how-the-earthquake-affected-the-reefs-of-the-gili-islands

The Impact Of the Earthquake On The Coral Reefs Around The Gili Islands

When the earth shook

As most of you know, on August 5th 2018, the earth shook in North Lombok, Indonesia. An earthquake with a magnitude of 6.9 on the Richter Scale caused major damage to the mainland and affecting the surrounding areas including our home, the Gili Islands. Following this, a series of earthquakes continued to shake the region until the end of August 2018.

Finally, on September 1st, the Gili Islands were declared by the government safe to travel again. Among all the questions hanging on every traveler and diver’s lips, one subject was recurrent. ‘How is the diving now?’, ‘Has the reef changed?’, ‘Can we still dive?’. And some other silly questions like: ‘are all the fish gone?!’

diving-around-the-gili-islands


With the Gili Islands being famous for its various dive and snorkeling sites, it’s only common sense that visitors wanted to know how the earthquake has affected the reefs. But they were not the only ones. We, the shark team, more than anybody, were eager to found out and see it with our own eyes. Desiring to see whether mother nature had preserved our beloved underwater world or not.

Going back in the water after the earthquakes

As things slowly went back to normal on Gili Air, regular activities restarted. Oceans5, our affiliate dive centre, was the first to go back to the water starting diving again in late August. And we didn’t miss the opportunity to get back in the water as well. This meant we started assessing the condition of the reef at the beginning of September until the end of the month. A sample of ten dive sites has been in our radar including Sunset Point, Shark Point, Halik, Turtle City, Meno Wall, Meno Slope, Bounty Wreck, Han’s Reef, Myrko’s Reef, and Air Wall.

In order to asses the changes on the reef, we also asked all dive guides and instructors of Oceans5 to share their observations and take pictures of the impact on the reefs around the Gilis. The Oceans5 team has been a great supporter of our data collection!

Let's go diving around the Gili Islands

How did we came out with the results?

In order to assess the impact of the earthquakes on the reef, proper scientific methods were used, as well as considering what we could see ourselves. We used two different methods throughout September at our 10 sample dive sites to understand the changes.

1st method: Roving survey


The first method used was Roving survey. This is a visual surveying method designed specifically for actively seeking out and positively identifying indicator species for 30 minutes. During these dives, we count all indicator species (fisheries targeted species including snappers, groupers, emperors, trevally, barracuda, tuna and mackerel) as well as shark, ray and turtle sightings. We record the number of individuals observed, species information, size estimation, sex of sharks, rays and turtles and the depth and dive time at which we encounter each individual. The more sightings of the targeted species over 30 cm indicates a healthier reef. This is currently observed within the MPA (marine protected areas) around the Gili Islands.

roving survey dive after the earthquake


In addition, we also record observable impacts to the seafloor such as cracks on corals, tipped over corals, and landslides. The details including the size of the impacts (dimension), depth, and orientation of impacts. This method has been conducted at all 10 sample dive site.

2nd method: Fish and Benthic


The Fish and Benthic method is designed to assess reef health. Data on fish species, size and biomass are collected along with the Benthic composition (meaning the invertebrates (organism without a backbone) that live on the bottom of the seafloor). The basic method requires four people, each with their own independent role. Two of the team members count every fish of specific family that is longer than 8 cm on either side of a line for 50 m, which the third team member lays. The fish families include anemone fish, angelfish, butterfly fish, damselfish, goatfish, squirrelfish, triggerfish, filefish, batfish, surgeonfish, parrotfish, wrasse, spadefish, basslets, snapper, chub, jackfish, tuna/mackerel, barracuda, grouper, needlefish, trumpetfish, lionfish, lizardfish, scorpionfish, boxfish, and moray eel. The total area covered by this survey is 250m2. Whilst, the fourth ‘substrate’ team member records the composition of the sea floor every 50cm for 50m.

The depth range of this method is between 6–12 m (shallow reef). The output from this method that is used to calculate reef fish density per m2. Fish and Benthic have been conducted at pre-assumed-impacted dive sites only, including Bounty Wreck, Sunset Point, and Turtle City.

School of fish around the Gili Islands

So, what did we find out about the impact of the earthquakes on the reef?

At 5 of our 10 dive sites we observed changes to the reef due to the earthquakes. We saw 2 types of effects, crack or landslide, determined by the topography and the bottom composition of the dive site. The cracks were found mostly at Sunset Point and Han’s Reef while landslides were found at Turtle City, Bounty Wreck and Meno Slope

As for the indicator species, observed from pre-earthquake and post-earthquake with the Roving Surveys method, there is a decrease of indicator species sightings at Sunset Point, Meno Slope, Shark Point, Myrko’s Reef, and Halik. As for the rest of the dive site sample, including Turtle City, Bounty Wreck, Han’s Reef, Meno Wall, and Air Wall, the indicator species sightings have remained the same.

From Fish and Benthic Surveys, we also saw a decrease in reef fish density at Sunset Point and Bounty Wreck. Similar to Roving Survey results, the reef fish density at Turtle City did not change.

So are all the fish gone?


Despite some cracks or landslides, despite some difference of indicator species and reef fish density at certain dive sites, to our great relief and to answer your question no the fish are not gone. All our main residents are still around!

Green Turtle Gili Islands

Turtle City

As the main attraction of Turtle City, the large group of green turtles at the top of the pinnacle are still constantly sighted every day by SCUBA divers and snorkelers. This observation suggests that despite the change of topography, the main features of Turtle City have not changed.

Sunset Point

At Sunset Point the “usual” white tip reef shark nursery scenery around 21m can still be observed. Similarly, hawksbill turtles are still a frequent occurrence in the shallows of this dive site.

Han’s Reef

Despite some cracks observed at two of the pinnacles, the group of green turtles is still sighted on the top of them, resting at their usual place as reef fish school above them.

Bounty Wreck

Finally, Bounty Wreck’s main attraction, the shipwreck, has not been affected at all. The abundant marine life and the beautiful soft corals growing on the shipwreck are still present and healthy.

What are you waiting for? 

Set aside the fact that the topography of certain dive sites has been affected, the main attraction of the Gili Islands; diverse marine life, turtles, sharks, and rays are still very much present. The Shark Warrior team have even ID’d new turtles recently. We see our resident whitetip reef sharks at Halik, Sunset Point, and Shark Point every time we go. We often spot blacktip reef sharks passing by at Halik, many eagle rays swimming around at Shark Point and Deep Turbo and so, many blue spotted stingrays and blue spotted ribbon-tail rays at too many dive sites to count. And obviously, we continue to see turtles on every single dive!

Whale-passing-by-Gili-Islands


Now may even be a better time than ever to dive in the Gili Islands. As our observations suggest that with fewer boats on the water, meaning less noise pollution underwater, is bringing rare animals to pass by our waters including mobula rays, whale shark and humpback whales. Those three have all been spotted around the Gilis during September. The underwater world is just as beautiful as ever and is just waiting for you to explore! So what are you waiting for?!

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