Skip to main content

Crown of Thorn Presentation by Emma Cachione



Emma Conchione - A Sunshine Divemaster in training, who also has been studying through New Heaven with their Ecological Internship Programs, recently conducted a briefing on Crown of Thorns and how we can help balance the ecosystems on Koh Tao at various dive sites through removal of these spiny marine life creatures.

Image removed.
"Emma presenting the Crown of Thorns information to Divemasters, Staff and Guests"

What is the Crown of Thorns?  It is an invertebrate : Group of Echinoderm Phylum same as Spiky Skin.

  • Long Spiny Black Sea Urchin
  • Marbled Sea Cucumber
  • Black Sea Cucumber
  • Pinkfish Sea Cucumber
  • Orange Spiked Sea Cucumber

Some of the common characteristics of this group include:

  • Endoskeleton (internal skeleton)
  • Water Vascular System (circulatory system)
  • Tube Feet (used for walking or feeding)

Crown of Thorns Characteristics: They are large coralivore starfish with up to 19 legs. Very well protected by their toxic spines.  Only the Triggerfish and Triton Turmpet fish are able to eat and overcome any injuries with this species.

Image removed.
"Crowns of Thorns"

Importance:  In low numbers there are less than 2-3 crown of thorns on a dive site: This helps clean coral skeleton for settlement of juvenile corals and other organisms, which helps strengthen the reef resilience. They can feed on chemicals released by stressed corals and thus remove less fit coral from the reef (much like lions help keep the zebra population healthy by removing the weak or sick animals)

BUT: A high abundances of Crown of Thorns can consume and destroy vast areas of coral leading to decreased diversity and abundance of coral life.

Crown of Thorns are on a rise in many areas due to over-fishing and nutrient input. With less predators and more nutrients in the water, more of the pelagic Crown of Thorns larvae survive to adulthood causing outbreak conditions in the worst cases. You may have noticed around certain sites around Koh Tao where this is currently evident.

WHERE: Mainly on the East Coast of Koh Tao such as dive sites including King Kong Rock, Lighthouse Bay, Hin Wong Bay, South of Twin Peaks.

HOW TO FIND THEM: Look at the Corals and see if you find any scars such as white marks. This indicates that a predator has covered the coral and that they are freshly killed.  At the same time you may find other carnivores such as DRUPELLA SNAILS that also feed on coral tissues.


  • WARNING: Spines are very sharp so we need to have protection and be aware on how to collect this species
  • AVOID: Cutting the Crown of Thorns in 2, otherwise they will reproduce
  • DISTURBANCE: If we collect them incorrectly then they may be disturbed or harmed in which case they may release their eggs and sperm in the water which can lead to re-population of the species
  • This is why we will be using a BUDDY SYSTEM, whereby one person will remain on the surface to collect the bucket that holds one of the Crown of Thorns, which will be taken back to the boat and placed in a fresh water bucket.  Another bucket will be issued to the divers below so that they may continue collecting more Crown Of Thorns.
  • Finally they will be disposed of once on Land.

If anyone would like to Participate in this event, please contact us at Sunshine Divers on to join on the day - 4th September, 2013.

Thanks to Emma for her complete support in this program.

Image removed.
"Presentation by Emma on the Crown of Thorns"













Action Promo Image
Use Your Phone to Take Action for a Clean Ocean
Reporting marine debris just got easier with the Dive Against Debris® app.

Want to Receive Monthly Ocean News and Action Alerts?