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Asia Dive News : Rebuilding the reefs in Thailand

For years coral reefs have been destroyed by both natural and man-made causes. Realising the importance of coral reefs both as a sanctuary and nursery grounds for all kinds of marine life and as a tourist attraction, several governmental and private sector organisations have initiated coral rehabilitation projects in many areas in the Gulf of Thailand and the Andaman Sea.

However, instead of achieving their goals, some of these activities have unwittingly destroyed the reefs even further.

Studies conducted by the Phuket Marine Biological Centre (PMBC) in the Andaman Sea over the past 12 years found that degraded areas can be restored through coral rehabilitation. However, it is a costly and laborious task, and there's no guarantee that it will be successful in every place because the survival and growth rate of coral depends on various environmental factors, including currents, turbidity, human activity and sedimentation.

One of PMBC's more successful studies involved laying out various configurations of concrete cylinders on ravaged reefs on the eastern side of Maiton, a small island 5km off Phuket. The cylinders were aimed to serve as artificial substrates on which coral larvae could settle and grow.

After six months, new coral colonies had started to settle and now, 12 years later, there are hardly any signs of the cylinders as they are fully covered by coral, comprising mostly of hump coral (Porites lutea) and fire coral (Millepora sp). It was found that the most complex cylinder was the best substrate for coral as it has many crevices that can better protect coral larvae from predators and sedimentation. Fish and other marine life that disappeared when the reefs were destroyed by a storm in 1986 have also returned.

One quarter of all marine fish species, as well as crustaceans, shellfish and other marine animals, either live or spend the early parts of their lives in coral reefs, and the fact that they are back serves as testimony to the health of the restored marine ecosystem. At Maiton Island the water is so clear and clean that on a sunny day snorkellers can see squid and giant clams, sea anemones and soft coral, in addition to various species of colourful fish, even though there's a resort on the island.

During the course of their study, the researchers found that following a storm, the sandy bottom of the sea becomes strewn with coral debris which is easily moved or abraded by strong waves, thus inhibiting the successful growth of larvae.

The environment also has a role to play in the recovery of damaged reefs. If the substrates, both artificial and natural, are in an area of high sedimentation, strong waves or water turbulence, the larvae cannot settle down. Even if they do, survival rates will be low. Sediment and abrasion are the main causes of post-settlement mortality of coral larvae, the researchers found.

Armed with this discovery, and prompted by the success of the Maiton coral rehabilitation programme, the PMBC expanded its work at the island last year as part of an international cooperative effort to restore coral reefs in the Indo-Pacific region. This is a four-year programme called "Developing Ubiquitous Practices for Restoration of Indo-Pacific Reefs", or Reefres, and was started with the participation of seven organisations from six countries _ the UK, Italy, the Philippines, Singapore, Israel and Thailand _ with financial support from the European Commission.

The new project at Maiton is aimed at finding proper substrates that will further enhance the number of new coral settlers and their early survival rate, and improving techniques and effectiveness of coral rehabilitation. This time around, only the most complex concrete cylinders, with different degrees of surface roughness, were laid at the bottom of the sea.

Six months after the project started, new coral colonies which settled on the cylinders began to be visible to the naked eye. It is expected that as with the previous project, the provided substrates will help increase the number of coral colonies in the waters around the island.

Another PMBC research as part of the project is a study of the suitable size of hump coral for transplantation. Different fragment sizes of hump coral were attached to concrete blocks using quick-drying cement, and placed at the same depths near the reef where the coral was taken from. The survival and growth rates of the fragments are now being monitored, to determine the size that is best suited for coral rehabilitation programmes in areas where reefs have been ravaged by natural or man-made causes.

Under the Reefres project, researchers from Israel's National Institute of Oceanography are conducting experiments, with assistance from PMBC staffers, to see whether their experience in coral rehabilitation in the Red Sea could be applied in the Andaman Sea. The work involves taking "nubbins", or tiny fragments of coral, and growing these in nurseries suspended in water until they are big and strong enough for transplantation to tsunami-affected areas.

By using tiny fragments, the pressure on donor corals is reduced, while the floating nursery reduces the threat from coral-grazing animals and sedimentation, thus improving the coral fragments' chances for survival.

The floating nurseries are located near the PMBC pier at Cape Panwa and at Koh Hae, a small island 3km away. Four species of coral _ Velvet stone coral (Montipora aequituberculata), plate and pillar coral (Porites rus), staghorn coral (Acropora formosa), and cauliflower coral (Pocillopora damicornis) were cut into about 0.5 to 1.0cm nubbins and attached to a plastic pump hose and then put in the nurseries, where the fragments were raised.

Last April the first crop of coral was big and strong enough to be transplanted to Koh Phai, a small island in Krabi where the coral reefs were devastated by the 2004 tsunami.

Applying the knowledge gained from the Israeli scientists, the PMBC has since set up another floating nursery at Phi Phi Ley, which is now serving as the temporary home for 1,100 coral fragments. The PMBC researchers are helped by members of diving companies on the island, who will be transplanting the coral fragments next month.

At the end of this month, from September 30 to October 4, scientists taking part in the Reefres project will have their annual meeting to share and exchange knowledge, ideas and experiences. As hosts for the meeting, the PMBC is taking the opportunity to share the knowledge and experience its researchers have gained from their own studies, as well as from the international cooperative programme, with Thai government officers, academics and others who work in the same field.

Scientists participating in the Reefres meeting will serve as guest lecturers and talk on subjects ranging from ecological approaches for the restoration of damaged reef habitats, the scale of the problem and the status and prospects for restoration technologies, coral transplantation in the Red Sea and coral restoration experiences of researchers working in the Philippines, Singapore and Thailand.

The scientists will also talk about coral reproduction through sexual and asexual means, and restoration work after the tsunami. Following a field trip to see the floating coral nursery at Koh Hae and the coral rehabilitation site at Maiton, the last day of the meeting will be a brainstorming session by Thai participants on criteria to be followed in the restoration of coral reefs in Thai waters.

However, despite a wealth of academic knowledge, we still face difficulties winning over nature, as the restoration of coral reefs depends on optimal environmental conditions _ clear, unpolluted water, a stable substrate, salinity of between 28 and 34psu (practical salinity unit), water temperature between 26 and 30C and no disturbance by human activity.

If a suitable environment can't be found, all the knowledge we have gained will be useless.

Dr Nalinee Thongtham is a marine biologist at the PMBC and heads the coral rehabilitation project at Maiton Island and the PMBC's Reefres Project. For more information about coral rehabilitation or the Reefres meeting, call 076-391128, 084-0539760 or fax 076-391127.

Source: Bangkok Post

 
 
 
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