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Biorock® Mineral Accretion Technology
For Reef Restoration, Mariculture and Shore Protection

What is the Global Coral Reef Alliance?

The Global Coral Reef Alliance is a 501(c)(3) non-profit organization dedicated to growing, protecting and managing the most threatened of all marine ecosystems—coral reefs. We primarily focus on coral reef restoration, marine diseases and other issues caused by global climate change, environmental stress and pollution.

What is mineral accretion?

Mineral Accretion, or the Biorock® process, is a new method that uses low voltage direct current electricity to grow solid limestone rock structures in the sea and accelerate the growth of corals providing homes for reef fish and protecting the shoreline. The electrical current causes minerals that are naturally dissolved in seawater to precipitate and adhere to a metal structure.

The result is a composite of limestone and brucite with mechanical strength similar to concrete. Derived from seawater, this material is similar to the composition of natural coral reefs and tropical sand beaches.

This patented process increases the growth rate of corals well above normal, giving them extra energy that allows them to survive in conditions that would otherwise kill them. At the same time these structures attract huge numbers of fish, and also provide breakwaters that protect the shore and get stronger with age.

Biorock reefs, with their lush coral swarming with fish, have become major ecotourism attractions. Hotels in the Maldives, Indonesia, and Panama have built their advertising around the fact that they can offer great snorkeling right in front of their beaches.

The mineral accretion process was first developed by architect Wolf Hilbertz in order to provide alternative construction materials. He and Tom Goreau of the Global Coral Reef Alliance later developed its use for reef restoration and shore protection. For more information please visit their website http://www.globalcoral.org

Why are coral reefs dying?

Reefs die for many reasons: rising water temperatures, sewage, eutrophication, disease and negligence. A reef ecosystem that took hundreds of years to grow can be destroyed in a single afternoon by dredging, dynamite or cyanide fishing.

Does global warming contribute to coral morbidity?

Corals around the world have been severely affected by global warming. High temperatures cause corals to turn white (or “bleach“). If it remains too hot for too long, the corals die of heat shock.

Record high temperatures are killing corals across the globe, with only a few of the hardiest corals surviving. Mineral accretion has proved to be a remarkable new method that increases coral growth rates and their ability to resist environmental stresses.

What are the consequences of reef morbidity?

When coral reefs die, fish populations disappear; beaches and shorelines are damaged. Unprotected by breakwaters, fragile land areas become vulnerable to erosion, saltwater intrusion and destruction from waves. For an already damaged reef, regeneration is very slow taking several decades, even under ideal conditions.

Why are mineral accretion (Biorock) reefs needed?

Global warming has caused significant reef mortality around the world. The prognosis is that oceans will continue to warm until world leaders recognize the long-term consequences of turning a blind eye to the problem.

A few governments have tried to address the problem by building sea walls out of concrete, steel, coral rubble or sand bags. But these materials soon rust, corrode, collapse and need to be rebuilt. In contrast only breakwaters and reefs made of mineral accretion can provide permanent, cost-effective protection capable of keeping pace with rising global sea levels

How much faster does coral grow with mineral accretion?

Mineral accretion growth rates are typically from one to several centimeters of new rock per year, depending on the surface area of the structure. The rate at which the coral grows depends on the amount of current, the size of the structure and the species of coral. Typically, growth rates are about 3 to 5 times faster than normal.

How do Biorock reefs compare with conventional artificial reefs?

Artificial reefs are typically made from manmade materials like sunken ships, planes, cars, concrete, rubber tires and trash. On land, this material might be called junk. Although fish will hide behind or within any structure that provides shelter and although certain sponges and soft organisms will sometimes settle on these materials, they never turn into a true coral reef.

How is a Biorock reef built?

To build a Biorock reef, an electrically conductive frame, usually made from readily available construction grade rebar or wire mesh, is welded together, submerged and anchored to the sea bottom. Sizes and configurations are infinite and are varied to fit the setting. A low voltage direct current is then applied. (Power sources can include chargers, windmills, solar panels or tidal current generators.) This initiates an electrolytic reaction causing mineral crystals naturally found in seawater, mainly calcium carbonate and magnesium hydroxide, to grow on the structure.

What materials are used in a Biorock reef?

The structure is built from ordinary construction materials typically available almost anywhere in the world. This can include steel rods, pipe, or rebar. Other materials necessary for the project include electrical cables and epoxy or silicone sealants to protect the electric connections. While the main structure serves as the cathode, another electrode, the anode, is a special titanium mesh that does not corrode.

How are Biorock reefs powered?

To power the mineral accretion process, a low DC voltage is necessary. The source of this current generally depends upon the environment near the reef. If a ready supply of electricity is available, cables can be attached to the structure. In more remote areas, solar collectors are usually the energy source. These panels will generally be set up on the shore to feed current to the Biorock reef via submerged cables. Power can also be supplied by other non-polluting sources such as windmills or tidal current generators.

In practice, a low voltage direct current is fed to the reef via cables. The structure acts as a cathode. A special inert material is used as the anode to complete the electrical circuit. The low power is completely safe for swimmers and marine life.

How do you anchor a Biorock reef?

In most coral reef environments, structures sit on limestone bedrock where they eventually cement themselves solidly to the hard bottom. Usually structures are held in place against wave forces by their own weight or by filling them with rocks. In hurricane regions, where there is a tradeoff between how long it takes to get the structure solidly cemented to the bottom and when the first hurricane hits, we drill holes for vertical rebar supports; a couple of feet is usually adequate. In sand, we anchor reefs using rebar pounded into the substrate.

Where do the corals on a Biorock structure come from?

Our divers never damage an existing, healthy reef to populate a Biorock structure. In all cases, we transplant broken fragments of live coral that have been damaged by waves, storms, anchors or by other means. These pieces would almost certainly die as the fragments roll over in heavy waves and become buried in sand.

How are the corals attached?

Coral fragments are wedged into crevices and holes within the structure or attached using plastic cable ties or steel binding wire.

What happens after the coral fragments are attached?

Within days to weeks, as the mineral accretion grows around the attached coral fragments, corals begin to grow at accelerated rates. Their rapid growth is directly attributable to the electrical current in the underlying steel framework.

Will natural corals settle and grow on Biorock structures?

Coral larvae, which are millimeter-sized freely-swimming baby corals, will only settle and grow on clean limestone rock. This is why conventional artificial reefs made of tires or concrete rarely exhibit hard coral growth.

But, when these coral larvae find a limestone surface, they attach themselves and start to grow skeletons. Mineral accretion is exactly what they are searching for. As a result, there are very high rates of natural coral settlement on Biorock structures.

Are fish and other marine creatures attracted to Biorock reefs?

Like an oasis in the desert, all forms of coral life are quickly attracted to Biorock reefs. Many forms of reef life have been observed to be attracted to the structures, and none repelled.

However it is the organisms with limestone skeletons, such as corals, clams, oysters, barnacles, tube worms and sand-producing algae that are especially benefited, allowing them to outgrow weedy algae that often smothers and kills corals in polluted waters.

The result is that mineral accretion structures quickly become real coral reefs dominated by corals with a wide variety of normal reef creatures.

Why do corals grow faster on a Biorock structure?

Corals grow at accelerated rates with mineral accretion because the electricity flowing through the structure creates chemical conditions (high pH) at the surface of the growing limestone crystals and at the surface of the coral’s limestone skeleton, greatly speeding up their growth.

Corals normally have to spend a large part of their energy to create these conditions in order to grow their skeleton, but mineral accretion provides the right conditions for free, leaving the coral with much more energy for tissue growth, reproduction, and resisting environmental stresses.

Does mineral accretion improve coral health?

Corals attached to a mineral accretion structure are typically more brightly colored and extend their tentacles to feed more often. Because they have more energy for growth and reproduction they are much healthier and are able to survive environmental stresses that would otherwise kill them (excessive temperatures, sedimentation, and pollution).

Have mineral accretion results been documented?

During 1998, when more than 95% of the corals in the natural reefs in the Indian Ocean died, only 20-40% of the corals on the five mineral accretion structures at Ihuru in the Maldives died. The difference of less than 5% survival on the natural reef versus 60-80% survival on mineral accretion reefs was a dramatic demonstration of just how well this process works in a stressed environment.

Do Biorock reefs require maintenance?

Just as a gardener pulls up weeds that would overgrow the flowers, undesirable weedy organisms and certain sponges and algae that could overgrow corals are periodically removed. Organisms that kill corals, such as the crown of thorns starfish and certain coral-eating snails are eliminated.

Biorock reefs also need to be periodically checked to ensure that cables and connections are intact. If these wires are broken, growth of mineral accretion will stop and growth rates of corals will decrease to normal values and lose their special ability to resist adverse conditions. If problems are found with a cable, it is repaired or replaced as needed.

What is the lifespan of a typical Biorock reef?

The longer a project runs, the more corals will grow and be protected from future hot episodes. A project can have its power turned off at any time, but then the special advantages of growth, strength, self-repair, accelerated coral growth and survival will be lost. However, once the structure is sufficiently strong, the power can be reduced to maintenance levels.

Where are Biorock reefs in operation?

Mineral accretion coral reefs are currently being operated in the following countries:

.        Indonesia, Bali

.        Jamaica

.        Maldives, Ihuru and Vabbinfaru

.        Mexico, Yucatan

.        Panama, San Blas Islands

.        Papua New Guinea

.        Saya de Malha

.        Seychelles

.        Thailand, Phuket

Where are the most exciting Biorock projects?

Point, and Nizuc Point National Marine Park in Mexico. In August 1999 the first of two pilot structures was placed in the reef of Sac Bajo, (next to Isla Mujeres, across from Cancun). Shaped like a triangular prism, the reef is approximately 3 meters long and 1.5 meters high. In March 2000 a second structure was placed at the same location, approximately 5 meters away from the first. This structure was named "El Doble Caracol" (twin snail shell), owing to its shape of a double spiral of steel construction mat. This structure is approximately 4 meters long, 3 meters wide and 1.5 meters high.

Barnacle Reef, Ihuru in the Maldives. The Barnacle Reef on Ihuru in the Maldives was built in November 1996. Shaped like a barnacle, the metal structure is roughly 20 feet long by 12 feet high and is submerged in about 20 feet of water. Solar powered. Kimbe Bay, New Britain, Papua New Guinea The pilot nursery project has three parts with a total area of 16.56 square meters, powered by solar panels

Pemuteran Coral Reef Restoration Project. Over forty Biorock coral nurseries have been installed in the Pemuteran Village Marine Protected Area in Northwest Bali, Indonesia with a total length of 300 meters

Kwadule Island, Kuna Yala, Panama . The total length of the structure is 120 feet.

How far off shore can one place a Biorock reef?

Normally we use shore based DC power sources (chargers, solar panels, windmills etc.) Because of voltage drops in the cable to the structure we prefer to work within 100 yards of the power source. But there is no problem going further if one is willing to boost the voltage at the source to compensate for voltage drops. We have a coral reef structure in the Maldives that is more than 400 meters from shore.

How deep beneath the surface of the water can one place a Biorock reef structure?

There is no limit to the depth. Normally we build structures in shallow water (5 to 25 feet bottom depth) because corals grow best in brightly lit shallow water, but we also try to have them deep enough that boats can't run into them.

Why aren’t there more Biorock reefs?

There are many requests for mineral accretion projects from marine conservation groups around the world, but unfortunately there is little funding available from governments, international philanthropic agencies or private foundations.

As a result, most mineral accretion reefs are pilot projects that demonstrate the process. The results are so unexpectedly spectacular that one must see them directly to appreciate their value.

What are some other methods you might suggest to those environmentally conscious people who wish to preserve our coral reefs for our progeny?

It is too late to stop global warming from having severe future impacts so we need to focus on restoring damaged habitats now.