Want to be an underwater superhero?! That’s what it feels like to participate in crown-of-thorns removal.
The crown-of-thorns seastar (Acanthaster planci) is a corallivore, meaning it consumes coral and does so at a rate of roughly 6 square meters per year (more during spawning season, less if immature). Outbreaks of crown-of-thorns (COT) are devastating reefs through the Indo-Pacific region to the point that a single reef might have hundreds or thousands of COTs, which consume coral faster than it can grow back. The COTs leave behind a barren trail of white feeding scars where there was once healthy coral. The origin of such outbreaks is thought to be an overfishing of predators such as Triton snails, Humphead wrasse, and Titan triggorfish as well as an enhanced larval survival perhaps the result of elevated water nutrient levels.
COT outbreaks and the corresponding management efforts have been documented since the 1960s in primarily Japan and Australia. Australia recently even developed a robot to target COTs. http://www.gizmag.com/aquatic-robot-autonomous-killer-starfish-barrier-reef/39254/ In small coastal communities COTs wreck comparable havoc, however effective and cost efficient management efforts have not yet thoroughly explored, particularly in the Philippines.
My research project will explore existing COT awareness levels, management efforts, and removal success in small coastal communities throughout the Philippines to help such communities improve their response in the future.
To complete my research project I often get the opportunity to play the part of underwater superhero. Donning my mask, fins and snorkel and equipped with kitchen tongs and a floating wash basin aside a Filipino fisherman equipped with his own wooden goggles and single large, flat fin tied on with bits of elastic rope we dive down in search of COTs. Scanning the reef for fresh white feeding scars is the giveaway sign that a COT is nearby often hiding under a coral ledge. On some reefs we have barely enough time to breath as we collect COT after COT, scooping them up with our kitchen tongs and filling our floating wash basin. In the past year we have collected over 10,000 COTs amounting to 60,000 square meters of coral reef saved from consumption! After we bring the COTs to shore they are buried on the beach above the high tide line.
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
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.
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:
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!
SJ Byce as a Peace Corps Volunteer in the Philippines. And Intern at CIEE Bonaire '17