{"id":18027,"date":"2026-05-02T01:17:13","date_gmt":"2026-05-02T01:17:13","guid":{"rendered":"https:\/\/www.oceans5dive.com\/blog\/?p=18027"},"modified":"2026-05-02T01:17:17","modified_gmt":"2026-05-02T01:17:17","slug":"coral-reefs-gili-islands","status":"publish","type":"post","link":"https:\/\/www.oceans5dive.com\/blog\/coral-reefs-gili-islands\/","title":{"rendered":"Why Coral Reefs Around the Gili Islands Are Changing"},"content":{"rendered":"\n

Coral Reefs Around the Gili Islands<\/h2>\n\n\n\n

The coral reefs surrounding the\u00a0Gili Islands\u00a0have long been among the most accessible and rewarding dive destinations in Southeast Asia. Crystal-clear waters, healthy reef systems, and regular encounters with turtles and reef sharks made these islands a magnet for divers and snorkelers from around the world.<\/p>\n\n\n\n

But if you have been diving here for years\u2014as we have at Oceans 5 Gili Air\u2014you will know that the underwater world is not the same as it used to be.<\/p>\n\n\n\n

This is not a story about one single event. It is a gradual shift, built up over decades. A series of changes that, when put together, tell a clear story: the reefs around the Gilis are under pressure.<\/p>\n\n\n\n

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A Timeline of Change Underwater<\/h2>\n\n\n\n

To understand what is happening today, we need to look back.<\/p>\n\n\n\n

Around the year 2000, divers regularly encountered grey reef sharks around the Gilis. These were not rare sightings\u2014they were part of the ecosystem. But over time, they disappeared.<\/p>\n\n\n\n

In 2008, large groups of mature white tip reef sharks vanished. Again, not overnight, but steadily enough that today, seeing one is no longer the norm but the exception.<\/p>\n\n\n\n

By 2010, zebra sharks\u2014once part of the marine life diversity\u2014were gone.<\/p>\n\n\n\n

In 2015, something else changed. The large schools of bumphead parrotfish, powerful reef grazers that play a critical role in reef health, disappeared from the area. These fish are essential: they control algae growth and help maintain the balance between coral and algae on reefs.<\/p>\n\n\n\n

Then came 2022, when a turtle disease outbreak affected populations around the islands. Turtles, one of the most iconic species of the Gilis, suddenly showed signs of stress and illness.<\/p>\n\n\n\n

In 2025, divers began noticing an unusual increase in Halimeda algae. By 2026, this had escalated into a much larger outbreak, with certain reef areas increasingly dominated by this calcifying green algae.<\/p>\n\n\n\n

And this timeline doesn\u2019t even include global coral bleaching events driven by rising sea temperatures.<\/p>\n\n\n\n

Each of these moments might seem isolated. But they are not. They are signals.<\/p>\n\n\n\n

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What Is Driving These Changes?<\/h2>\n\n\n\n

There is no single cause. Coral reef ecosystems are complex, and when they change, it is usually the result of multiple stressors acting at the same time.<\/p>\n\n\n\n

1. Overdevelopment on Small Islands<\/h3>\n\n\n\n

The\u00a0Gili Air,\u00a0Gili Meno, and\u00a0Gili Trawangan\u00a0are small islands. Their landmass is limited, and so is their capacity to support infrastructure.<\/p>\n\n\n\n

Yet in recent years, development has accelerated rapidly. New accommodations, villas, and resorts are being built at a pace that raises serious questions about sustainability.<\/p>\n\n\n\n

More rooms mean more tourists. More tourists mean more pressure on water, waste systems, and ultimately, the marine environment.<\/p>\n\n\n\n

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2. Coastal Construction and Beach Walls<\/h3>\n\n\n\n

One of the most visible changes above water is coastal construction.<\/p>\n\n\n\n

Beach walls, land reclamation, and building too close to the shoreline disrupt natural coastal processes. Sand movement changes, erosion patterns shift, and sediment can be transported into the ocean.<\/p>\n\n\n\n

Sediment is one of the biggest enemies of coral reefs. It reduces light penetration, smothers coral polyps, and creates conditions where algae can thrive instead.<\/p>\n\n\n\n

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3. Wastewater and Nutrient Runoff<\/h3>\n\n\n\n

As development increases, so does wastewater.<\/p>\n\n\n\n

Without proper treatment systems, nutrients from wastewater seep into the ocean. Elevated nutrient levels change the chemistry of the water, often leading to algal blooms.<\/p>\n\n\n\n

The Halimeda algae outbreaks seen in 2025 and 2026 are not random. They are symptoms of a system receiving too many nutrients.<\/p>\n\n\n\n

This shifts the balance: instead of coral-dominated reefs, you get algae-dominated systems.<\/p>\n\n\n\n

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4. Increasing Numbers of Divers and Snorkelers<\/h3>\n\n\n\n

Tourism is the backbone of the Gili Islands. Diving and snorkeling are at the center of that economy.<\/p>\n\n\n\n

But more people in the water means more potential for impact:<\/p>\n\n\n\n