7. Effect of lower pH on settlement and development of coral, Pocillopora damicornis (Linnaeus, 1758)

Voranop Viyakarn (1), Wipada Lalitpattarakit (1), Narainrit Chinfak (1), Suppakarn Jandang (1), Pataporn Kuanui (1), Somkiat Khokiattiwong (2), Suchana Chavanich (1)*

1 Reef Biology Research Group, Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
2 Phuket Marine Biological Center, Department of Marine and Coastal Resources, Phuket 83000, Thailand

The effects of pH reduction on the settlement and development of the coral Pocillopora damicornis were investigated. Three different pH treatments (pH = 7.6, 7.9, and 8.1) were used. In addition, water quality (temperature, salinity, total alkalinity) around the study site was monitored. The results showed significant differences in the settlement rates of Pocillopora damicornis larvae between pH treatments (p < 0.05). A decrease in pH levels caused a strong decline in larval settlement rate. In addition, at pH 7.6 and 7.9, all larvae were unable to complete metamorphosis, and metamorphosis delay was observed. Field monitoring showed low fluctuation of all seawater parameters within 24 hours, and there was no difference between seasons. From this study, a strong negative effect of pH reduction on P. damicornis larvae was observed. Although the function of physiology is still not clearly understood, correlations are likely to exist.