Download EMPHASIS ON REPRODUCTION AND EARLY LIFE STAGES

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.
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