METAMORPHOSIS OF HETEROXENIA-FUSCESCENS-PLANULAE (CNIDARIA, OCTOCORALLIA) IS INHIBITED BY CRUDE-OIL - NOVEL SHORT-TERM TOXICITY BIOASSAY

By using TPA (12-tetra-decanoyl-phorbol-13-acetate) an artificial indu cer for metamorphosis, it was possible to determine the effect of crud e oil on settlement and metamorphosis of planulae of the soft coral He teroxenia fuscescens. In the absence of crude oil, TPA induced metamor phosis in 97% of these planulae. The effect of crude oil on metamorpho sis and appearance of deformed primary polyps was concentration depend ent. Only 50% of the planulae grown in experimental vessels with crude oil at a concentration of 0.1 ppm covering the bottom and walls of th e vessels underwent metamorphosis when triggered by TPA. Of those plan ulae exposed to 100 ppm of the pollutant only 3% metamorphosed after b eing induced by TPA. Furthermore, oil film on the water surface was le ss toxic to the larvae than the crude oil covering the bottom and wall s of the experimental vessels. Some of the oil treated planulae died, while others remained viable, looked normal, but did not metamorphose after being presented with TPA. These findings suggest that even at ve ry low concentrations crude oil affects larvae of H. fuscescens preven ting their settlement and metamorphosis. Therefore it is possible that oil spills affect coral recruitment by decreasing the viability and t he settlement of coral planulae. This assay represents a new sensitive bioindicator to detect the impact of oil pollution on tropical and su btropical marine environments. Copyright (C) 1996 Elsevier Science Ltd .