolerance in hermatypic corals (Scleractinia)
Abstract: Effects of artificial radiation on various species of coral from the Great Barrier Reef were studied.The corals were either exposed to artificial white light during and after UV-treatment or were kept In darkness subsequent to UV exposure.When not exposed to white light, the UV tolerance of corals taken from depths of up to 1.5 m was, on average, double that of those collected at 18 to 20 m.Under the ~nfluence of short wavelength visible light (max.effectiveness 450 to 500 n m ) , UV tolerance increased on average by a factor of 6.It is postulated that protection from UV light involves at least 2 different physiolog~cal mechanisms: screening by UV-absorbing compounds and recovery due to photoreact~vation.The most conspicuous symptom of serious radiation damage to polyps was extrusion of mesenterial filaments through the mouth opening and entire body surface Slmllar but less pronounced reactions could b e induced in non-irradiated polyps by exposing then1 to rad~ation-damaged polyps, In particular when the unexposed polyps were a different species.Such interactions never occurred, however, between polyps from the same colony.It is therefore conjectured that there is a specific protective mechanism that impedes the spread of secondary damage from damaged polyps to others in the same colony