Many attentions have been paid to the decrease of reef-building corals, which are main composers in coral reef ecosystem, by environmental changes at global and local scales. It is an urgent issue to evaluate how corals cope with future environmental changes. There are many laboratory experiments which have evaluated the coral responses to environmental changes by focusing on some parameters (e.g., growth rate, mortality, photo synthetic activity), and several reviews have been also published. However, the review focusing on how corals could acclimatize to several levels of environmental changes is limited. In addition, the possibility whether corals could adapt to environmental changes through the change of genetic composition within a population has been rarely focused. In this review, we summarize basic knowledge on the acclimatization mechanism of corals to environmental changes (temperature, ocean acidity, nutrient, light intensity, etc), the possibility of adaptation, and discuss future direction of this research area.

Elevated CO₂ caused by human activities is thought as a cause of future climate change driving global warming and ocean acidification. In order to predict global environments in the near future, it is required to understand the past environmental change and its process in detail. While it is well known that biogenic carbonates such as foraminifera and coccolithophorid are attractive tools to reconstruct the past environments, scleractinian corals also provide environmental data around tropical to subtropical region with much higher time resolution. In this review, I summarize previous works on paleo-environments based on chemical components of fossil and modern coral skeletons in order of the age from Pliocene to the present. Then recent studies concerning elemental variability in micro scales of skeletal surfaces and current issues accompanying with new findings from these studies are discussed. I hope that this review will inspire further study in this field.

Calcification mechanism of reef-building corals and its response to global environmental changes are reviewed based on the recently published literature. Coral calcification is an extracellular reaction occurred in subcalicoblastic extracellular calcifying medium. To maintain progress of calcification, calcium ions and dissolved inorganic carbon species are needed to be supplied in the calcifying medium while calcification inhibitors such as protons should be removed efficiently. Catalytic reaction of carbonic anhydrase in calicoblastic endoderm layers seems to play important role for fast calcification of corals. Better understanding on coral calcification is essential to evaluate on-going ocean acidification impact on reef calcification. More integrated research strategy is required including physiology, skeletal geochemistry, and molecular biology.