Senona A. Cesar, Homer Hermes Y. De Dios, Naomi B. Amoin, Danilo T. Dy
Corals lose their pigments or cell symbionts with prolonged exposure to temperatures higher by 1°C than the reef ambient temperature, leading to bleaching. Heliofungia actiniformis, a top traded coral was subjected to lower (24-26°C), ambient (27-29°C), and higher (30-32°C) thermal conditions to determine the resilience of its zooxanthellae to thermal stress. The experiment followed a complete randomized design with three different temperatures and eight replicates per treatment level. Evaluations were done in terms of density of expelled zooxanthellae, biomass of expelled chlorophyll-a, and using a coral color reference card. Thermal stress had a significant effect on the density (F 2,21 =3.691; p=0.042) and chlorophyll-a biomass (F 2,21 =10.711; p=0.001) of expelled zooxanthellae of H. actiniformis. Density and chlorophyll-a biomass of expelled zooxanthellae in the 30-32°C treatment doubled and tripled, respectively, compared to ambient conditions. However, these were still lower compared to published values for branching corals. The capability of H. actiniformis for downward migration to seek refuge, and its thick gastrodermis that harbors the zooxanthellae are possible adaptive mechanisms to survive the changing thermal conditions of tropical reefs. © 2014, Science and Technology Information Institute. All rights reserved.
Visayas State University Visca, Baybay City, Leyte, Philippines; Southern Leyte State University, Bontoc, Southern Leyte, Philippines; University of San Carlos, Cebu City, Philippines
