Crown of Thorns Removal at Kayankerni Marine Sanctuary
The crown-of-thorns (COTs) starfish is a predator that feeds on corals and can consume up to 12m² of coral tissue per year. While COTs are a natural part of reef ecosystems, their infestation (densities greater than 30 starfish per hectare) can be detrimental to reef health. Regulating such outbreaks can be even considered as a form of reef restoration.
Eradication of COTs from reefs is mainly practiced either through targeted culling or toxic chemical injection into the starfish body. Eradication measures should be carried out with proper safety protocols in place, as their tissues contain venom that can cause sharp stinging pain lasting several hours, persistent bleeding, nausea, and tissue swelling.
Due to the long-term coral reef monitoring carried out by Blue Resources Trust (BRT), such an outbreak was detected at the Kayankerni Marine Sanctuary in July 2025. Based on scientific and data-driven observations, and in consultation with experts, COT removal was carried out through targeted culling at this site. Additionally BRT was also supported by the local community, who understood the value of preserving their natural reef resources.
Divers extracted the COTs while ensuring minimal harm to the corals. Over two days of extensive removal, 107 COTs were extracted, transported to shore, and buried to avoid risk to land animals and humans. Observations clearly showed that this effort was effective, as evidenced by the decrease in the starfish density as well as the reduced COTs-related bleaching and mortality on the reef.
Water quality monitoring conducted by BRT in July and August, demonstrated a sudden increase in chlorophyll-a, suggesting that COT infestation is potentially triggered by high nutrient levels. This further emphasises the importance of continuous monitoring of all oceanographic and ecological parameters related to the ecosystem, especially where human interaction is high, to ensure sustainability of coral reefs.