Everything in the ocean is connected in some way. From the smallest krill to the largest whale, these marine ecosystems need balance at all times for their species to survive. We talk about it all the time, but seeing it for yourself is an entirely different thing. Understanding that the ocean relies on this symbiosis opens your eyes to the role we must play to keep that intact. Today, offering even more opportunity to see this first-hand is needed to drive the necessary behavior change that will keep the ocean alive.
When we think of “the best tropical diving,” our minds immediately go to the Philippines. But almost always, where there’s beauty there is risk of destruction. And the marine ecosystems here are as beautiful as they are fragile and vulnerable.
When deciding where to explore in the Philippines, we were in search of something specific. We wanted to meet teams that had found a way to balance unbelievable pelagic marine encounters with the best diving conservation practices. This juggling act is one of the most critical to get right, as it’s one of the best ways to equip the emerging generation of divers with the knowledge and skills needed to dive sustainably.
With this goal in mind, we came to meet Matt Reed of Evolution Diving, situated in the heart of Malapascua, Philippines. Matt is the definition of an expert when it comes to navigating these parts, there’s no question about it. He and his team have built an incredible operation since 2010 that trains divers to get as proficient in the water as they are—if not to surpass them entirely!
Malapascua, in the archipelagic province of Cebu, is located about 6.8 km (4.2 miles) from the mainland and accessible via a 45-minute boat ride from Maya Port. But, getting to Maya Port is not alway the easiest. This trek from Cebu City to the far north of the island is a hefty drive, winding through Filipino towns with tiny populations. Out on the Visayan Sea, the small, 2.5 km (1.5 mile) long island is characterized by its white sandy beaches, local villages and diving. It’s all about diving.
The Monad Shoal, an underwater plateau, was notorious in these parts as the best location to spot thresher sharks year round. However, more recently the location’s threshers are seen less ubiquitously than they have been historically. This could be due to other invasive species entering the scene, increased tourism or other human-related issues that tend to plague the ocean.
What’s so special about this area is not only the threshers, but the surrounding coral gardens and the island's proximity to the Mactan-Cebu and Kalanggaman Island. From multi-colored soft and hard corals to macro life that’s undeniably epic, Malapascua has got it all.
Like most people, we were venturing to Malapascua to learn about these threshers. They are one of the most exciting and incredible animals to see in the wild. But there was another, more urgent matter, that we were even more excited to get stuck into—literally. The “crown of thorns” starfish, referred to more colloquially as COTS.
COTS, or Acanthaster planci, is a unique and beautiful, yet destructive, inhabitant of coral reef ecosystems. Recognizable by its spiny, venomous exterior and 21 radiating arms, COTS has a distinct appearance that masks its harmful impact on coral reefs.
The largest starfish in the world feeds on coral polyps by secreting a digestive enzyme that covers its coral prey. It then absorbs the softened coral tissues until all that’s left behind are white scars of coral skeletons in their wake. Although this process is a natural and essential component of the ecosystem that ultimately aids in promoting coral diversity, an overpopulation of COTS can have devastating effects.
Their populations are generally regulated by a variety of factors including predation, disease and availability of food sources. The only predator to the COTS is a triton shellfish, but they have been diminished over the years due to shell hunting and fishing.
Certain conditions, such as increased nutrient runoff from coastal areas, can lead to population explosions, known as outbreaks. These outbreaks can result in the loss of vast expanses of coral reefs, as the starfish consume more coral than can naturally regenerate. The destruction left behind affects not only the structural integrity of the reefs, but also the diverse marine life dependent on these corals for habitat and food.
The life cycle and reproductive habits of COTS also contribute to the rapidity and extent of these outbreaks. Females can release millions of eggs during the spawning season, leading to a sudden increase in their population if conditions are favorable. Efforts to control and manage these outbreaks include manual removal, such as injecting the starfish with death inducing vinegar, minimizing their harmful impact on the reef ecosystems.
After a few incredible back-to-back dives getting accustomed to the flawless waters of Malapascua, we were ready to go after the starfish. It’s so uncommon that you find a dive team like us, killing off a beautiful creature like these. But, an outbreak was in full swing and it was impacting the reef to an extent that was visible even to us transient divers, let alone to those who call Malapascua home.
Matt and his partner, David Joyce, are technical diving pros and have been at it for nearly 25 years. Technical diving stands distinct from recreational diving due to its advanced and specialized nature, allowing divers to explore beyond the typical limits of recreational diving. It involves the use of specialized equipment and techniques to safely navigate environments that are generally considered out of reach for the average diver, such as deep ocean depths, caves and shipwrecks.
While recreational diving typically adheres to no-decompression limits and a maximum depth of 40 meters (131 feet), technical divers utilize mixed gasses, decompression procedures, and often a combination of multiple gas tanks to safely explore depths exceeding this range. Given the increased risks and complexities associated with technical diving, comprehensive training, experience and a strong focus on safety protocols are essential.
In order to manage the COTS population, there were a few critical steps we needed to take. First, we filled up reusable syringes with vinegar—a substance while innocuous to the general environment is lethal to the starfish. In our dive buddy pairs, one held a bag for the discarded syringes that would need to be filled up for the next dives, while the other held the filled syringes. We would pass back and forth underwater.
We were taught a specific method of injection to ensure the vinegar would result in a fatality, as these creatures were fairly sturdy. Each buddy team would demo how to inject correctly. We’d also had to be extremely cautious not to touch the starfish, due to their venom.
Next, we’d drop down and search for the active starfish eating coral. We’d hover so that we were not touching the reef, but could still get close enough to the hard to reach places where the starfish lived. Once we were in the right position, we’d uncap our syringe and inject the starfish between the radiating arm. Always remembering to not accidentally inject ourselves with vinegar!
For the big ones we’d have to use an entire syringe, while for smaller ones only half. The final and most important step was to remove the starfish from the coral, flip it over so that its base was exposed, and let the fish feed on it, inciting the circle of life.
The prevalence of COTS was extremely high while on-site. During one of our dives, all 50 syringes dropped down were used. That meant we encountered nearly 100 COTS during a single dive, a stark reflection of the infestation problem at hand.
Evolution is tasked with the monumental job of managing this outbreak, and any future outbreaks to come—a consequence of the broader climate crisis and ecological imbalance. Each dive we encountered served as a tangible reminder of the immediate threats facing our marine ecosystems. The situation at Malapascua is a microcosm of a global challenge, driving home the urgency of addressing environmental changes to safeguard the oceans' future.
It’s not just here where outbreaks are happening. Places like the Great Barrier Reef, Thailand, the Pacific Islands and Japan are seeing COTS in mass. Beyond manual injections, efforts to mitigate COTS outbreaks also include broader initiatives addressing water quality and reef resilience. It’s clear that the global nature of COTS outbreaks underscores the need for international cooperation and holistic approaches.
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