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Caqalai Island Hub Achievement Report March 2015 Objective: Reef Regeneration

Caqalai Biorck Project Biorock is an artificial, revolutionary process designed to help speed up coral regeneration. The process enhances the growth of coral aggregation using electrolysis.

Figure 1 - An example of a successful biorock structure

Background

Biorock technology was discovered in the early 1990s by an American scientist called Wolf Hibertz. The process uses either AC or DC electric current, which is conducted through a steel rebar structure. Coral fragments are secured to the electrified structure and a second electrified structure of lower nobility, usually titanium or aluminum is placed nearby. The positive output from the power source is connected to the sacrificial anode, or the metal of lower nobility, which then corrodes releasing H+ ions and creating an ion field. This ion field engulfs the cathode, which is connected to the negative output causing a reaction that releases OH- ions, increasing the pH around the cathode. This causes calcium carbonate to precipitate out from the surrounding water column. By providing coral with abundant

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calcium carbonate, the key building block for coral growth, the coral expends less energy on calcium carbonate production and therefore has more energy available for growth.

The optimum voltage directed through the structure is 6V. If the voltage is too high magnesium carbonate forms which does not solidify, if it is too low no calcium carbonate will form. Immediately after the circuit is created from the ion field, small trails of bubbles are seen coming from both the anode and the cathode. The following reaction is occurring:

At the cathode - 4H2O + 4e- 2H2 + 4OH-

At the anode - 2H2O O2 + 4H+ +4e-

The bubbles are Hydrogen being released from the cathode and oxygen being released from the anode, the OH- ions at the cathode continue in a secondary reaction to form CaCO3:

Ca++ + HCO3- + OH- CaCO3 + H2O

Biorock has been used across the coral triangle and also areas such as the Red Sea and the Caribbean to promote coastal protection, increased tourism value and reef regeneration. In Pemueteran, Indonesia, the government funded a bio rock structure program starting in 2000 which now has over 200 structures that covered over 2 hectares of coastline. The project was successful and an increase in fish abundance in the region has been linked with the project.

Aims and Objectives

The aim of the Caqalai Biorock project is to design, fund and create a biorock structure using electricity from renewable energy to help enhance the regrowth of up to a 100 fragments of coral. The ultimate objective of the project is to enhance the growth and durability of cyclone and coral disease damaged coral along the Caqalai Island house reef through an innovative approach to coral planting. If successful, this process could provide an effective way to enhance reef health and resilience. By up-scaling the bio rock process, the method could provide an effective way to create new habitats for commercially important fish while also helping to reduce erosion by acting as a natural barrier.

Methodology

The structure in place at Caqalai base consists of two solar panels, one 140 W and one 50 W, which are connected in parallel and run electricity down two, 60 meter cables. One cable runs from the positive output to the anode, which in this case is a sanded down aluminum scuba tank and the negative output to the cathode, a 6 X 4 m steel rebar structure. Attached to the steel cathode are over 80 fragments of coral from 12 different species using steel binding wire. The panel wattage and wiring has been installed in a way that ensures the voltage delivered to the structure does not exceed the ideal voltage while also ensuring that in most day time conditions the minimum voltage required for the process is met for a significant portion of daylight hours.

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By measuring the growth rates of ten different species of coral on the electrified structure and comparing the rates to coral secured on a non-electrified structure the project will assess the measurable benefits of the biorock process by comparing growth rate benefits against the relative cost of the system.

All coral fragments are taken from within the same area and at the same depth. Along with general monitoring, the structures will require cleaning of any epiphytes which have taken advantage of the more beneficial conditions of the structure.

Once data on growth rate benefits is compared against cost to evaluate the value and scalability of the project there will be opportunities to assess new ways to use the technology to assist the recovery of Caqalais reefs from the devastation caused by cyclone Evan in 2012. There is also potential, based on the current success of the system to trial a more expensive and complex solar powered system using battery banks and solar controllers in order to deliver optimum voltage 24 hours a day.

GVI hopes to trial further innovative methodologies to promote both natural resource recovering and resilience and livelihood adaptation strategies in the area. Though the biorock project is a small scale trial, GVI hopes to share results with relevant stakeholders in an effort to further communicate the effectiveness, value, and accessibility of community run reef health enhancing projects.

Figure 2 - Caqalai Biorock structure

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