How warming conditions reshape crown-of-thorns starfish threats to coral reefs
Researchers from the University of Sydney have highlighted a surprising dynamic in the battle to protect corals from climate change. They identify that the young crown-of-thorns starfish pose a significant risk to coral populations, potentially surpassing some traditional stressors that have long troubled reef ecosystems. The findings appear in the journal Global Change Biology, signaling a shift in understanding how warming oceans interact with reef predators.
The crown-of-thorns starfish, commonly called COTS, is a major predator of corals. In the Indo-Pacific, including the Great Barrier Reef, these starfish can devastate extensive coral cover. While storms and elevated sea temperatures remain direct drivers of coral decline, COTS outbreaks contribute substantial additional damage. The recent work underscores that COTS threats are continuing to be driven by their own biology and environmental conditions, rather than by a single external factor alone.
In the experiments, researchers observed that younger COTS individuals show a notable resilience to higher temperatures. They tolerate heat levels that would stress or harm adult starfish, a finding that implies the potential for more enduring and widespread predation on vulnerable coral colonies as oceans warm. With ongoing climate change, this heat tolerance could translate into longer-lasting outbreaks and greater cumulative harm to reef systems.
Lead investigator Professor Maria Byrne explained that temperature measurements over time demonstrated how much heat young COTS can withstand. The study indicates that these juveniles can endure nearly three times the heat intensity that typically triggers coral bleaching. This resilience shifts the balance of risk toward reefs, as the juvenile starfish can survive conditions that would suppress or slow other reef organisms, allowing predation pressure to persist even under warming scenarios.
Experts note that the rapid spread of crown-of-thorns outbreaks is not only a biological issue but also an ecosystem and human-environment concern. The reduction of natural enemies due to overfishing removes a critical control on COTS populations. Additionally, nutrient enrichment from land runoff can boost algae growth, indirectly supporting larger COTS numbers by altering coral health and the surrounding ecological balance. Together, these factors accelerate the spread and impact of this starfish on coral communities across the Indo-Pacific region.
Beyond predation, researchers point to complex interactions among reef species and environmental stressors. Coral reefs rely on a delicate equilibrium, where disease, predators, and climate factors interact in ways that can either bolster resilience or hasten decline. The study’s findings emphasize the need for integrated reef management that considers predator control, water quality, and climate adaptation strategies to safeguard coral ecosystems for the future.
Historically, scientists have also explored the idea of disease-resistant corals as a potential buffering mechanism. While the notion of resilient corals offers hope in some contexts, the current work centers on the immediate threat posed by COTS and how temperature dynamics intersect with predation pressure. The overarching message is clear: protecting reefs requires addressing warming oceans, nutrient runoff, and the ecological balance that governs predator-prey relationships on these critical marine habitats.