Coral bleaching is primarily caused by environmental stress, most notably elevated sea temperatures. However, biological factors can also contribute. Outbreaks of predatory starfish, specifically the Crown-of-Thorns starfish (Acanthaster planci), are known to cause significant damage to coral reefs by feeding on polyps. Severe predation can weaken the coral, making it more susceptible to bleaching, or cause direct mortality that appears as whitening (tissue loss revealing the white skeleton). Keppel Island, being part of the Great Barrier Reef ecosystem which experiences COTS outbreaks, is susceptible to such damage. While climate change and rising temperatures are the main driver of widespread bleaching events, localised stress from predators like starfish can exacerbate or cause bleaching in specific areas. Given the options, Starfish (Crown-of-Thorns) is the only organism listed that is a known significant predator of coral and contributes to coral damage and bleaching.