The St Andrews Prize for the Environment

University of St Andrews


2005 Finalist

Global Coral Reef Alliance

Global Coral Reef Alliance

Growing, protecting and managing the most threatened of all marine ecosystems

The Global Coral Reef Alliance is a non-profit organisation dedicated to growing, protecting and managing the most threatened of all marine ecosystems, namely coral reefs. Through extensive research, GCRA has pioneered methodologies to help reefs survive and recover from diseases and anthropogenic damage caused by excessive nutrients, climate change and physical destruction.

A low voltage electrical current applied to a submerged conductive structure causes dissolved mineral crystals in seawater to precipitate and stick to it. 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.

Biorock™ structures can be built in any shape or size depending on the physical make-up of the sea bottom, wave and current energies and construction materials. They are well suited for remote, third world sites where exotic building materials, construction equipment and highly skilled labour are not available.

GCRA methods provide a cost effective way to increase coral survival from bleaching and disease, and restoring damaged reefs. In time these structures cement themselves to the ocean bottom, providing a physical barrier that can protect coastlines from waves and currents that cause erosion.

In the Maldives, during the 1998 warming, fewer than 5% of the natural reef corals survived. But on GCRA reefs, 80% of corals survived, and flourished. Corals from these reefs are now re-colonising the natural surrounding habitats.

To build a Biorock™ reef, an electrically conductive frame, often made from construction grade rebar or wire mesh, is welded together, submerged, and anchored to the sea bottom. Sizes and configurations vary to fit the setting. The power is applied using an anode from sources including 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.

Within days, the structure takes on a whitish hue as it becomes encrusted with precipitated minerals adding rigidity and strength. Electrical fields, plus the shade and protection offered by the metal/limestone frame, attract a wide range of colonising marine life including fish, crabs, clams, octopus, lobster and sea urchins.

Once the reef structure is in place, divers transplant coral fragments from other reefs and attach them to the frame. Immediately, these coral pieces begin to bond to the accreted mineral substrate and start to grow – typically three to five times faster than normal. Soon the reef takes on the appearance and utility of a natural reef ecosystem rather than a man made one.

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