ABSTRACT STR ESS B I O L O G Y IN P H I L I P P I N E P O C I L L O P O R I D >: E M P H A S I S ON R E P R O D U C T I O N AND EARLY L I F E S T A G E S Ronald D. Villanueva University of the Philippines, 2006 Adviser: Dr. Marco Nemesio E. Montano The health of coral reefs is increasingly threatened by anthropogenic stressors. The stress responses of the several brooding pocilloporid corals in Bolinao, northwestern Philippines to fish farm effluent and natural gas condensate - water-accommodated fraction (WAF) were investigated. Stress responses pertaining to life-sustaining aspects in the biology of these corals, e.g., reproduction and early life stages were given emphasis; hence a feature of their reproduction, i.e., the timing of larval release, was also investigated. The coral Pocillopora ciamiconns incurred diminishing larval output, growth (nubbin), and survivorship (mature colony, nubbin and spat) after exposure to environments of increasing concentration o f f i s h farm effluent. In the fish farm environment, no spat of the coral Seriatopora caliendrutn survived. Furthermore, metamorphosis ol P. ciamicornis larvae was limited in substrates from the fish farm environment. These effects may be due to various physico-chemical modifications of the marine environment (including enhanced sedimentation and eutrophication) emanating from the massive organic matter discharge in intensive fish farming. With such detrimental effects to different aspects of coral biology, especially reproduction and early life stages, the development and sustainability of a coral community is not possible in the affected areas. Limited effect of condensate W A F to reproductive output of Pocillopora ciamicornis was observed from exposure during gametogenesis. Whereas, abortion of brooded larvae occurred during embryogenesis, with those aborted during the early embryogenic phase exhibiting smaller sizes, lower metamorphic competency, and white color (indicative of low symbiont density) compared to those aborted during late embryogenesis, hence recruitment success can potentially be reduced. Moreover, variable toxic responses (in terms of lethality, metamorphic competency, and subsequent juvenile growth) of the larvae of five pocilloporid coral species were observed upon exposure to condensate WAF. The sensitivity ranking of these species to such oil stress is: Seriatopora guttatm > S. hystrix > Stylophora pistillata > Pocillopora verrucosa > P. damicornis. This differential susceptibility can potentially explain the relative abundance and pattern of distribution of these corals in oil-contaminated sites. 1 he six pocilloporid corals investigated exhibit remarkable seasonal and lunar periodicity in their larval production. High larval outputs in these corals generally occur during the warm-dry season, though they also planulate during the wet and cooi seasons. The peak of larval release in four species (P. damicornis, P. verrucosa, S. pistillata and S. guttatus) happens between first quarter and full moons, during last quarter moon for S. hystrix. and new moon for S. caliendrum. The timing of larval production can help explain temporal recruitment patterns of the species. Altogether, the responses of these corals to stress and their reproductive timing can have profound consequences on their pattern of distribution and abundance in space and time. VI