Following the mass bleaching event of 1998, the corals in Shark Bay, and Ao Taa Chaa, were almost 100% killed and by 2005 were showing little signs of recovery. To address this problem, the Ao Taa Chaa Biorock was installed in 2005 using funds from the island’s dive schools and the now disbanded Koh Tao Dive Operators Club (KTDOC).
Biorock is an artificial reef structure that uses low voltage electrical current to improve the growing conditions for corals and other reef organisms. This process is called mineral accretion, and uses electrolysis of sea water to lower the surrounding water pH level which causes minerals to precipitate out and collect on the structure by. Corals, calms, and other calcium carbonate secreting organisms growing on the structure are able to grow on an average of 3 to 5 times faster, and in a wider range of environmental conditions, such as warmer, more acidic, or more nutrient rich waters (Goreau 2007; Smith 2002).
The structure of the Biorock (cathode) can be built into almost any shape with a variety of functions to create coral or fish nurseries, restore marginalized areas, control beach erosion, and support the local environment and economy. Structures can be built by community members, private businesses, hotels, or anybody else interested in reef and coastal management. After construction based on the purpose of the structure, all of the features are joined together into one large Biorock structure.
Global Sea Surface Temperatures in 1998 and 2010 were the highest that they have been in over 650,000 years. During years of intense sunlight and warm waters, algae living inside the corals which provide for 85% of their energy is lost, causing the reefs to loose their color and turn white. Some corals are able to recover their algae after temperatures go down, but many will die. This was first seen on Koh Tao in 1998, when a large proportion of the islands reefs bleached and died. During this last year, widespread coral bleaching has been experienced all around the island, with some areas up to 98.1% bleached (Ao Leuk, May 20th, 2010). Already by the beginning of June 2010, 20% mortality of hard corals was seen in areas like Chalok Ban Kao during reef surveys conducted through the Save Koh Tao/SSI Ecological Monitoring Program.
During this time however, rates of bleaching and subsequent mortality have been found to be much lower on the Biorock projects than the surrounding areas. In a survey conducted on the 19th of May 2010, only 10% of the naturally growing hard corals around the Hin Fai site were considered healthy, while over 56% of the hard corals on the Biorock Structure were listed as healthy.
News about the Ao Taa Chaa Biorock Site:
The power supply for the Taa Chaa Biorock (built in 2005) broke over 1 year ago, and has not yet been fixed. The cause for the broken transformer was the electrical supply line and the age of the transformer. In order to get the project running again we will need:
• A new electrical line running from the Government grid to the site location (through OK II Resort)
• A new box installed below a bungalow at OK II Resort to house the transformer
• A new electrical transformer to power the site
• A protective cover (made from PVC) for the site anode
For more information about Biorock Structures, or if you want to use this technology on your reef or coastal area please see:
The Global Coral Reef Alliance