Gulf Of Thailand

Marine Biology
Shantal Ortega
1st

The Gulf of Thailand

Introduction
The Gulf of Thailand is a semi-enclosed tropical sea located in the South China Sea, it is surrounded by Malaysia, Thailand, Cambodia and Vietnam. The Gulf covers roughly 320,000 km². The boundary of the Gulf is defined by the line from Cape Camau in southern Vietnam, south of the mouth of the Mekong River to the coastal city of Kota Bharu on the east coast of West Malaysia. It is particularly shallow; the mean depth is 45 m, and the maximum depth is only 80 m. The water temperature in November was 84 degrees Fahrenheit, or 29 degrees Celsius. The water in the gulf is warm year round. The gulf has some of the best diving because of the clear water. The average sea temperature is 28 degrees Celsius. The general shape of the Gulf’s bottom topography is considered elliptic parabolic. It is separated from the South China Sea by two ridges that limit water exchanges to the open South China Sea. The first ridge extends southeast from Cape Camou for about 60 nautical miles with an average sill depth of less than 25 m. The second ridge, which extends off Kota Bharu for approximately 90 nautical miles, has an average sill depth of 50 m. There is a narrow, deeper channel between the two ridges with the observed depth of 67 m. The Gulf can be divided into two portions, Upper Gulf and Lower Gulf. The Upper Gulf at the innermost area has an inverted U-shape. The Upper Gulf is known as the catchment basin of four large rivers on the northern side and two on the western coast.
1. FEATURES OF THE GULF OF THAILAND Some of the physical and chemical features of the Gulf of Thailand include coral reefs, mineral resources and water quality. Coral reefs are havens, or safe places for many species and organisms. They are sensitive to pollution and are under threat from certain fishing practices. The main factors to coral destruction are the setting up of industrial parks and city expansion activities in the coastal areas. Petroleum hydrocarbon production was 957 million cubic feet of natural gas per day as recorded for the first quarter of 1997 by Unocal Thailand. 33,425 barrels of condensate Unocal has drilled over 1,000 wells and has 74 platforms under operation. The total length of underground sea pipeline is now over 1200 kilometers. Natural gas from the gulf supplies about 30 percent of the energy needs of Thailand, and at least 1,000 million cubic feet of natural gas is extracted from new fields per day. Water quality is fair along coastal areas and tourist beaches, except some locations at the mouth of Thailand’s five major rivers; the Chao Phraya River, Lesser Gulf River, Mekong River, Salawin River, and the Andaman River.

2. DEGRADATION OF THE GULF OF THAILAND COASTAL ECOSYSTEM
2.1 MANGROVES
Primary productivity in the gulf is boosted by increased nutrients from rivers, shrimp farms and household sewage. Many cities have no sewage treatment and discharge directly into the gulf. More fertilizers are being used on agricultural lands, which eventually reach the gulf and contribute to the deterioration of water quality. Increases of nitrate, phosphate and silicate are causing harmful algal blooms, red tied, and oxygen depletion. Mercury is also responsible for pollution in the gulf. The Gulf of Thailand formerly supported extensive mangroves. Because of pollution and overfishing, as well as other factors the outcome is clear. These Mangroves are tree shrubs that grow in mainly tropical coastal swamps that are flooded at high tide. The delicate environment is an important source of vital nutrients for several organisms and are only found only on tropical coastlines. Though the mangroves are very important to the gulf, the largest areas have since been cleared for aquaculture and salt pans, only secondary mangrove still remains and is usually found as a narrow (10-l00 m) along the seaward margins. Extensive areas of low scrub are found in the brackish marshes along the landward edge. In places, the open shrimp ponds and salt pans extend two to three km inland and, together with the offshore mudflats, provide an important feeding and roosting area for many thousands of shorebirds. The Mangrove areas are also important fish breeding and nursery grounds, where many species reproduce. There are barriers on the major rivers in and near the gulf, such as dams, weirs, and hydropower structures, which have a major impact on migratory species that swim upriver to spawn. Mangrove destruction is the very clear, and the mangrove has seen the greatest loss. Mangroves are especially sensitive to climate change, the mangrove degradation is becoming alarmingly high. This is due to Thailand 's rapidly developing economy, since the 60 's, the mangrove forests have been reduced by nearly 80%. Shrimp farms, hotels, growing cities and other coastal developments have taken the place of the mangroves. Mangroves are still being cut down for agriculture, coastal construction and aquaculture, but at a significantly slower pace and lower rate.
2.2 CORAL REEFS
Coral reefs are under huge amounts of stress in many areas in the Gulf, especially those near shallow ridges and dense populations. Storms and monsoon waves are the major natural causes of coral reef damage. Typhoon Gay hit southern Thailand in 1989 and caused severe damage to several reefs. Extreme low tides and coral bleaching, this is when corals are exposed to stress such as the changing conditions in the Gulf, these include temperature changes, light and nutrient changes, this causes the coral to expel the symbiotic algae living in their tissues which causes them to turn completely white. Erosion is another natural phenomena causing severe damage. This erosion has been caused by logging, and has killed coral reefs by increasing the turbidity of coastal waters, in a way that the coral polyps no longer have enough light to photosynthesize metabolites and are even be buried by increased sedimentation. Out of over 60% of all major reef groups in the Gulf of Thailand these coral beds will have less than 50% live coral coverage and there is increased algal growth because of pollution to the nutrients from the land, including near the major tourist resorts. Some of the other disturbances on the coral reefs in the Gulf are boat grounding, the destructive fishing methods such as bottom-trawlers and dynamite fishing. This detriment is long term because of the time that it takes the coral to recover.
2.3 SEAGRASS BEDS
One of the least studied marine habitats in the Gulf of Thailand compared to Coral Reefs and Mangroves are the Sea grass beds. Abundant more in the Andaman Sea than in the Gulf of Thailand, no extensive evaluation on the sea grass cover in the country has been studied as of today. The species of sea grass such as Enhalus acoroides, Halodule pinifolia, and Halophila ovalis were reported in the Gulf of Thailand. Only a survey of sea grass around the Samui Island found that the sea grass beds were degraded only in areas where there was considerable industrial construction, shrimp farming and land development. It is obvious that economic activities is the main factor affecting sea grass beds.

3. OVERFISHING IN THE GULF
The Gulf of Thailand is the most productive area of the South China Sea. Thai people being dependent on the fisheries cause overfishing, and exploitation of many important marine life in the gulf. Due to increasing population, exportation in the 70 's and 80 's, we see a fast growing increase in marine fishery production in the country. In the Gulf of Thailand, most of the fish are fully exploited except for Indian mackerel. Almost all stocks are also overfished including fish, shrimp, squid, cuttlefish, and others. Overfishing of the inshore and coastal waters has also been reported in many technical publications. Most of the fish production was mainly "trash" fish resulting from an over excessive fishing effort, capture of undersize fish as well as the all too destructive "push net", which was used as the main fishing gear in the area. Due to overfishing and the resulting decreased availability of fish, subsistence and artisanal fishermen are often forced into destructive fishing techniques such as blast fishing and poisons. The use of these fishing techniques has resulted in lasting deleterious impact to the marine environment in the Gulf of Thailand, especially to its’ coral reefs. An increase in trawl fishermen led to overfishing and caused market failure because the price went down. Oil crisis in 1973 increased cost in fuel, which in turn affected the fishing in the gulf. Things began to take a little turn and in 1993 marine fishery landings were:
Cambodia – 33,100 tons\
Malaysia – 1,047,350 tons,
Thailand – 2,752,486 tons
Vietnam – 824,800 tons.
Human interference on the Gulf of Thailand are islands, populations, shipping, and tourism. The 16 islands that surround the Gulf of Thailand include Pattaya, which is the most famous, Cha am, Koh S amet, Joh Samui, Dranbun, Rayon g, Koh Chang, Koh Kood, Hua Hin, Chumphon, Prachuuap Khiri, Suratthani, Khan, Khon Phangan, Kou Tao, and Koh Nangyuan. Population is also a big interference. In 1996, the populations of bordering nations were as followed;
Cambodia – 10,861,218
Malaysia – 19,962,893
Thailand – 58,851,357
Vietnam – 73,976,973
Population in 2014 is as follows:
Cambodia - 15,135,169
Malaysia – 30,644,293
Thailand – 67,222,972
Vietnam – 92,547,959
This is a significant change for the gulf and as the studies show, directly responsible for the changes in the Gulf of Thailand.

3. THE GULF AND ITS WATER POLLUTION
Pollution has considerably damaged the Gulf of Thailand and its and marine environment. Coastal and marine water pollution in Thailand is mainly due to the direct discharges from rivers, surface runoff and drainage from port areas, domestic and industrial effluent discharges throughout falls and various contaminants from ships. Maps of the urban centers in Thailand are located on coasts and estuaries and thus most of the populations’ wastes and garbage is dumped directly into the shallow areas of the Gulf of Thailand. Because of this, rivers are generally heavily contaminated with the populations’ raw sewage, and industrial sediments. Though this seems terrible, the primary source of marine pollution are the offshore oil and gas drilling, wastes from the shipping industry and transportation, and the all too popular oil spills. Land based pollution include tourism areas, industrial and domestic pollutions. Which are high for the beach resorts and tourism areas, this is especially high with industrial development and aquaculture activities. According to studies, land-based sources contribute some 70% of the pollution, mostly from domestic sources. An estimated volume of more than 200,000 tons of waste is released into the Gulf each year. The quality of the water in the Gulf of Thailand is deteriorating at a steady rate due to increasing runoff of nutrients (to the gulf it is a pollutant) from the increased use of fertilizers in agriculture, the shipping and fishing industry and from household sewage.

4. SCIENTISTS TO THE RESCUE
Although there is growing awareness and concern from the public, the Gulf of Thailand and other Aquatic ecosystems are still degraded by pollution and misuse of the ecosystem. For decades, scientists have been monitoring activities and conducting research in the Gulf of Thailand. Although these activities were typically studied for a specific need, and they were limited in coverage, they failed to give us a full picture of the Gulf 's condition. Though most the general public is not aware of the potential value of marine science to society, several measures have been taken to protect and conserve the marine resources in the Gulf. Since 1972, laws have been put in place to protect the Gulfs ecosystem one of which is that travelers are prohibited from an area within 3 km from the shoreline, and within a perimeter of 400 m of any stationary fishing gear. Also to protect the Gulf, in 1984, an area of about 26,400 km2 in the Gulf was declared as a conservation area, prohibiting any and all fishing, this included during spawning season. Though not in this paper, another regulation was put in place to provide protection of any and all endangered and threatened species, these regulations being the following: prohibition of the catching of sea turtles, the collection of their eggs and the export of sea turtle shells, Catching of dugongs and collection of corals are also prohibited. The Department of Fisheries has also implemented and promotes artificial reef projects to create protected habitats for marine life. Though this sounds good on paper is has sadly failed to be effectively enforced. Scientists continue to study and advocate for The Gulf of Thailand as well as many other Gulfs and coastal waters to help preserve and protect our marine life.

References:
The physical oceanography of the Gulf of Thailand, NAGA(Robinson, 1974) The use of Landsat-5 (TM) satellite images for tracing the changes of mangrove forest areas of Thailand. (Charuppat, T. Charuppat, J., 1997) Overview of shrimp farming and mangrove loss in Thailand. (Aksornkoae, S., Tokrisna. R., 2004)
Shrimp farming and mangrove loss in Thailand. ( Edward Elgar)
Health of fringing reefs of Asia through a decade of change: a case history from Phuket Island, Thailand. (Chansang, H., Phongsuwan, N., 1993.)
The Fishing Status of Thailand. (Chullasorn, S., Chotiyaputta, C., 1997)

References: The physical oceanography of the Gulf of Thailand, NAGA(Robinson, 1974) The use of Landsat-5 (TM) satellite images for tracing the changes of mangrove forest areas of Thailand. (Charuppat, T. Charuppat, J., 1997) Overview of shrimp farming and mangrove loss in Thailand. (Aksornkoae, S., Tokrisna. R., 2004) Shrimp farming and mangrove loss in Thailand. ( Edward Elgar) Health of fringing reefs of Asia through a decade of change: a case history from Phuket Island, Thailand. (Chansang, H., Phongsuwan, N., 1993.) The Fishing Status of Thailand. (Chullasorn, S., Chotiyaputta, C., 1997)