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Sunlight illuminates a thriving coral garden teeming with life—a testament to what protection and careful stewardship of coral reefs can achieve. The coral gardens here are a far cry from their former past where the shallows had been exposed to destructive practices like blast fishing
 

Before we see the reef, we hear it—literally. Biologist Julia Mellers scrolls through an audio file pulled from a hydrophone she anchored to the Wakatobi Resort house reef days earlier. The waveform dances across the screen in dense, erratic spikes.

“This,” she says, pressing play, “is what a relatively undisturbed reef can sound like.” A sharp crackle fills the speakers—the collapsing cavitation bubbles of snapping shrimp. Beneath it runs a subtler chorus: low grunts, pulses, rhythmic clicks. Fish communicating across species and frequency. A reef in conversation.

For guests diving Wakatobi’s reefs, this underwater soundtrack is familiar, even if we rarely stop to think about what we are actually hearing. The crackle of snapping shrimp, and the clicks and grunts of fish are more than just atmosphere on a dive. In an era when coral reefs are increasingly defined by silence, bleaching, biomass collapse, and ecological simplification, the soundscape of Wakatobi’s reefs is data. And that data tells a story.
 

Wakatobi’s house reef is a reminder that protection begins close to home
 

A bird’s-eye view of Wakatobi Resort and its beautiful house reef

Measuring What Most Reefs Are Losing

Coral reefs worldwide are under accelerating pressure from warming seas, destructive fishing and industrial fish extraction. Mass bleaching events are occurring with alarming frequency, while fish biomass in many regions has declined precipitously. Yet in a small region of Southeast Sulawesi, where the Banda and Flores Seas converge, the reefs inside Wakatobi’s protected zone are defying those trends. That claim isn’t marketing. It’s measured.

Julia Mellers, who holds a master’s degree in biology from Oxford, UK, leads Wakatobi Resort’s Reef Health Assessment Program. Her mandate is simple but ambitious: quantify reef health. “We’re tracking biodiversity across different elements of the tree of life,” she explains. “Not just coral cover or fish abundance, but using metrics across the ecological network.”

Inside and outside the resort’s privately managed marine sanctuary, the team conducts systematic reef surveys, comparing fish and coral diversity, and looks for signs of stress or degradation. The results are consistent: Reefs within the protected zone show markedly higher benthic diversity and less evidence of damage compared to adjacent unprotected areas.

But this is not something that needs to be explained to us with a data sheet. It is immediately visible once we descend to Wakatobi’s reefs. The density and variety of fish, the presence of herbivores like turtles, and the sheer complexity of life occupying the reef is hard to ignore. What the monitoring program does is put numbers behind our impressions, allowing what we experience during a dive to become part of a much larger picture.
 

Marine biologist Julia Mellers explores Wakatobi’s brilliant reefs looking for a place to place her hydrophone. The data, when recovered, will be incredibly valuable in monitoring the reefs’ health and diversity
 

Julia Mellers inspects the hydrophone she retrieved from the resort’s house reef. This underwater microphone captures the rich soundscape of the ocean and can offer vital clues about reef health and biodiversity

Decoding the Reef’s Genetic Signature

Using environmental DNA—eDNA—the team collects seawater samples and filters out microscopic traces of genetic material from mucus, skin cells and waste. Every organism leaves a DNA signature. That genetic soup is then sequenced and cross-referenced against global databases.

This means even the reef life we don’t notice leaves a trace. We might photograph the reef’s obvious characters—a turtle, schooling fish, or a hypnotic cuttlefish—while countless other organisms remain hidden amongst the corals or pass unseen through the water column. A seawater sample can reveal another layer of biodiversity, recording species that never make it into our images.

Analysis detected signatures of 11 vulnerable coral species. Intriguingly, the rarest coral species were concentrated almost exclusively within the most biodiverse sites inside of Wakatobi’s protected area. And that matters. Rare corals are often among the first to disappear under stress. Their persistence here suggests not just protection, but resilience. In a warming ocean, this is insurance.
 

One of the standout coral features on Wakatobi’s reefs are the giant and numerous sea fans

Artificial Intelligence Beneath the Surface

Processing reef-scale biodiversity data is no small task. There are thousands of images, hours of acoustic recordings, and hundreds of genetic sequences to wade through. To deal with the data more efficiently, the team integrates AI-assisted analysis. Photographs from monitoring dives are fed into systems trained to identify coral genera, estimate cover, and detect early signs of bleaching or disease. Acoustic recordings can reveal changes in the reef’s orchestra that may indicate declining fish diversity.

But the goal isn’t simply to document the reef’s health; it is also to detect signs of stress as early as possible. “We’re taking the reef’s pulse consistently throughout the year,” Julia explains. “If something changes—temperature stress, altered fish communication, altered species presence—we aim to see it early.” And early detection is everything.
 

An anemonefish photographed using a deliberate slow shutter showcasing the movement and the rhythm of life on Wakatobi’s protected reefs
 

Green sea turtle in a sea of light: This effect is created by using a macro lens with a wide aperture, and by allowing tiny particles in the water to catch the edge of the strobe light

Why The Reefs Here Are Different

Protection alone doesn’t explain the healthy condition of Wakatobi’s reefs. Geography also plays a role. The region sits at a dynamic confluence where currents from the Banda and Flores Seas meet. This interaction drives upwelling, circulates nutrient-rich water and transports larvae across reef systems. New recruits arrive, populations replenish, and genetic diversity remains high. A barrier reef roughly 10 miles to the west also helps dampen heavy swell, further stabilizing the ecosystem.

These currents are also part of the reason diving at Wakatobi can feel so different from one dive site to another. Water movement, visibility, reef structure, and the species we encounter on our dives here can change across relatively short distances. For us, these variations are simply part of exploring Wakatobi’s magical underwater world; for the monitoring team, they are variables that help explain why some reef communities thrive in particular locations.
 

Fed by nutrient-rich waters, soft corals bloom in the shallows at Wakatobi
 

At Sawa Utara, the reef drops into deeper water, where healthy coral communities continue to thrive

The Biomass Effect

One of the most striking indicators of reef health is fish biomass. Within Wakatobi’s protected areas, fish populations seem to have rebounded dramatically over decades of enforced no-fishing agreements. Larger predators have returned, while herbivore populations remain strong, grazing algae that can otherwise smother coral systems.

Outside the resort’s privately managed marine sanctuary, fishing is allowed to continue and local communities benefit from a measurable spillover effect as fish numbers swell beyond protected boundaries, supporting local fisheries while maintaining core breeding populations inside sanctuary waters.
 

Climate Resistance—Not Immunity

Perhaps the most encouraging point is that during recent widespread global bleaching events, Wakatobi experienced no significant bleaching across its monitored sites. But that does not mean the reefs are immune to climate change. “It means they are buffered—for now,” Julia says. “High coral diversity, active water exchange, and reduced local stressors seem to create conditions that enhance the resilience of the reefs here. When global heat stress hits, reefs that are also not simultaneously having to battle overfishing stand a far better chance of recovery.”
 

Green sea and hawksbill sea turtles can be found on many of Wakatobi’s reefs. Green sea turtles particularly enjoy the resort’s house reef, where they descend onto their favorite chill-out spots like planes landing at a busy airport. They are important reef gardeners, grazing algae that can otherwise smother coral systems
 

Like an underwater rose garden, this stunning formation of hard corals flourishes on the reefs of Wakatobi and is proof of the longstanding protection efforts that allow such delicate structures to thrive

A Protection Model That Keeps Growing

What strikes us most about Wakatobi’s marine sanctuary and Reef Health Assessment Program is that it isn’t static. We were here just 12 months ago, and we can already see much has improved. The resort’s privately managed protected area has grown by another 10 kilometers, bringing the total area to 70 kilometers of protected reef. Another 50 local fishers have also joined the no-fishing and monitoring program as “Reef Guardians,” bringing the number involved in patrolling and protecting the reefs to more than 170 individuals.

That growth is important. It shows that the choice to protect the reefs here wasn’t simply established decades ago and left to run. The program is continuing to evolve, expand, and involve more communities who live alongside these reefs. The model is simple: Make a healthy reef economically valuable to the people who depend on it, and give those communities a direct reason to protect it—creating a direct connection between a healthy reef and a healthy and proud local economy.
 

Jumna (front) and his colleagues: These men no longer fish their traditional fishing grounds but instead under a “reef lease” arrangement with the resort now patrol the area and protect their traditional fishing grounds from fishing activity
 

Teaching Machines to Listen to the Reef

This year, Julia and the team are taking their acoustic monitoring a step further. Instead of simply recording the sounds of the reef, the team wanted to know exactly who was making them. It’s currently possible to use underwater acoustic monitoring to tell that a reef is noisy, or that certain sounds are likely to come from fish, snapping shrimp or other organisms. By matching sounds from the hydrophones to known fish vocalizations, the team also hope to be able to tell which species are present in a recording.

The ambition is to use observations to train AI models, and eventually, hydrophones could be deployed on their own, with the recordings analyzed by the models to identify which species are present simply from the sounds they make. This could transform the way reefs are monitored. Instead of sending divers into the water to photograph, count, and identify fish manually, hydrophones could be placed on a degraded reef and a protected reef, record both, and compare their acoustic communities. Or monitor a newly protected site over time and ask a simple question: Does it sound different after a year of protection?

The longer-term vision is compelling: A reef that can effectively be monitored through its own soundtrack!
 

Living fossils of the reefs here, giant barrel sponges thrive and grow to colossal proportions within the Wakatobi marine protected zone
 

The healthy reefs support numerous species of pygmy seahorse, including Hippocampus bargibanti, Hippocampus Pontohi, and this tiny Hippocampus denise

Monitoring as a Moral Obligation

Only a small fraction of the world’s oceans are fully or highly protected. Even fewer are rigorously and continuously monitored. Wakatobi’s approach is not simply to establish a protected area, but to continually determine whether that protection is working. Data validates the reef lease agreements they have with local communities. Monitoring reinforces trust. And, perhaps most importantly, it gives their communities tangible evidence that protecting their reefs is worthwhile.

There is, of course, another way to determine if their protections are working—by getting in the water. Having dived Wakatobi’s reefs on numerous occasions, we have seen firsthand what a healthy reef looks like. But what struck us most on this visit was how clearly the experience of diving is connected with what Julia and the team are measuring. Biodiversity, fish abundance, and coral diversity aren’t abstract indicators when you’re looking at them through a dive mask—they are the reef in front of you.

As the hydrophone recording fades and the sound file ends in a final crackle of shrimp static, we understand the importance of a reef that speaks. We’ve also realized there is another measure of a healthy reef—whether the people protecting it are still willing to expand the effort. And Wakatobi is doing exactly that.
 

The thriving shallow-water soft coral reef at Tanjung Patok is a powerful example of Wakatobi’s protection model in action—where long-term monitoring, local community involvement, and careful management helps these reefs to flourish
 

About the Authors: Based in Melbourne, Australia, Anita Verde and Peter Marshall have a passion for the planet’s wild places, and through their images and narratives hope to inspire better appreciation and protection of the natural world. When not underwater, you’ll find them on a mountain somewhere. To see more of their work, please visit their website, www.summitstoseasphotography.com.