Indonesia: Bali: Pemuteran Coral Reef Restoration Project


Twenty eight Biorockâ„¢ coral nursery structures have been installed in the Pemuteran Village Marine Protected Area in Northwest Bali, Indonesia, making this the largest Biorockâ„¢ coral reef nursery and restoration project worldwide. The nurseries are welded steel matrices that are electrically charged via two electrodes supplying low-voltage, direct current from an onshore site. The submerged electrodes generate electorlytic reactions that cause minerals naturally present in sea water to accumulate on the Biorockâ„¢ structures. This mineral accretion produces natural limestone–the material which also constitutes coral skeletons, reefs and sand–and fosters the settlement and rapid development of corals, coralline algae, bivalves and many other organisms. After initial success in facilitating the re-colonization of most local coral species, project practitioners expanded the restoration area and have installed additional nurseries in several phases. Seen as a way to mitigate the destruction of important fisheries and stimulate ecotourism in the region, this ongoing project is conducted with the support of the Municipality of Pemuteran, Gahawisri (the Balinese Watersports Federation), local dive shops and hotels, and other local stakeholders.

Quick Facts

Project Location:
Pemuteran Village Marine Protected Area, -8.168066, 114.64898059999996

Geographic Region:

Country or Territory:


Coral Reef, Seagrass & Shellfish Beds

Area being restored:
2.4 hectares

Project Lead:
Pemuteran Bay Coral Protection Foundation (Yayasan Kerang Lestari Teluk Pemuteran)

Organization Type:
Community Group


Project Stage:

Start Date:

End Date:

Primary Causes of Degradation

Climate Change, Fisheries & Aquaculture

Degradation Description

The destruction of Bali’s coral reefs has resulted from human activities, such as dynamite and cyanide fishing, over-exploitation, and environmentally-unfriendly tourism, as well as environmental factors, such as pollution, increased turbidity, and global warming. Destructive fishing practices employing bombs and cyanide have been widely utilized in the region, as the low currents of Pemuteran Bay make it easy for fishermen to retrieve dead fish. These practices have turned offshore bank reefs that were once dense thickets of coral packed with swarms of fishes into barren piles of broken rubble.

Anthropogenic stressors have been complicated by changes in water temperature associated with climatic events. The 1998 El Nino incident, which raised water temperature worldwide, caused a phenomenon called bleaching in which the coral dies due to the increase in temperature, giving the visual effect of the reef being bleached. The impact of changing water termperatures, coupled with destructive fishing practices, has left Pemuteran’s reefs severely degraded.

Project Goals

To increase coral growth and recruitment rates and increase the densities of reef fish by providing them with suitable natural habitat.


The project does not have a monitoring plan.


The Pemuteran coral reefs are a vital source of livelihood for both fishermen and members of the ecotourism sector. Consequently, this restoration has been conducted in close collaboration and cooperation with local partners ranging from fishermen, divers, hotels, marine parks, environmental organizations, and community groups. An attempt is made to demonstrate the full range of factors affecting their reefs and to propose solutions and strategies for their effective management.

Description of Project Activities:
The coral nursery structures are made of welded construction steel bars, mainly of 1 centimeter and 1.3 centimeter diameter. They are built in a variety of shapes. One structure, called the Nautilus, is 3.5 m high 3 m wide, and 11 m long, in the form of an ellipsoidal pyramid. Six structures, called the Flowers, consist of funnels of about 2.5 m high and 3-5 m diameter. These structures have numerous arc-like pockets along their sides. Another set of 7 structures, called the Caterpillars, are 12 m long, about 2 m wide and 2 m high, and consist of open downward and upward pointing arcs. Two structures are bamboo-steel composites, composed of 12 m horizontal bamboo logs, with steel bars driven through their length, supported by steel arc legs. One structure has a single length of bamboo, while the other consists of two such units end to end. Another structure, the Big Bamboo, is built only of bamboo, wrapped with 2 mm copper wire. Following application of electrical current, the steel structures proceed to grow a white limestone layer, providing a substrate for coral growth. While the bamboo elements are not electrically conductive, the steel bars inside them or the copper wire around them grow limestone on their surfaces, which is expected to mineralize the adjacent bamboo wood over time. Another project consists of mesh, 1.2 m wide and 25 m long, laid over the bottom. An additional project on the other side of the bay in front of Reef Seen Aquatics uses wires directly attached to corals. All structures are charged by power supplies located at adjacent onshore sites. They are located in two enclosures at Taman Sari Hotel, in Archipelago Dive shop at Taman Sari, in the Pemuteran Village Barong Art Shop, in Yos Dive Shop at Pondok Sari Hotel, and at Reef Seen Aquatics. Electricity is donated by the operators of these facilities. The cathodic structures and anodes are connected to the power supplies by cables which are buried in the beach and laid on the sea floor. All the structures combined receive up to about 4.5 kilowatts of power annually. Many structures receive power through several cables, and all are wired to each other so that power is shared throughout, allowing them to continue operating even if their direct power cables are severed. The power supplies are wired in parallel through common buses, so that if one fails the others will take up the load. As a result of this redundant design, the system is highly robust to failure of any particular cable or power supply. Corals were collected for transplantation onto the structures from sites in the Pemuteran area, including sites within the protected area and nearby fringing and offshore reefs. Corals were transported in large plastic buckets filled with seawater and attached to the structures as soon as possible. Most corals were simply wedged into specially designed spaces between the structural elements of the nurseries, and needed no further attachment. Other corals were attached by wires, or placed on or next to the structures. Coral selected for transplantation consisted almost entirely of naturally broken fragments that were found lying on reef slopes or buried in mud below them. Large numbers of corals were found loose, often having had their bases undermined by boring worms, clams, and sponges. Many of these corals were previously severely damaged by abrasion or burial, often with significant fractions dead. The purpose of choosing these damaged fragments was to rescue corals that would have almost surely soon died as the result of physical injury, and to avoid damaging healthy corals whenever possible. Often only a very small fraction of the coral was left alive as a result of previous injuries, but in almost all cases these living portions proceeded to grow well after attachment. A few totally dead corals were attached because some divers involved in collection were insufficiently experienced at identifying live corals. Although the focus was on stony reef-building corals, some soft corals, sponges, tunicates, and anemones were also transplanted. The naturally generated coral fragments most likely to be found by divers tended to be the most abundant branching corals (primarily Acroporas, Pocilloporas, Porites, and Seriatoporas). Consequently, these species tended to be over-represented in the collected transplants. A special search was made for rarer coral species unlikely to be found as natural fragments, such as massive or encrusting corals. Where these could not be found loose, small fragments were broken off and transplanted to ensure that the maximum species diversity of the area was represented. These were often taken from colonies growing near the structures. Some massive and cryptic encrusting corals found in the area were never found in sizes or shapes that could easily be broken off and transplanted, and are therefore under-represented on the structures.

Ecological Outcomes Achieved

Eliminate existing threats to the ecosystem:
At least 66 of the 82 reef building coral genera in Indonesia (80.5%), and of the 111 genera worldwide (59.5%), are already being cultivated on the Pemuteran Coral Arks. It is likely that several more genera are also found on the nurseries but were not identified, especially cryptic encrusting species on the undersides of other coral colonies. Coral nurseries receiving adequate power from the submerged cables quickly turned white from mineral accretion and began to cement themselves to the reef bedrock. Almost all live coral fragments were quickly cemented in place by the accreted minerals and proceeded to grow rapidly over the Biorockâ„¢ structures. New coral skeleton growth was clearly visible in as little as a few days. Because these corals have only recently been transplanted and the power applied, it is too soon to compare detailed differences in growth rates between species; but even in the first few weeks some trends became apparent. The Acroporas and Montiporas seem to be most responsive, quickly overgrowing the mineral accretion, often completely growing around it, and rapidly forming dense arrays of new branches. Some Acropora colonies formed hundreds of new branches that grew about a centimeter in less than a month, and many corals show clear changes in growth orientation and unusually dense and compact branching after transplantation. These corals are also distinguished by very bright colors. Following the establishment of new coral growth on the structures, fish and marine invertebrates began to be rapidly attracted wherever the corals were sufficiently dense. Large populations of many small reef fish that live only around living corals quickly found the coral transplants and established themselves. The presence of many juveniles and rapidly increasing populations of these species indicate that they have become self-sustaining populations. Dense schools of young fishes of many species were observed to be attracted to the mineral accretion corals, apparently choosing them as sites to metamorphose from larval stages into juveniles. Snappers quickly found the structures an attractive place to hide in the day time, forming schools so dense that it was often impossible to see the other sides of the structures. Batfish also became regular inhabitants. Damsel fish and cleaning fishes quickly established territories on the structures. Other species of reef fish come to graze on the thin coating of algae growing on the less charged structures, and many other species simply pass through them in their search for food. Most fish species appear to be attracted by the electrical currents, and none to be repelled. In addition many invertebrates, including attached tunicates and mobile squid, cuttlefish, sea urchins, and starfish, have established themselves at the sites.

Factors limiting recovery of the ecosystem:
Only very low levels of coral mortality were observed. Some was due to corals that were dislodged from the structures by waves, divers, or fish before they were fully attached. Some corals were so severely damaged before transplantation that they died of their injuries. Other corals were infested with the coral-eating snail Drupella, which can quickly kill colonies if they are not removed. These were found in swarms of plague proportions on the reef, and are currently the major cause of coral mortality. Some coral species appeared to have minimum sizes for successful transplantation. While most pieces as small as a few millimeters across were successfully transplanted, some of the larger polyped corals appear to need larger areas of tissue to be successfully transplanted. Certain species of thin leafy corals or delicate branching corals proved to be hard to transplant because they tended to break while being attached. Some corals that were collected in deeper areas or on walls bleached when transplanted into shallow water, but most recovered in a few weeks. Only a tiny handful of corals were observed to die for no obvious reason, and it is possible that these were diseased. There was no species of which at least some fragments did not successfully attach and grow. Due to the need to replace faulty cables, coral transplantation was greatly slowed down, and most structures have far too little coral on them. Because of faulty cables, many of the structures were receiving insufficient power until this problem was corrected. The corals on these structures were notably less vigorously growing and less brightly coloured than those structures receiving full power, and the mineral accretion on these structures tended to build up a dark surface layer of algal growth that was not apparent on those fully charged, which were white in appearance.

Socio-Economic & Community Outcomes Achieved

Economic vitality and local livelihoods:
Sustainable eco-tourism requires the protection of natural beauty, yet conservation often conflicts with traditional users of the same habitats. For example, fish become more valuable when they can be seen again and again by divers and snorkelers, "paying" for themselves many times over, whereas their value for a fisherman is only equivalent to a single meal. In an attempt to reconcile these competing interests, hotels, dive shops, village fisher folk, scientists, and conservationists have united in Pemuteran to protect and restore coral reefs and thus to increase ecosystem resources for both tourism and fisheries. By restoring and protecting their reefs and aiding in the recovery of fish populations, the residents of Pemuteran stand to gain much from a vibrant ecotourism industry and healthy, sustainable fisheries.

Key Lessons Learned

Even in the earliest stages, these projects show dramatic results in increasing coral growth and fish populations. The projects are also a major attraction for divers and snorkellers. They show great promise for restoring damaged coral reefs and need to be applied on a large scale wherever coral reef deterioration has been seen, especially across Indonesia, as it is the centre of tropical marine biodiversity. Biorockâ„¢ nurseries have the potential to play a significant role in maintaining coral reef ecosystems in the face of accelerating threats from global warming.

Long-Term Management

With regard to the management of the actual Pemuteran structures, the corals and their growth need to be periodically monitored by video, at least twice a year, and if possible four times a year, to get a handle on seasonal changes. The stimulation of coral growth is likely to vary strongly between different coral species and between structures receiving different amounts of current. Therefore it will be especially important to monitor the growth of all the corals on all the structures in order to determine which species do best under different rates of charging. Growth rates should be monitored from time to time using video images. Many of the coral fragments transplanted came from known nearby colonies, and both the transplants and the mother colonies need to have their growth monitored to allow determination of the amount of growth enhancement from mineral accretion. In addition it will be important to try to transplant and cultivate the fullest range of local species, including those that are still under-represented or absent from the structures.

The best results will come with periodic maintenance. Power supplies need to be checked, cables need to be kept buried in the ground where they cannot be damaged, and cables in the wave breaking zone need to be kept sheathed in PVC pipe to prevent rubbing on rocks and breaking during storms. Corals that are broken or dislodged should be promptly repositioned, and coral eating pests, such as crown of thorns starfish or Drupella snails need to be removed. Structures should be periodically inspected to ensure that they are growing well and that they are receiving the electricity they need to function properly.

To prevent future destruction of the reef by harmful fishing practices, a community educational program was initiated in order to encourage local users to assume responsibility for their own reefs and marine resources. As part of this effort, a program of coastal security has been established with daily patrols to control bombers and poison fishing. This is the first program of its type in Indonesia, and the Pemuteran fishermen, with help from the local police, have already stopped several groups of bombers and poison fishermen on the outer reefs.

Although climate change could still pose a threat to these reefs, the Biorockâ„¢ nurseries have been shown to allow corals to thrive, even when water quality conditions have deteriorated to the point of killing surrounding corals. Coral growing on the mineral accretion structure often has a higher growth rate and healthier metabolism, resulting in faster and more prolific reproduction. Hence, these nursery populations tend toward greater resilience to unfavorable environmental conditions and also play a key role in restocking the surrounding reefs.

Sources and Amounts of Funding

The Karang Lestari Project has been conducted solely with private funding and in-kind donations from local hotels (the Taman Sari Hotel the most notable among them), dive shops, and individuals interested in the restoration. There has been no government or NGO funding received (although the Leslie Jones Foundation provided support for a workshop on coral nursery construction), and Dr. Tom Goreau and Prof. Wolf Hilbertz have donated all their time, travel costs and many of the materials needed for the project. Taman Sari Cottages has donated room and board for project participants, and Archipelago Dive has donated the use of diving equipment and boats throughout. The electricity needed to catalyze mineral accretion on the Biorockâ„¢ structures is being donated by several local businesses.

Other Resources

Global Coral Reef Alliance

Pemuteran Project Contact


Professor Wolf Hilbertz, Biorockâ„¢ Inventor
Email: hilbertz@emirates,

Primary Contact

Organizational Contact