Coral reef transplanting/restoration technologies

Needs Address

The need to reduce the loss and bleaching of coral reefs in areas where they may be affected by sea surface temperature rise, by increased CO2 concentrations in seawater, and by increased intensity of tropical cyclones, and where the loss or bleaching of coral reefs due to human disruptions can already be observed.

Adaptation effects

• Prevention of deterioration of natural ecosystems due to rising sea surface temperatures, rising CO2 concentrations, and increased intensity of tropical cyclones due to climate change
• Prevention of flood damage caused by extreme events
• Disaster prevention, coastal erosion prevention, supply of sand

Overview and Features

・Coral transplantation technologies are in the following two major categories.
   √ Asexual reproduction: Coral fragments are gathered from natural waters, transplanted fragments are propagated on cultivation substrates, then secured underwater at target sites using bonding materials, etc.
   √ Sexual reproduction: Eggs and larvae are gathered by various means, and then cultivated polyps are transplanted to target sites in the sea.
・ Transplantation by asexual reproduction is easier technology to apply than sexual reproduction, but it comes with various problems. For example, if it is a population from limited fragments, even if spawning occurs, fertilization does not succeed due to the lack of genetic diversity, so descendants do not survive. Also, the act of taking transplantation fragments from existing coral reefs damages them. Below is an introduction to the sexual reproduction transplantation method, which has progressed somewhat through research in recent years.

Spawning Coral

・ The key steps in transplanting by sexual reproduction are as follows:
   √ The spawning date is predicted and fertilized eggs are obtained. (In some cases eggs and sperm are collected directly, and fertilization is done artificially by hand, then the larvae are raised.)
   √ Planula larvae are grown in cages floating in the sea or in indoor aquariums.
   √ Planula larvae are attached to substrates to which calcareous algae  have been attached, and juvenile coral are created in baskets in seawater.
   √ Larvae are raised to create populations.

→ If only small numbers of larvae are attached to the substrate, they can be covered by surrounding sea grass and die, so the common practice is to raise them together with button shells (Tectus niloticus), which eat sea grass but not coral.

Source: http://www.amsl.or.jp/body22.html

   √ Corals that have grown to 5 to 10 cm are transplanted in seawater by hand by divers.

Important points about coral transplantation and restoration technologies: Scientists differ in opinion about the effectiveness of transplantation and restoration technologies. Some of these points are that artificial transplantation can only succeed in limited areas compared to the area of damaged coral reefs, and that the technology itself is still new and needs to be proven and improved in each marine area. It is important to continue making and adopting improvements to methodologies and adapting them to natural and social characteristics in each marine area.

Cost

・$27,616 per year
Note: Annual cost estimate for 10,000 branches of coral fragments in a restoration project using modular trays on location where they can be raised.

Source: Reef Rehabilitation Manual (Coral Reef Initiatives for the Pacific, 2010)

Considerations

・Cost is expensive.
・Raising planula larvae and juvenile coral is labor-intensive/time-consuming. (This means that for technology transfer to succeed, it is important to explain the need for technology transfer and transplantation, and careful effort is required for capacity building and management methods among managers at the local level).
・After transplantation, comprehensive studies and research are required, monitoring in particular.
・Awareness-raising activities and economic incentives are needed at the local level.

Co-benefit, suitability for developing countries

・ Conservation of biodiversity (the area contains diverse habitat for flora and fauna in coastal zones)
・ Prevention of soil erosion due to storm surges.
・ Supply of sand to beaches.
・ Diversity of fish and other fisheries resources can sustain and stimulate the fishing industry.

Information Resources

・"Current status and issues of artificial coral transplantation," Reef Conservation Committee, Japanese Coral Reef Society, Journal of the Japanese Coral Reef Society, Vol. 10, 73 – 84, 2008 (in Japanese).
・"Okinawa Prefecture Coral Reef Transplantation Manual," Nature Conservation Division, Department of Cultural & Environmental Affairs, Okinawa Prefectural Government, 2008 (in Japanese).
・ Akajima Marine Science Laboratory website
http://www.amsl.or.jp/eng/index.html
・ "Reef Rehabilitation Manual" (Coral Reef Initiatives for the Pacific, 2010)