From hendee@aoml.noaa.gov Fri Sep 4 07:48:41 1998 Date: Wed, 1 Jul 1998 15:54:42 -0400 (EDT) From: Jim Hendee To: coral@aoml.noaa.gov Subject: Coral bleaching Thailand (fwd) ---------- Forwarded message ---------- Date: Wed, 01 Jul 1998 18:57:13 +0200 From: Ed Colijn To: coral-list@coral.aoml.noaa.gov Subject: Coral bleaching Thailand Bangkok Post [Two Articles] June 29, 1998 Worst ever coral bleaching in Thai seas Sea temperature rise puts coral at risk Kanittha Inchukul The warming of sea water has caused widespread coral bleaching in the Gulf of Thailand from Trat province in the eastern coast down to Singapore, according to Chulalongkorn University's marine science expert Suraphol Sudara. He described the phenomenon as the worst ever to occur but stopped short of putting the blame on El Nino. Dr Suraphol said coral bleaching was detected in April in almost every part of the gulf especially tourist attractions such as Chang, Tao and Pha-ngan islands. Fortunately however, he said this had not yet occurred in the Andaman Sea. Coincidentally, he noted that the same phenomenon was also detected in the Great Barrier Reefs in Australia and in Singaporean waters. He disclosed that the temperature of water in the gulf had increased significantly from an average of 28-29 degrees Celsius to 32 degrees. He said it could be possible that the warming of the sea water was caused by the El Nino weather phenomenon. The bleaching is caused by the escape of a kind of algae called zooxanthellae from the coral structure as a result of sea water warming. Eventually, this can lead to the death of the coral. Also affected by sea water warming is giant clam or hoi mue sua. Dr Suraphol said it was as yet too soon to predict whether the affected corals would survive or not. Normally, he said it would take at least 2-3 years for the bleached corals to start to recover slowly unless the problem is further compounded by sea pollution. The immediate impact of coral bleaching is a drop in the number of tourists who are interested in diving or snorkelling with the long-term impacts yet to be determined, said the scientist, adding that the death of corals would result in more serious shore erosion as corals serve as a natural barrier to waves. Dr Suraphol's concern about coral bleaching confirms the alarm raised by some diving instructors who earlier observed the phenomenon in the sea off Pattaya, near Samaesan and Koh Samet island. Dave Chandler, in his letter to the Bangkok Post, said he suspected sea water warming as the culprit but did not rule out pollution from industrial sites and discharges from tankers and vessels. The Pattaya-based diving instructor said both soft and hard corals had died, leaving only bleached white limestone. Nevertheless, he said other corals look healthy and unaffected. Mr Chandler said his diving computer measured sea temperature at 33 degrees Celsius in shallow water and 32 degrees at depths below 6-8 metres. Normally, the temperature would be no more than 30 degrees, he noted. He expressed concern that if the corals were wiped out, it would deal a tremendous blow to the ecology of the gulf and would seriously threaten Thailand's badly-needed income from tourists who come here to dive. =================================================== More than a little off colour MARINE LIFE: Scientists have discovered many of Thailand's coral reefs are not looking very healthy. In some places 100 percent of the most common Acropora coral has been bleached white Dr Suraphol Sudara and Dr Thammasak Yeemin of the Coral and Seagrass Research Unit, Chulalongkorn University A healthy coral reef is a dynamic world of vivid colour thanks to the single-cell algae called zooxanthellae. This algae, which lives in the cells of the coral, shares a symbiotic - or mutually advantageous - relationship with the coral. The zooxanthellae provides the coral not just with colour, but also extra food through the process of photosynthesis. In return, the coral gives the algae a home and protection inside its skeletal structure. Things normally go well between the two partners until something disrupts their symbiotic relationship, resulting in the coral host kicking out its algal roommate. The sad fact is in most cases, coral cannot survive on its own - without zooxanthellae it bleaches white and gradually dies. The even sadder fact is, this is happening now in the Gulf of Thailand. Since the 1980s marine biologists around the world have been concerned about coral bleaching, and although they could see it happening in many places, scientists were having a hard time confirming what was actually causing this disastrous phenomenon. Even today, there is no conclusive evidence about why bleaching actually happens. Coral bleaching has occurred in the Caribbean, the Pacific and Indian Oceans, and in the Arabian Gulf and Red Sea. Bleaching was first noticed in Thai waters in 1979 on a few patches of coral off Phuket. By 1991 the problem was widely recognised on the Andaman side of the kingdom. It was not really observed in the Gulf of Thailand until recently. Then in late April, the bleaching of coral in the Gulf was widely noticed at islands off the coast of Chumpon and Surat Thani. Then it was discovered areas on the east coast such as Rayong, Trat and the inner part of the Gulf around Ko Sichang and Pattaya were also affected. But the phenomenon was quite strange. While some species in the coral colonies were affected by bleaching, others were maintaining their normal colour. A preliminary survey at Ko Rum Ra offshore from Bangsapan, Prachuab Kiri khan province, where bleaching was noticed at the end of April is continuing to this day. The situation there seems serious as the reef appears in parts to be completely white. About 10 species of the Acropora group - which includes staghorn coral and table coral - had suffered almost 100 percent bleaching; Pocillopora damicornis is about 80 percent bleached and the other 20 percent is pale in colour; about 60-70 percent of massive coral in the Porites group were found to be bleached, especially the coral lying in shallow flat parts of the reef. Coral in the shallower water appears to have been more effected by the bleaching than that in deeper water, and the sea water temperature in shallower areas was found to be rather high, around 32-33 degrees Celsius. The reefs around Koh Tao, a popular island for divers and snorkelers has also fallen victim to bleaching which was observed there in early May, when the recorded sea water temperature also proved to be high - about 31-32 degrees Celsius. The most significant impact appears to be on the Acropora group of hard corals - the most commonly found coral in this region - which was completely bleached white. More than 80 percent of another hard coral Pocillopa damicornis was found to be bleached. Fungia were also all found to be bleached and even some species of colourful soft coral had turned white. It appears the bleached soft coral might not be able recover. Similar bleaching incidents were recognised at coral communities on the inner part of the Gulf starting from Ko Sichang through to Pattaya to Sathaheep. A survey also showed bleaching extended further along the east coast of the Gulf of Thailand to Trat. The extent of the bleaching and the long-term damage it causes to the reef remains to be seen. The death of particular species - particularly the Acropora group - appears to be extensive. While it might be possible for the coral to recover from the effects of bleaching, the problems it faces do not end there. If the coral is overrun by filamentous algae, or if other alien invertibrates make their homes on its skeleton, rejuvenation of the coral might be hampered or indeed made impossible. Some groups of coral might recover, such as Galaxea, Platygyra and Lobophyllia, but the question of how long the recovery process could take remains a mystery. As is understanding how great the impact will be on the reproductive cycle or fecundity of the effected reef organisms. Neither is it known what the long term impact of bleaching will be on other reef organisms such as sea urchins and reef fish. Or whether the bleaching will increase the rates of bio-erosion on the reef. All these issues still need to be studied. The cause of the unusually high sea water temperatures all over the Gulf of Thailand remains to be proved by physical oceanographers, however it has been suggested it is linked to the El Nino weather phenomenon. Even though El Nino is more or less over, this bleaching might be part of its legacy. © Copyright The Post Publishing Public Co., Ltd. 1998 -- Ed Colijn edcolijn@bart.nl The Indonesian Nature Conservation Database http://www.bart.nl/~edcolijn/