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Crown-of-Thorns Removal in Action

From Sept 25 to October 1, 2015 a team of fishermen, municipal and provincial staff members, and your local Peace Corps Volunteer worked to remove over 250 Crown-of-Thorns (CoT) sea stars from a single reef in Barangay Canduyong, Odiongan, Romblon, Philippines. Here’s the video with English and Tagalog: Crown-of-Thorns Removal

Crown-of-Thorns seastar (Acanthaster planci) feeding on coral.
Crown-of-Thorns seastar (Acanthaster planci) with its numerous arms and venomous spines feeding on coral.
White dead coral skeleton remaining after CoT feed in contrast to the remaining live colored polyps. Over time algae will grow and cover this white skeleton.
White dead coral skeleton remaining after CoT feed, in contrast to the remaining live, brown colored coral polyps in the foreground. Over time algae will grow and cover this white skeleton.
Jerome snags a CoT with tongs.
Jerome snags a CoT with tongs.
It is important to remove CoT from the water immediately because if this animal becomes stressed it will release its eggs as a last ditch effort to reproduce.
It is important to remove CoT from the water immediately because if this animal becomes stressed it will release its eggs as a last ditch effort to reproduce.
Our removed CoT kept high and dry to avoid propagation if its gametes were to be released in the water.
Our removed CoT kept high and dry to avoid propagation if its gametes were to be released in the water.
Removed CoT were buried on land.
Removed CoT were buried on land.

Removing CoT was like working as an underwater superhero! The thrill of working hard to save coral reefs and kill venomous CoT. It was hard to stop once our bucket was full because you would see more and think, “Okay let me just get one more then I’ll go back.”

Now as I prepare to leave for Washington DC and the Blog It Home Winner’s Tour, my office will share the photos and videos of our extraction to educate other Barangays (towns) about the need and process of extraction. We plan to expand our efforts to tackle CoT outbreaks throughout Romblon province.

Crown-of-Thorns

DCIM999GOPRO

The Crown-of-Thorns (CoT) sea star (Acanthaster planci) can pose serious threat to Pacific coral reefs. The CoT varies from traditional sea stars in that it may have anywhere from 7 to 23 limbs and possesses numerous, long, sharp, toxic spines. In normal quantities this invertebrate is an appropriate part of the Pacific reef ecosystem. However, recent, increased, massive outbreaks of CoTs are highly problematic because the CoT is a corallivore, meaning it feeds on coral. Thus, outbreaks have the potential to destroy entire reefs. The CoT eats the fleshy polyps of a stony coral colony leaving behind white scars of the remaining dead calcium carbonate coral skeleton. In a balanced ecosystem CoTs feed on fast-growing Acroporid coral species, however when CoT numbers are abundant they begin feeding on slow growing coral colonies like Porites, which can devastate reefs for many years into the future.

Natural predators of the adult CoT include titon triggerfish (Balistoides viridescens), white-spotted pufferfish (Arothron hispidus), napoleon wrasse, humphead wrasse (Cheilinus undulates), giant triton snails (Charonia tritonis) and painted shrimp (Hymenocera picta). Overfishing of these predators, particularly the Giant Triton, valued for its large, beautiful shell, may have led to increased CoT outbreaks. Furthermore, it is possible that our wastewater and fertilizer have also contributed to these outbreaks. Scientists theorize that nutrient-rich runoff into the ocean from human activities has enabled more CoT larvae to survive, because CoT larvae feed on planktonic algae and an increase in nutrients favors excessive algal growth. Thus more nutrients –> more algal –> more CoTs –> greater damage to coral reefs.

Methods of CoT control:

  • Land Disposal
    • Collect CoTs, handling them with large serving tongs. Bring them to land and bury them.
    • When stressed CoTs will attempt to spawn, therefore it is essential to remove them from the water as quickly as possible.
  • Cutting up and Crushing in situ
  • Tying in bags in water
  • Poison Injection (acetic acid or sodium bisulfate)
    • Injection causes the CoT to disintegrate
  • Using dead CoTs as material for compost has been practiced in Fiji

Currently, we are exploring these methods at my site and will be developing a removal program in the future!