Attacks by the United States and Iran on oil tankers and other vessels around the Strait of Hormuz are increasing the risk of a major spill in the Gulf. On September 8, the United States struck five Iranian oil tankers, three days after hitting three others; Iran has also said it targeted tankers and US-linked vessels.
As of September 7, 42 tankers were waiting to transit the strait, including 18 carrying oil. Their combined estimated capacity was 1.76 million cubic metres of oil and petroleum products — about 11.1 million barrels, or roughly 11 percent of global daily oil demand.
A crowded waterway under attack
The latest escalation followed Iranian ballistic-missile launches towards a US aircraft carrier and navy destroyer near the strait, according to US Central Command. Iran later said it had targeted three tankers using what it called an “unauthorised route” through the waterway, as well as three US-linked vessels elsewhere.
US Central Command said that on September 5 its forces struck three Iranian crude-oil tankers: one off Kharg Island, another near Jask and an unladen tanker in the Gulf of Oman after its crew was ordered to abandon ship. Since the war began, two incidents have involved minor oil spills and six have caused fires. For additional context, see “Oil spill from stranded tanker spreads off southern Oman”.
Spills are already affecting waters off Oman
Oil has been leaking from the Caroline Bezengi after it ran aground about 22 nautical miles, or 41km, off Oman following a suspected explosion reported by its crew in early June. Reuters estimated that the tanker was carrying 800,000 barrels of oil, while Oman’s Environment Authority warned the spill could affect about 40km of coastline near Ras Madraka and Masirah Island.
The Minoan Pioneer, a Liberian-flagged bulk carrier, caught fire after being struck by an unidentified projectile off Oman on August 3. Satellite imagery recorded on August 10 showed a large slick near Qeshm Island and another near Sirri Island. Experts said the Qeshm slick likely came from the Minoan Pioneer but could not independently confirm its source.
What a larger spill could damage
The Gulf is a shallow, semi-enclosed sea with limited water exchange with the wider Indian Ocean. Its coral reefs, seagrass beds, mangroves, mudflats and salt marshes provide feeding and nursery grounds for fish, turtles, dugongs and migratory birds, while supporting fisheries and helping protect coastlines. A related part of this story is covered in “Tanker salvage starts as Oman oil spill expands offshore”.
Oil can poison or smother plankton, fish eggs, larvae, corals, seagrass and mangroves, and can remain trapped in coastal sediments. A June study by the University of South Florida, based on satellite imagery, found that oil spills in the Gulf and Strait of Hormuz were four times higher in March than a year earlier, with frequent leaks observed around vessels trapped in the area.
Risks to coastal communities and water supplies
The Gulf states rely primarily on desalination to supply water to their nearly 65 million people, and Iran has desalination plants along its southern coast. Oil near seawater intakes can reduce raw-water quality, interfere with treatment and, in severe cases, require temporary operating restrictions. The development of this issue can be followed in “How warmer seas are changing marine life around Britain”.
Hussein Samh Al Masroori of Sultan Qaboos University said the risk depends on the spill’s location, currents, the distance and depth of an intake, and treatment technology. He said early detection, monitoring, modelling and advanced treatment can reduce the risk by keeping contaminated water from entering desalination systems.
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