Dynamics of Crown-of-Thorns Starfish and Coral Reef Health

The crown-of-thorns starfish (COTS, Acanthaster spp.) is one of the principal biotic agents driving coral decline across the Indo-Pacific. Characterised by episodic ‘outbreaks’, dense aggregations of COTS can decimate reef-building corals, undermining the structural complexity and biodiversity of reef ecosystems. Outbreak dynamics are shaped by a suite of interacting factors including larval nutrition, ocean warming, acidification and overfishing of natural predators. Elevated nutrient inputs can boost phytoplankton blooms, enhancing larval survival and fuelling population growth. Concurrently, rising sea temperatures and fluctuating pH regimes influence larval development and stress tolerance, often conferring resilience to COTS relative to their coral prey. The temporal and spatial patterns of outbreaks also reflect hydrodynamic dispersal of larvae, local reef condition and the efficacy of management interventions. Manual removal, zoning of marine protected areas and improvements in water quality have all been trialled to mitigate outbreaks, with manual control typically yielding the most immediate benefits at the site level. A nuanced understanding of COTS life history, combined with targeted management and reef resilience strategies, is essential to safeguard coral cover and the myriad ecosystem services provided by healthy reefs.

Research from Nature Portfolio

Recent studies have shown that the interactive effects of food availability, warming and acidification critically determine larval performance. Under projected temperature and pH scenarios, starfish larvae fed a high phytoplankton ration exhibited accelerated development and reduced abnormalities, whereas low or variable rations constrained growth despite warming. Investigation of management approaches revealed that repeated manual removal of COTS at outbreak sites consistently reduces densities and facilitates coral recovery, whereas marine protected area zoning and current water-quality programmes deliver only marginal benefits. Foundational work has also demonstrated that modest increases in sea temperature can amplify larval development rates under nutrient-rich conditions, indicating that climate warming acts as a potent co-driver of outbreak initiation.

Dynamics of Crown-of-Thorns Starfish and Coral Reef Health publication trend

The graph below shows the total number of articles in dynamics of crown-of-thorns starfish and coral reef health across all publications each year (not limited to Nature Index journals).

Technical terms

Crown-of-thorns starfish (COTS): A coral-predating sea star (genus Acanthaster) responsible for episodic outbreaks that can devastate reef ecosystems.

Coral bleaching: The loss of symbiotic algae from coral tissues, typically induced by thermal stress, leading to whitening and potential mortality.

Ocean acidification: The reduction in seawater pH due to increased atmospheric CO₂ uptake, affecting calcification and development in marine organisms.

Phytoplankton: Microscopic photosynthetic organisms that form the base of marine food webs and serve as a key larval food source for COTS.

Manual removal: A targeted management intervention involving the physical extraction or injection of control agents into COTS individuals to reduce densities.

Transcriptomics: The study of the complete set of RNA transcripts produced by an organism, used to elucidate gene expression patterns across conditions or seasons.

References

1. Juvenile waiting stage crown‐of‐thorns sea stars are resilient in heatwave conditions that bleach and kill corals. Global Change Biology (2023).
2. Crown-of-thorns seastar (Acanthaster spp.) feeding ecology across species and regions. The Science of The Total Environment (2024).
3. Seasonal tissue-specific gene expression in wild crown-of-thorns starfish reveals reproductive and stress-related transcriptional systems. PLOS Biology (2024).
4. Variable food alters responses of larval crown-of-thorns starfish to ocean warming but not acidification. Communications Biology (2023).
5. Thirty Years of Research on Crown-of-Thorns Starfish (1986–2016): Scientific Advances and Emerging Opportunities. Diversity (2017).
6. Known Predators of Crown-of-Thorns Starfish (Acanthaster spp.) and Their Role in Mitigating, If Not Preventing, Population Outbreaks. Diversity (2017).
7. Potential Enhanced Survivorship of Crown of Thorns Starfish Larvae due to Near-Annual Nutrient Enrichment during Secondary Outbreaks on the Central Mid-Shelf of the Great Barrier Reef, Australia. Diversity (2017).
8. Climate change as an unexpected co-factor promoting coral eating seastar (Acanthaster planci) outbreaks. Scientific Reports (2015).
9. Outbreak of coral-eating Crown-of-Thorns creates continuous cloud of larvae over 320 km of the Great Barrier Reef. Scientific Reports (2015).
10. Assessing Different Causes of Crown-of-Thorns Starfish Outbreaks and Appropriate Responses for Management on the Great Barrier Reef. PLOS ONE (2016).
11. Impacts of Ocean Acidification on Early Life-History Stages and Settlement of the Coral-Eating Sea StarAcanthaster planci. PLOS ONE (2013).