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Restoring bleached coral, the Banda way

Updated: Aug 22, 2022

The Banda Islands (Kepulauan Banda) are a group of small volcanic islands in the Banda Sea, in the western Pacific Ocean. South of Seram Island, east of Java, west of Papua, and a long way north of Australia, they fall within the Indonesian province of Maluku. Historically significant because of nutmeg, it is the underwater beauty that attracts attention today. Sadly, despite the remote location, coral bleaching occurred in 2020. Thanks to funding by Deutsche Stiftung Meeresschutz (DSM) in Germany, an innovative test project by local students is underway, aimed at restoring the bleached corals with larvae collected during spawning.

This feature has been provided by DSM. All photographs are by BandaSEA who own their copyright. (Scubavox ed.)

Coral restoration in the Banda Sea, Indonesia

In spring 2022 a new, non-invasive coral restoration project started in the Banda Sea near Indonesia's Banda Islands. BandaSEA (Germany) and Luminocean (Indonesia) provide scientific supervision. Restoration work is being carried out by students at Hatta-Sjahrir Fisheries School Banda Islands, Rifaldi Kadir and Farista Gani. They are testing a simple but effective technique for restoring bleached reefs.

How to restore damaged reefs?

With global coral mortality, restoration is becoming a matter of survival for damaged reefs. However, many coral projects are done without a scientific approach. Often it’s merely a tourist attraction. This can cause more harm than good. For example, coral pieces are obtained for "transplanting" by breaking off corals from intact reefs. There is no analysis whether the recipient reef is suitable at all for any transplanting efforts, such as the impacts of fishing, nutrients or tourist interaction. Thus, one may release the broken-off corals into environmental situations with which they cannot cope. In addition, direct transplantation of broken coral pieces reduces genetic diversity in the recipient reef, as only certain species can be used for this method.

Study area : Banda Islands in the Indo-Pacific Ocean

How to do it better? Simple, yet effective? Without a lot of lab work? Non-invasive?

Rifaldi and Farista want to find answers to these questions. The Banda Islands are located in the middle of the deepest sea in Indonesia, the Banda Sea. With more than 397 species of hard corals and an estimated 695 species of reef fish on a relatively small reef area, the Banda Islands are among the areas with the highest biodiversity in the Indo-Pacific. Thanks to their remoteness, many coral reefs here were still relatively well preserved until 2020.

Coral reef off Hatta Island before coral bleaching

Coral bleaching in 2020

Coral bleaching triggered by the 2020 heat wave hit Banda reefs hard, especially Porites and Montipora corals. Some sites had up to 54% bleached (effectively, dead) coral on the reef top and 48% on the reef crest. This had never happened here before. Some of the most damaged reefs are located off Hatta Island. Until 2020, the highest coral diversity and biodiversity in the entire Banda Sea reef system prevailed here. At Hatta there are hardly any local reef-damaging influences. Fishing and marine pollution play no role. Therefore, the Hatta reefs are the ideal location.

Bleached coral reef off Hatta Island

Household funnels and PET bottles for coral restoration?

One can keep coral colonies in the lab, collect eggs and sperm at spawning and then grow them up (ex situ). This is expensive. It requires a lot of expertise and technology. The Indonesian students are taking a different approach. They collect egg and sperm bundles (gametes) from spawning colonies in situ, in the field. The main equipment for this is household funnels and PET bottles.

On spawning nights Rifaldi and Farista and their dive team attach collection traps over individual coral colonies. No coral is damaged in the process. A check dive is then be made the following day to see if any gametes are in the plastic bottles.

Gamete trap from funnel and PET bottle over a coral

Rifaldi Kadir preparing the gamete traps Rifaldi Kadir and Farista Gani

Gamete trap from funnel and PET bottle over a coral

Breeding coral larvae without laboratory use

The gamete bundles are placed in a 10-liter tank for fertilization. Subsequently, the coral larvae (planula larvae) can develop in a 1000-liter tank in a well-protected environment. The seawater used for the basin and tank is filtered. This is important to prevent algae or other harmful organisms from getting at the little corals.

Tanks for rearing coral larvae

In zip-lock bags to the new home

After about 4 days, the larvae are big enough to be transferred to "real life". For transport simple zip-lock bags are used. In the recipient reef, 3-by-5-meter plots were previously marked over dead coral or rocks. Before releasing the larvae, divers cover each plot with a fishing net double-lined with organza fabric as a "shelter". To prevent the net from drifting, it is weighted with fishing lead.

After 5 days divers remove the net. The markings on the plots make it easy to find them later. This is critical to monitor settlement success over the long term.

Preparing a fishing net with organza fabric Transporting the fishing net to the settlement plot

Divers attach fishing nets with organza fabric to colonize the coral larvae

Success control

The coral’s settlement success is then checked after 1, 2, 4 and 6 months respectively. Comparatively few dives are therefore necessary. Each new coral colony is photographed and measured. A comparison is then made with the plots where no larvae were released.

Specific aims of the project

The goal is also to develop a best-practice guide for coral restorations that are easy and inexpensive to implement while maximizing biodiversity conservation. To date, there is no non-scientific guide written in Indonesian on coral restoration options. Once the method is established and the guidelines made available, local conservation or diving initiatives can use it to independently restore damaged coral reefs, even on remote Indonesian islands.

With a permanently operational larval propagation facility on the Banda Islands, it will be possible to respond quickly in the future when reefs die. This project, supported by young Indonesian divers and students, will also raise awareness in Indonesia of the problems caused by poorly planned and executed coral restoration projects.

Partner websites:

Project funded by:

Farista Gani, student at the Coral Restoration project in Indonesia



A bandaid for the Banda islands! Incredible work, so desperately needed. Great photos, really tells a story.

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