The intentional release of an estimated 11 million barrels of oil during the 1991 Gulf War was the largest oil spill in history. An assessment of the physical, chemical, and ecological impacts of this spill shows that, 12 years later, oil residues and habitat modifications continue to have toxic effects on intertidal communities. As of 2003, there are an estimated 8 million cubic meters of oiled sediment remaining along the 803 km of impacted shoreline in Saudi Arabia. Of this volume, 45% occurs in muddy tidal flats and 23% in salt marshes and mangroves. Much of the oil in these sheltered habitats occurs as oiled crab burrows, with liquid oil remaining in the burrows to depths that exceed 50 cm. These habitats show the lowest degree of ecological recovery since the spill, with 87% of the upper intertidal zones of mangroves and marshes and 71 % of muddy tidal flats having reduced species richness and a disturbed community structure. Those habitats exposed to the greatest amount of wave activity contain the smallest amount of residual oil; however, on outer sand beaches, the oil is commonly buried to depths exceeding 1 m. The factors that affect the ecological recovery of the intertidal habitats include: 1) The chemical toxicity of the oil residues; 2) the physical toxicity of heavy and hardened oil residues; 3) other physical barriers that affect seed germination of plants, settlement of larvae, and burrowing; 4) limited sources for recruitment of biota; 5) reduced hydrological functioning of tidal channels. This study shows the importance of oil removal as the first phase of habitat recovery. It also indicates the potential for large-scale damage by blatant acts of eco-terrorism.

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