Drupella Sea Snails in Koh Tao: A Hidden Threat to Coral Reefs
When we think about the underwater world in Koh Tao, it’s easy to picture colorful fish, graceful turtles, and vibrant coral reefs. But beneath the surface, there’s a whole network of life working together to keep the reef ecosystem healthy and balanced.
From tiny plankton drifting in the currents to sharks cruising at the top of the food chain, every living thing has its role. This includes some lesser-known creatures, too, like invertebrates, animals without backbones that are essential to reef life.
And one of these small but important creatures is the Drupella sea snail.
Like any ecosystem on land, balance is everything in the ocean. When one part of the system shifts too much, it can affect everything else. Here in Koh Tao, we’ve been seeing an increase in Drupella sea snails. While they are a natural part of the coral reef, their growing numbers are starting to create challenges for reef health. At New Heaven Dive School, through our ongoing reef conservation and monitoring programs, we’ve been keeping a close eye on this situation while conducting diving surveys.
What are Drupella Sea Snails in Koh Tao?
Drupella sea snails are small coral-eating invertebrates, usually around 0-5 cm in size. According to research from the Koh Tao Ecological Monitoring Program (Chad Scott, 2014), they are considered an indicator species, meaning their presence can tell us a lot about the health of the reef. They often live in groups and can have surprisingly long lifespans, sometimes up to 45 years.
In small numbers, Drupella actually plays a helpful role. By feeding on coral, they create tiny disturbances that open up space for new coral to grow. This natural process can increase diversity and support a more resilient reef ecosystem.
When “Helpful” Becomes Harmful
The problem begins when their population grows too large. During a Drupella outbreak, these snails can consume large areas of coral, leaving behind damaged reef structures. This reduces coral diversity, weakens the reef, and can impact all the marine life that depends on it.
There is also growing concern that Drupella may help spread coral diseases, moving from one colony to another as they feed.
Where can you find the Drupella Sea Snails in Koh Tao?
They’re actually everywhere in Koh Tao’s underwater world! While you’re scuba diving, freediving, or snorkeling, take a closer look at the base of the coral reef. If you slow down and observe carefully, you might spot small clusters of purple-pink sea snails gathered tightly around the coral; that’s them, Drupella.
They tend to stay in groups and are often found feeding on coral tissue. You may also notice them in areas where corals are already stressed or bleaching. Seeing them in these spots helps us understand just how much impact they can have on the reef ecosystem, especially when their population grows too large.
How does studying them help reef conservation?
Through ongoing monitoring in Koh Tao, we’re able to track their population, study their behavior, and respond when numbers become too high. By learning more about this small but impactful invertebrate, we can take action to help protect and restore balance to the reef ecosystem. At New Heaven Reef Conservation, removing Drupella has been part of our efforts for many years. But this also raised an important question: what should we do with them after collection?
Over time, we explored many ideas: giving them away, using them as food, even incorporating them into construction materials. Recently, we’ve found a more creative and sustainable approach.
We now collaborate with a local artist who specializes in natural tie-dye. The Drupella shells are mashed and ground down, then used in the dyeing process as an anti-dye (resist) material. When applied to fabric, this paste prevents the dye from being absorbed in those areas, allowing for the creation of patterns, negative space, and intricate designs. It’s also used in traditional batik techniques, adding a unique and sustainable element to the process.
Join us for the Reef Conservation Program in Koh Tao
If you’re curious to learn more about coral reefs, marine life, and the underwater world of Koh Tao, we’d love to share this journey with you.
Our Reef Conservation Program is designed for ocean lovers of all levels. Though the Advanced scuba dive certification is required to join the program, you’ll learn everything from basic reef monitoring techniques to more advanced underwater survey skills.
Feel free to reach out for more information via email (conservation-team@newheavendiveschool.com), Facebook, and Instagram.
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