Zoological Studies

Effects of Acidified Seawater on the Skeletal Structure of a Scleractinian Coral from Evidence Identified by SEM

Isani Chan, Shao-Hung Peng, Ching-Fong Chang, Jia-Jang Hung, and Jiang-Shiou Hwang (2012) This study investigated the response of the scleractinian coral Acropora valida to acidified seawater from the Kueishan I. hydrothermal fields off northeastern Taiwan.  Acropora valida was exposed to seawater with various pH values, and modification of the skeletal structure was examined and recorded through scanning electron microscopy (SEM).  The SEM images displayed various degrees of erosion of the vertical rods and radial bars, and considerable and significant acidified seawater effects on the fusiform crystals and small spherulitic tuft clusters of aragonite as the pH decreased in the experimental treatments.  The results demonstrated that a low pH may inhibit coral calcium carbonate formation, implying that the pH may be the limiting factor in the coral's distribution around the Kueishan I. hydrothermal fields.  Morphological changes in scleractinian coral skeletal structures with erosion of CaCO₃ crystals could also be explained by the saturation state (Ω) of the experimental seawater with respect to aragonite under various pH conditions.  Because ocean acidification is an urgent global environmental issue, the implication is that Kueishan I. hydrothermal vents have a considerable influence on the spatial distribution of corals around Kueishan I. This was demonstrated by the use of coral, A. valida, as a model species in the present study.