Grab a mask, snorkel and some fins, and swim out from the beach at Pemuteran, Bali, and you will spot something quite unusual beneath the waters of the calm bay. Dotted across the seabed are fantastic sculptures and geometric shapes, fashioned from thick wire twisted into frames and covered in hard and soft corals. These structures - known as Biorocks - may well prove to be an ingenious technique to rehabilitate damaged coral reefs.

The Biorock process - developed by Wolf Hilbertz and Thomas Goreau - involves passing an electrical current through a metal frame placed on the seabed. The process is simply the electrolysis of seawater, whereby electricity is used to promote the deposition of calcium carbonate and other minerals, which build up on the surface of the metal. Hard corals quickly bond to this material and the process is also thought to accelerate coral growth by up to four times. The resulting 'reef' of hard coral soon attracts other inhabitants. Biorock structures have been used in the Maldives, Indonesia, PNG, the Seychelles, Japan, the Caribbean and the Pacific, and the process has been touted as a way to rehabilitate damaged reefs in all tropical areas.

At Pemuteran, Bali, Indonesia, the Karang Lestari Reef Restoration Project has installed many Biorock structures in an area of coral reefs damaged in the past by destructive fishing practices and coral bleaching.  Tourists can sponsor a coral colony receive yearly photos of their colony so they can watch the coral grow. In October 2012, Thomas Goreau of the Global Coral Reef Alliance installed an experimental wave generator used to power a Biorock structure in the bay.  This project is the first of its kind in Indonesia.

A biorock sculpture in Pemuteran
“Under perfect water quality conditions corals grow as fast as they are capable of. As long as the water is not too hot, not too cold, not too muddy, not too polluted etc.” - Thomas Goreau, during an interview with ZuBlu 2017

“Other methods of coral reef rehabilitation such as using wire meshes simply stabilise the coral so it doesn't roll around - they will then continue to grow as long as the conditions are good.  But what is killing corals is that the conditions are no longer good. An extreme event will wipe them out and so these people have wasted millions of dollars in funding and all their corals die when it gets too hot, too polluted - they all die!  Ours stay alive because what we are doing is creating the fundamental biophysical conditions under which all life makes biochemical energy. That is, having about a one tenth of a volt difference between the outside of the cell and the inside. Every cell has a membrane potential and in order to maintain that gradient, in order to make ATP and nADP, cells have got to pump hydrogen ions and sodium and potassium and that is energetically expensive.  In effect, we are giving the coral cells that for free.

“Furthermore, electrical fields are very involved in cell membrane healing. To give an example, one of our students took staghorn coral tips from a single coral colony so they are genetically identical, and put some on the Biorock, some on controls.  He got 4-fold faster growth on the Biorock than his controls. But the things is, the control corals released mucus for two weeks after being transplanted - which is normal for an injured or broken coral. The ones on the Biorock released no mucus at all - essentially, they healed right away.  And if you look, you can actually see their attachment beginning to overgrow the substrate within days.

“So we greatly enhance healing, we greatly increase survival.  For instance in the Maldives in 1998 we had, depending on the site, between 16-50 times higher survival of corals - thats times, not percent - than reefs nearby.”

A dive amongst the Biorocks at Pemuteran is a lesson in how successful this method of restoration can be. The site known as Rock Garden lies just off the beach in front of Taman Sari resort, and features a towering pinnacle of coral and rock that reaches from close to the surface down to 15m.  In the shallows to the west of this pinnacle was a garden of soft and hard corals, however this whole area suffered heavily in the past from both destructive fishing practices and during the El Nino event in 1998. Today, the main attractions are the many Biorock structures that have been put in place.  In total, over 50 different structures have been now been sunk around Pemuteran Bay. The contrast between the degraded reef close to Rock Garden, and the flourishing corals and fish life around the structures is remarkable. Staff from Kerang Lestari can take visitors on a snorkeling tour of the structures and it is possible to go out with the staff on a dive to watch them work on the structures themselves.  The structures themselves come in all shapes and sizes and most of the old ones are now completely covered in both hard and soft corals.

Divers at Pemuteran

Over on Gili Trawangan, the Gili Eco Trust has also established a large number of Biorock structures and hosts a biannual Biorock workshop.  Some of the older structures are now close to 10 years old and have collapsed under the weight of corals, but other, newer structures are still standing and several research plots with coral nurseries can also be seen. These Biorock structures shelter plenty of life including giant frogfish and small schools of razor- or shrimpfish.  Cuttlefish, octopus and scorpionfish are also easily found and the site is also one of the best places to find ghost pipefish and perhaps seahorses in the algae growing in the shallows.

A manta ray Biorock structure in the Gili Islands

If you are interesting in learning more about Biorock or would like to make a donation to the Gili Eco Trust or Karang Lestari, please use the links below: