Straits of Malacca and South China Sea are vulnerable to oil pollution because of the huge amount of crude oil transported through these waters annually. The present level of oil pollution in these waters is between 150-300 μ g L− 1 in water and 70–100 mg kg− 1 in sediment. Whenever there is an oil spill in the Straits of Malacca, the level of oil in water could be raised to higher than 500 μ g L− 1. Crude oil, especially the aromatic hydrocarbon fraction, is highly toxic to marine organisms. The index of oil pollution for marine environments is set at 1000 μ g L− 1 oil in water and 100 mg kg− 1 oil in sediment. The non-effect level of oil on organisms is about 50 μ g L− 1 in the tropical sea. Toxicological studies demonstrated that the present level of oil pollution in seawater has some chronic effects on the growth and hatching rate of marine organisms. Thus, technologies are being actively pursued and developed for reducing the oil contamination in water to lower than 50 μ g L− 1 to protect marine organisms. This paper will review the status of hydrocarbon pollution in the Malaysian seas and the impacts on Malaysian marine environments, as well as the techniques used to combat oil spills, and the management strategies in place to secure environmental safety in Malaysia.
Malaysia is surrounded by seas comprising of Straits of Malacca, South China Sea and Sulu Sea. Malacca Strait is the busiest strait in the world for oil tankers. More than 15% of the world trade vessels sail through the strait from the Indian Ocean to Pacific Ocean annually (Harstad, 2002). The number of vessel passing through the strait is increasing from 44,000 per year in the 1980s to over 100,000 in the late 1990s (Naidu, 1997; Chua et al., 2000). More than 30% of vessels using the strait are oil tankers that carry about 3.2 million barrels of crude oil (Chua et al., 2000). The Straits of Malacca is a very shallow and narrow strait with a length of 1100 kilometers (km). The widest section of the Strait is about 400 km in the northwest entrance, narrowing gradually towards the southeast portion with a width of about 15 km. The congested maritime traffic in this narrow strait is prone to tanker collision and the coastal environment is then exposed to the risk of oil pollution. Figure 1 shows the number of oil spills incidents recorded in Malaysian water from 1976–2000, while Table 1 lists the major spills events in Malaysian environments. There is an increasing trend of oil spills over the last two decades. Oil and hydrocarbons may intrude into the marine environment not only during oil spills, but simply through tanker operation and leakages. On top of that, economical development and active oil and gas production in the area will undoubtedly introduce a significant amount of hydrocarbons into the Straits of Malacca.
Presently, there are six refineries established in Malaysia with a processing capability of 514,500 bbl day− 1 (Chua et al., 2000). It is estimated that, about 34,834 metric tons of hydrocarbons wastes from industrial wastes and about 134, 227 metric tons of hydrocarbons from vehicles of Peninsular Malaysia were discharged into the Straits of Malacca in 2000 (DoE, 2001). Hydrocarbon waste from motor vehicles is probably the primary source of the atmospheric oil pollution in Malaysia.
The marine environment is the ultimate receiver of most of the land-based discharges. Oil and hydrocarbons enter the environment through a number of transportation pathways, such as atmospheric transfer, river transport and seepage. Hydrocarbons such as polycyclic compounds and polycyclic aromatic hydrocarbons (PAHs) are toxic and carcinogenic to a wide spectrum of organisms (USEPA, 1996). Therefore, it is crucial to monitor the level of hydrocarbons in order to protect the marine environment.
The status of hydrocarbon pollution in Malaysian seas
Most of the surveys and monitoring programs on oil and hydrocarbons in Malaysia are conducted on rivers, estuaries and near shore water. There are relatively fewer studies conducted in offshore water. The series of Matahari Expeditions (1985–1989), SEAFDEC Expeditions and South China Sea Expeditions covered substantial areas of the Malaysian Exclusive Economic Zone (EEZ) and they had provided comprehensive studies on the status of hydrocarbon pollution in Malaysian maritime territory. Generally, higher levels of hydrocarbons were reported in the Straits of Malacca, followed by the South China Sea off Peninsular Malaysia, Sarawak and Sabah. High concentration of hydrocarbons was reported in certain areas of Terengganu, Sarawak and Sabah EEZ. Normally, higher hydrocarbon levels were detected in the areas that were close to oilrig traffic in EEZ, South China Sea. Table 2 lists average hydrocarbon concentrations that have been reported in Malaysian seas. Total hydrocarbon levels detected in the Straits of Malacca are usually within the range 100–150 μ g L− 1; while hydrocarbons in the South China Sea off Peninsular Malaysia are always well below 100 μ g L− 1. Lower hydrocarbon concentration is normally found in the offshore waters of Sabah and Sarawak, where the level of hydrocarbons detected is always lower than 70 μ g L− 1.
Distribution of hydrocarbon in the Malaysian seas is not even. Lower levels of hydrocarbons are recorded in the offshore water and increase gradually toward the coastal water and the shore. Higher concentration of hydrocarbon is detected in semi-enclosed areas and areas with intensive anthropogenic activities. The level of hydrocarbons in Malaysian seas is generally considered safe according to Bishop (1983) who suggested that the safety level of hydrocarbons in the water and sediment should be below 100 μ g L− 1 and 100 mg kg− 1 respectively. At present, the level of hydrocarbons in Malaysian water is higher relative to that reported in Gulf of Thailand, Red Sea, Mediterranean Sea, English Channel and North Sea (Wattayakorn et al., 1998; Hanna, 1983; Ravid et al., 1985; CPSMA, 1985). Nevertheless, the level of hydrocarbons in sediment is lower than that found in North-West Atlantic Coast, Bay of Narragansett, USA and Chedabucto Bay, Nova Scotia (Marchand et al., 1982; Mulkins-Philips and Stewart, 1977).
A typical example of hydrocarbon distribution in the surface water of Straits of Malacca conducted in October 2003 is shown in Figure 2. Owing to the substantial amount of oily water discharged from land, the poor water mixing and characteristics of current movement, high hydrocarbon levels are always found at certain areas. Strait of Johor is situated on the most southern part of the Malaysian's Malacca Strait. Strait of Johor is split into two parts by the Malaysia-Singapore causeway and the water mixing is very limited. The level of hydrocarbons reported in the sediment samples of the Strait of Johor ranged from 16.19 mg kg− 1 to 1420.20 mg kg− 1. Basically, higher hydrocarbon level in sediment was found in the western part of the causeway, while lower content was recorded in the eastern entrance that faced the South China Sea. Mean hydrocarbon contents detected in the sediment of the western parts and eastern parts of the water causeway were 1420.21 mg kg− 1 and 40.56 mg kg1 respectively (Law et al., 1995; Abdullah et al., 1996). Sediments with at blackish color and hydrogen sulfide like odour were found in the western part, which indicated the absence of dissolved oxygen (anaerobic condition) in the areas. The difference in hydrocarbon contents in eastern and western causeways of the Strait of Johor is probably due to the strong current in the Straits that enhances oil biodegradation in the sediment of eastern causeway. In the western causeway, the hydrocarbon biodegradation in sediment is inactive because of the anaerobic condition.
A higher level of hydrocarbons was detected in the water of Pulau Penang compared to other areas in the northern region of the Straits of Malacca. Average hydrocarbon level in the water was 84.20 μ g L− 1. The hydrocarbon content in the sediment ranged between 8.79 mg kg− 1 and 206.62 mg kg− 1 (Law et al., 1995). Penang Island is one of the important terminals in the northern Straits of Malacca. It is being developed and upgraded rapidly for sustaining growth of the triangle development Project (IMT-GT) adopted by the three littoral states, Malaysia, Thailand and Indonesia. High hydrocarbons in the sediment of Sg. Perai estuary indicates that there is a substantial amount of oil discharged from Sg. Perai into Penang coastal waters.
Port Klang is the most important port of Peninsular Malaysia. The Klang area is highly industrialized and urbanized and packed with small fishing vessels and speedboats that transport passengers to and from Pulau Ketam. The average concentration of hydrocarbons reported in Port Klang was 140.0 μ g L− 1 which indicates that Port Klang is heavily polluted. Moving southward from Port Klang is Port Dickson. It is a famous recreational spot and there are two oil refineries situated in this area. As early as 1991, Law et al. reported that, the shallow water (10–30 m) of this area was contaminated by sewage and oil. The average hydrocarbon levels in water and sediment were 77.17 μ g L− 1 and 109.66 mg kg− 1 respectively (Law et al., 2002b). A compilation of twelve years bimonthly monitoring data on hydrocarbon distribution in coastal water of Port Dickson showed that the water of Port Dickson was consistently receiving hydrocarbon contamination. There was no significant increase (p > 0.05) of hydrocarbon level in the water, although, the level of hydrocarbon fluctuated throughout the monitoring period (Law et al., 2004b).
The South China Sea is also vulnerable to hydrocarbon pollution because of the oily water discharged by the huge number of ships that pass through this water, and because of the oily wastewater discharged by land-based activities of bordering countries. Apparently, there is some seepage of crude oil released from the sea floor of the South China Sea. High oil content was sometimes found in the sediments of the continental shelf off Terengganu where the highest value detected was up to 1332 mg kg− 1 dry sediment. High levels of oil in water, up to 1750 μ g L− 1, were also found in the vicinity of these oily sediments. Low hydrocarbon levels were found in the vicinity of most of the marine park islands; < 50 μ g L− 1 (Law et al., 2001; Law et al., 2002c). Although the level of hydrocarbons in most of the marine park islands is well within safety levels, there is a tendency of increase with tourist intensity. Tourism impacts of hydrocarbon pollution on marine park islands require careful consideration for future sustainable development.
Tar-balls in the coastal environment of Malaysia
The intensity of tar-balls stranded on beaches is a good indicator for hydrocarbon pollution. A pollution index of 10 g m− 1 of tar-balls stranded on a one-meter strip of the beach from the vegetation cover area to the water's edge is suggested by UNEP (1992). Tar-balls were found on some of the beaches with differing intensity. Table 3 lists some of the beaches of west and east coasts Peninsular Malaysia, which are contaminated with tar-balls. Approximately 7% out of the 143 beaches monitored by the Department of Environment Malaysia (2001) were found polluted by tar-balls. Based on the molecular markers of tar-balls, the abundance of higher molecular weight n-alkane and the absence of unresolved complex mixture (UCM), Zakaria et al. (2001) suggest that, the major source of tar-balls in the Straits of Malacca is derived from oily wastewaters of oil tankers from the Middle East. The tar-balls found on the east coast of Peninsular Malaysia are most probably derived from the offshore oil platform in the South China Sea (Zakaria et al., 2001).
The impacts of hydrocarbons on Malaysian marine environment
Hydrocarbons, especially aromatic hydrocarbons, are highly toxic to marine organisms. Toxicity of the petroleum hydrocarbons such as, BTEX (benzene, toluene, ethyl benzene and xylene) on marine organisms has been extensively studied over the past decade. Even though these toxic components are present at sub-lethal levels, they can cause cell damage, abnormalities in embryonic development, hatching failure, false responses in chemo-taxis, anesthesia and narcosis to the organisms (Geiger and Buikema, 1982; Dange, 1986; Law and Shazili, 1995; Law, 1997).
Malaysia is rich in biodiversity, ranging from mangroves to coral reefs. Effects of hydrocarbons on many of these tropical flora and fauna have not been well studied. It is partly due to some of the hydrocarbons being highly volatile, which make the bioassay experiments difficult to conduct. Reliable bioassay data and establishment of a safety level of various hydrocarbon compounds are crucially needed for protection of the organisms. Some studies on the toxicity and effect of hydrocarbons on various native aquatic organisms such as, Penaeus monodon, Macrobrachium rosenbergii, Lates calcarifer and other indigenous organisms have been conducted (Law, 1994; Law 1997; Law et al., 1999). Table 4 lists the LC50, IC50 and EC50 values of water-soluble fraction (WSF) crude oil for various aquatic organisms of the Malaysian environment. Assessment of the oil toxicity reveals that the WSF is the most toxic fraction of crude oil. Petroleum hydrocarbons reduce the biomass, diversity and also growth of marine bacteria. In fact, when hydrocarbons intrude into the environment, they start to alter most of the ecological processes. Petroleum hydrocarbons in sediment will pose a long-term chronic effect, especially on organisms such as Penaeus monodon, the most widely cultured shrimp in Malaysia. Extensive studies have been carried out to assess the extent of the damage of hydrocarbons on living organisms and ecosystems in the tropical waters. The WSF of Malaysian crude oil is highly toxic to phytoplankton, macro-algae, sea grasses, crustacean and fish. When oil enters into water, primary productivity will be strongly affected. The IC50of WSF crude oil on phytoplankton is about 3 mg L− 1. WSF crude oil may cause cell damage and deformation in phytoplankton such as Isochrysis galbana and Spirulina sp. Figure 3 demonstrates the effects of WSF oil on Isochrysis galbana (Hing, 2000). Spirulina sp. is able to withstand higher toxicity levels of WSF oil, but abnormality of Spirulina sp. cells are observed when the oil concentration reaches beyond 560 mg L− 1 (Tan, 2001).
The 96 hour LC50 of WSF crude oil for post larvae (PL 30) of Penaeus monodon is 13.79 mg L− 1. The chronic toxicity of WSF crude oil on this shrimp for an exposure period of 42 days revealed that there was a significant reduction in growth rate of shrimp when the oil level was higher than 3.9 mg L− 1 (Law, 1997). The EC50 value of WSF crude oil for M. rosenbergii hatching rate is 16.6 mg L− 1 (Law et al., 1999). Eggs that have been exposed to oil produced tail deformed larvae and the larvae died immediately after hatching. From the results of these studies, an interim water quality standard of 50 μ g L− 1 WSF crude oil is recommended for protecting marine organisms in the tropical sea. Figure 4 shows that M. rosenbergii exhibit abnormality after treated with WSF oil. Figure 5 shows toxicity of different hydrocarbon compounds on M. rosenbergii hatching rate. Other organisms such as mollusk, crabs and fish, the 96-hour LC50 values of WSF crude oil ranged between 15 and 30 mg L− 1(Lai and Kessler, 1992).
Oil spill combating technologies and management strategies for securing environmental safety
Malaysia is still developing policies and technologies for handling hydrocarbons and oil pollution in its water. The Malaysian government has ratified United Nations Convention on the Law of the Sea (UNCLOS) in 1996 and Marine Pollution Convention (MARPOL) in 1997. These conventions laid down the various regimes for the proper utilization of the sea, the rights and obligations of the user state, safety of navigation, marine pollution control and prevention, exploitation of living and non living resources, marine scientific research and dispute settlement. The adoption of these conventions by the Malaysian government shows their determination to secure environmental safety.
National Contingency Plan on oil spills responses
In 1994, the National Oil Spill Control Committee (NOSCC) reviewed the National Oil Spill Control Contingency Plan at the Maritime Academy of Malaysia (ALAM) in September and during the National Oil Spill Response Exercise in November at Port Dickson, Negeri Sembilan. The first National Oil Spill Response Plan was then established and implemented in 1996 for combating oil spills and aiding in beach clean-up operation. The National Oil Spill Contingency Plan was further strengthened with the establishment of oil spill beach clean-up communities at each state and a beach clean-up fund. Real time information on oil spills and their clean-up are needed for successful implementation of the National Oil Spill Response Plan to ensure effective measures are taken after oil spills. As a result, Malaysian Department of Environment (DoE), with the co-operation of other related agencies, established a surveillance program using an airborne system in 1996 to monitor the movement of oil spillage for clean-up operation. This program had been successful in providing real time surveillance on oil spill movement, distribution and location of oil spills in straits of Malacca and South China Sea.
Malaysia adopted a three-tiered approach to all aspects of oil spill preparation and response. The three tiers are: local/industry (Tier 1), area or regional councils (Tier 2) and the Department of Environment (DoE) directing the national (Tier 3) response efforts. Each tier has clear roles and responsibilities. Under the Environmental Quality Act 1974 (Amendment 1996), the Director General of Department of Environment is required to prepare and maintain the Malaysia Oil Spill Response Strategy. Of the three tiers strategy, Tier 1 is the most site-specific and includes most shore-side industry with oil transfer sites, offshore installations and all vessels required to have a shipboard oil pollution emergency plan. It caters to small spills and spill occurring within port limits, oil terminals and depots as well as at oil platforms. All Tier 1 sites and vessels are expected to be able to provide a clearly identifiable first response to pollution incidents for which they are responsible. Local authorities or local oil companies will conduct the clean up. Regional Councils and unitary authorities acting as Regional Councils provide Tier 2. These agencies are responsible for providing an operational response to oil spill incidents within their regions out to the 12 nautical miles limit of the Territorial Sea. Regional Councils will also respond to oil spills that exceed the clean-up capability of Tier 1. They will also respond to those spills for which no responsible party can be identified. The Department of Environment will offer adequate resources to Regional Councils to ensure that sufficient equipment, personnel training courses and opportunities to exercise their expertise are available for them to competently undertake this role. Two of many Regional Contingency Plans and their respective Operation Committees are: Straits of Malacca Contingency Plan, Straits of Malacca Operation Committee and Regional Contingency Plan for Sabah, Sabah Operation Committee. Regional Councils also have the responsibility of ensuring that industries with oil transfer sites within their region produce appropriate oil spill contingency plans. The Area Operation Committee will be formed to co-ordinate this Regional Oil Spill Combat Operation and chaired by an officer appointed by the Director General of Environment. Tier 3 is the responsibility of the Department of Environment. The Department of Environment manages the National Oil Spill Contingency Plan. When a spill occurs within a region, which is beyond the resources of the region, or if the cost to the Regional Council of the response is expected to be huge, the Department of Environment will assume responsibility for managing the spill response. The Department of Environment will also manage the response to any oil spill within the EEZ, but outside Regional Council boundaries (the Territorial Sea). Spills that occur outside the EEZ and over the Malaysia Continental Shelf are also the responsibility of the Department of Environment. It is activated also when the spill spreads into waters of neighboring countries. Malaysia is purchasing and maintaining oil spill response equipment, which will allow it to contain and clean up a spill equivalent to approximately 25,000 ton of persistent oil.
The National Oil Spill Contingency Plan will be used to plan and carry out a response involving international resources. Co-ordination for foreign assistance will be made by the National Oil Spill Control Committee (NOSCC), in accordance with the respective procedures of the following Regional Oil Spill Contingency arrangements: Lombok-Macassar Contingency Plan, Standard Operating Procedure for Joint Oil Spill Combat for the Straits of Malacca and Singapore, Standard Operating Procedure for Malaysia and Brunei Darussalam and ASEAN-Oil Spill Response Action Plan (ASEAN-OSRAP).
Research on oil pollution in Malaysia
Adverse effects of hydrocarbons have triggered much scientific research on various aspects of hydrocarbons pollution in Malaysia. Scientists are actively conducting research which aim to restore and safe guard the marine environment from oil pollution. Generally, Malaysian scientists are active in the field of survey and monitoring toxicity and impacts on organisms, indicators for oil pollution, remote sensing and GIS, environmental management and policy, biodegradation, biotechnology and chemical treatments of oil in water and sediment, food safety, and environmentally friendly machinery and products.
An indicator of oil pollution is essential for indicating the status of oil pollution in the marine environment. Feasibility of employing some marine organisms as bio-indicators for oil pollution is actively researched; the Green-lipped mussels and some marine benthos that accumulate polycyclic aromatic hydrocarbons (PAHs) being potential bio-indicators (Mashinchian et al., 2002). Other than the benthos, Law et al. (2004a) also proposed oil-degrading bacterial populations as indicators. Oil biodegradation seems to play an important role in removing hydrocarbons in the sea. Marine bacteria appear to be the major break-down agents of oil in the sea (Bartha, 1986). Several studies on the isolation and identification of active oil degrading bacteria have been reported in Malaysian seas (Pozan et al., 2002; Law and Teo, 1997). Active oil degrading bacteria were isolated from areas that contaminated with high level of hydrocarbons. Most of the oil-degrading bacteria isolated from Malaysia marine environment are Pseudomonas, Acinetobacter and Vibrio bacteria. These oil degrading bacteria are very active and their maximum specific growth rates on aromatic hydrocarbons are much higher than those oil bacteria present in the temperate areas (Law and Teo, 1997; Aldrett et al., 1997; Oudot, 2000). The difference in the oil degrading bacterial activity is most probably due to the temperature effect in the tropics. Some of these oil bacteria can degrade 50–60% of the crude oil alone within two days. A combination of them can degrade higher than 65% of the crude oil (Hii and Law, 2004). These active oil-degrading bacteria are very useful in clean-up oil in soil as well as in water.
Removal of trace amounts of toxic aromatic hydrocarbons in water using agricultural by-products is another thrust area of research carried out in Malaysia. Some of the absorbents such as shrimp shells, palm oil husk, coconut husk and synthetic sponges are among the materials that exhibit excellent capabilities in oil adsorption ability. A combination of them can reduce aromatic hydrocarbons down to 20 μ g L− 1 from seawater containing 10 mg L− 1 WSF oil. This level is safe for shrimp hatchery operation. Hence, an incorporation of the materials may produce an excellent filtration technique for cleaning oil in the environment.
It is believed that environmentally friendly products and machinery will be produced in the future to regulate hydrocarbon pollution. Among the research, engines with high combustion efficiency and less energy consumptions will be gaining the public's attention. Development of alternate energy sources will also contribute positively towards the reduction of hydrocarbons input in this country.