Changes in abundance and size-structure of Pocillopora spp. in Lian, Batangas

• Main Author: Calansingin, Marc John C.
• Format: text
• Language: English
• Published: Animo Repository 2012
• Subjects: Biology
• Online Access: https://animorepository.dlsu.edu.ph/etd_bachelors/2467
• Institution: De La Salle University

Many of the world reefs are under threat from disturbances such as coral bleaching and outbreaks of Acanthaster planci. In this study, the effects of these disturbances to the abundance and size-structure of Pocillopora in Lian, Batangas are evaluated. Pocillopora colonies in Lian, Batangas in May 2010, October 2010, and April 2011 were counted and measured. In addition, occurrence of partial bleaching, partial mortality, and melanic response among the colonies were also recorded. Measured Pocillopora colonies were then assigned to size classes to evaluate changes in size distribution over time. Results show that in May 2010, there were generally fewer large colonies compared to smaller colonies. Furthermore, these large colonies exhibited greater occurrence of partial mortality relative to smaller colonies. From this it was hypothesized that an undocumented outbreak of A. planci occurred prior to May 2010, and these corallivores selectively fed on large colonies more than on the smaller ones. In addition, results also show a general decrease in abundance and shrinkage of Pocillopora in Lian from May 2010 to April 2011. This coincides with the observed bleaching episode in Lian that started in May 2010, peaked in October 2010, and finally subsided in April 2011. During this event, larger colonies of Pocillopora experienced greater susceptibility to coral bleaching, as reflected by the greater occurrence of partial bleaching and partial mortality among these large corals. Occurrence of a melanic response, hypothesized to be a form of resistance to bleaching, is also seen greatest in large colonies. Using a matrix projection model to simulate the effects of the observed bleaching event, it was confirmed that the observed shrinkage in size-structure of Pocillopora in Lian is most possibly due to the bleaching event. In addition, simulations of the bleaching episode returning every 10 years project that only 10% of the population would survive after 50 years. More so, if bleaching occurs every 5 years, Pocil