The major threat to one third of the world’s reef-building corals is global climate change (8), with temperature extremes leading to coral bleaching. During bleaching, the symbiotic algae are expelled, resulting in weak and vulnerable corals that are susceptible to disease. Climate change may also increase the severity of El Niño events and storms with strong waves and currents which destroy coral reefs. Greater levels of carbon dioxide in the atmosphere also cause increased ocean acidification, which can reduce a coral’s ability to create its hard skeleton. In addition, rising sea levels may cause less sun to reach the coral, thereby decreasing photosynthesis (1).
Localised threats to Ctenella chagius include human development, such as industry, settlements, and agricultural and industrial pollution. Sediment which runs into the sea from soil erosion disrupts photosynthesis, and tourism and its related activities release pollutants into the water, whilst invasive species can disrupt the natural balance of the reef. Also, several methods of fishing, including dynamite, chemical and bottom trawling, can damage coral (1).