Shell Malaysia is an exploration, and production (EP) oil and gas company in Malaysia, a contractor to the national oil company, Petroliam Nasional Malaysia (PETRONAS), operating in Malaysia since 1910. Initially, explorations and production of oil and gas were land-based, but are now entirely in the marine environment, since the late sixties.

In 1981, the first of a series of quantitative environmental assessment studies was carried out on the nearshore marine environment at the crude oil terminals at Bintulu, Lutong and Labuan, as well as offshore oilfield platforms – Temana A, Temana B, West Lutong a, B & C.

It was not the company's intention right from the beginning to assess every living resource in area of its operations, but through carefully selected parameters that were relevant and effects that are measurable as indicator for environmental stress. The resource selected for quantitative study was the macrobenthic communities, which are important indicators of water quality. The individual is referred to as macrobenthos. These macrobenthos are relative long-lived and do not move far away once they have settled in a particular area.

In the first environmental assessment study in 1981, an impact-reference sampling design was adapted because of the absence of historical baseline data for the macrobenthic community. Reference sites were chosen to be as similar as possible, in term of exposure and geomorphology, to impacted sites. In subsequent assessment studies, reference sites may not be necessary.

Three environmental assessment studies are used to illustrate the use of macrobenthos as pollution indicators in Shell Malaysia EP operational areas. The first case is the use of oil-based mud at Erb West oil field at water depth of 60m. Pre-drill and post-drill environmental assessments were performed. The macrobenthic community was drastically reduced within the 100m from drilling center. This reduction correlated with the elevated level of hydrocarbons.

The second case was the effects of effluent discharge from Labuan crude oil terminal, one of the first sites chosen by Shell Malaysia EP for environmental assessment in 1981. This site was again studied in 1993 and 2004. The changes observed in the structure of the macrobenthic community in these 3 studies showed a pattern similar to that of organisms responding to organic enrichment. The analysis of the macrobenthos data indicated the site studied there has improved from a polluted environment in 1981 and 1993, to one of a much cleaner environment in 2004.

The third case was the recovery of intertidal macrobenthos from crude oil spilled from Bintulu crude oil terminal in 1996. The analysis of the macrobenthos data indicated the recovery of the macrobenthos within three months in exposed intertidal zone, but more than a year in enclosed bay.

It is very important that raw data of any environmental studies be included in the reports, which are accessible for review.

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