GCRA
OVERVIEW
FAQ
NEWS
ARTICLES
PHOTOS
REEF ISSUES
RESTORATION
PAPERS
LINKS
|
|
|
|
Seychelles
Reef Restoration Project:
Thomas J. Goreau, Ph.D., President, Global
Coral Reef Alliance February 16 2005 Summary A pilot coral nursery project for reef restoration was started in early February 2005 at Sainte Anne Island, Seychelles. It is a joint project between the Seychelles Centre for Marine Research and Technology (SCMRT), the Seychelles Marine Park Authority, (MPA), the Marine Conservation Society of Seychelles (MCSS), the Sainte Anne Resort (SAR), and the Global Coral Reef Alliance (GCRA). The purpose is to save broken coral fragments damaged by the Tsunami, and to demonstrate the potential for large-scale projects to restore Seychelles' damaged coral reefs and fisheries. Introduction: Need for Reef Restoration in Seychelles Coral reefs in Seychelles are badly damaged and in critical need of restoration. The major damage took place in 1998, when around 95% of corals were killed in most Seychelles reefs, with the exception of few turbid sites like the entrance to Victoria Harbour and the Alphonse Lagoon (Goreau 1998a, b, c). While there has been some slow recovery since then, there was further damage from the December 26 2004 Tsunami. Previous Work There have been several previous efforts at reef restoration in Seychelles. In 1997 a restoration project was set up the Sainte Anne dock by MPA and GCRA, using the electrical Biorock method of Hilbertz and Goreau to grow corals on a reef made from confiscated fish traps. The project worked perfectly, with rapid coral growth and fish attracted, but unfortunately a wave ripped out the power line to the dock and it was not repaired, so the project was abandoned. In 1998 a proposal was submitted to the World Bank Global Environment Facility by MCSS to work with GCRA to set up a coral nursery to save corals that survived the 1998 bleaching and which would be damaged by the dredging along eastern Mahe. This project was unfortunately not funded by WB/GEF due to outside political interference. Apparently some efforts were subsequently made to transplant corals from the area, but there is no information on the results. In 2002 MPA and GCRA, using a small private donation to GCRA, started another restoration project at the original site. This consisted of a 12 foot diameter geodesic dome. Unfortunately the structure was not well anchored, and the hollow steel tubes proved too light, and it was damaged in subsequent storms. The 2005 project marks the third effort at this location. Current Work: Project Description The reef structure consists of a mass of twisted steel reinforcing bars that were carried from the garbage dump, towed by boat to the site, and sunk at the base of the slope of the Sainte Anne Jetty, at a depth of around 6 meters. This structure is sufficiently heavy (roughly a quarter metric tonne) that there is virtually no chance of it being moved by waves. Two anodes are placed on either side, weighted down with rocks. A battery charger located in the building at the end of the dock is connected to the anodes and the reef structure by electrical cables sheathed in plastic hoses to prevent chafing on the rocks. These maintain a voltage across the reef and anodes that drives a small direct current through the water between them. This current is completely safe to swimmers and marine organisms. The current causes the pH to be raised at the surface of the steel reef. This prevents any rusting (in fact reversing any that had previously taken place), causing white limestone rock to grow on the steel surfaces, speeding up the healing, growth, and environmental stress resistance of coral fragments placed on it, and attracting fish, shellfish, and other marine organisms. The voltage and current are controlled at a low level by a dimmer switch. The current and voltage were adjusted to 15 amps at approximately 3 volts, so that the power consumption is about 45 watts. Because the charger has an automatic control system to prevent overheating (which is not needed at this low charging rate, but is built into the device) it goes through an on/off cycle of about 10 minutes each. This will slow the growth of the limestone, but will not be damaging, in fact it might even be beneficial. Broken coral fragments from the tsunami rubble on the other side of the dock were transplanted onto the steel reef, being wedged between the bars so they could not move. Current Work: Initial Results Two days later the reef structure turned white as limestone grew on it, being thickest at the ends near the anodes, the corals had healed and looked healthy, and large numbers of juvenile fish had aggregated around the reef. Future Work; Monitoring and Maintenance Due to limited time, divers, and air, we were only able to put around 8-10 pieces of coral on the reef, mostly Acropora, Porites, Pocillopora, Stylophora, and Oxypora. There are many broken coral pieces lying in a wave of rubble on the north side of the dock as the result of the Tsunami, and most of these will eventually die from rolling around. As many as possible should be placed in the reef, wedged in so that they are fixed in place. This will save these corals, and the more corals on the reef the more fish will be attracted, making a unique snorkeling attraction. While many of the ropes that tied the steel to the floats were removed, the longer ones need to be cut off and removed so that they do not wrap around and damage the corals. The charger needs to be checked from time to time, to ensure that it is going through a regular on/off cycle and reads about 15 amperes. As long as the process is working, the reef structure will be giving off small bubbles, and the anodes will be bright and shiny. If the bubbles stop and the anodes become overgrown with fouling organisms, the current supply has been cut off due to a malfunction of the power supply or a broken cable. The cables should be checked for damage after major storms, and rocks placed on them so they do not move. If the anodes are buried in sand they should be exposed. Rocks must be placed on them to keep them from moving and being damaged, but some rocks can also be placed under them to keep them from being buried in the sand. Gloves should be used while working on the anode, as it is much sharper than it looks and can cut the hands if you pull on it barehanded. The project should be photographed from time to time to document the growth of corals and the limestone on the structure ad the number of fish in the vicinity of the reef and photographs sent to GCRA for evaluation and advice. Broken coral fragments similar to those transplanted should be placed on the slope nearby at the same depth as the reef to serve as controls, and should be photographed at the same time to contrast coral survival, growth, and fish populations with those on the reef. Recommendations A paper on the progress of the project should be presented at the Western Indian Ocean Marine Science Association (WIOMSA) Symposium in Mauritius later this year. The project should be closely followed and if it is judged successful, funds should be sought for large scale coral reef and fisheries restoration projects in Seychelles. There is sufficient steel at the junkyard to build very large reefs of this kind. A regional training course in Biorock electrical reef restoration should be held after the WIOMSA Symposium. Acknowledgments SCMRT and MPA provided boats, vehicles, diving gear, and assistance in moving the steel. MCSS provided accommodations. Sainte Anne Resort provided the dimmer switch and electrical power. GCRA and Sun & Sea provided the anodes, electrical power supply, cables, epoxy, and hoses. |
|