'Catastrophic' oil spill still polluting idyllic Mauritius wetlands three years on

A new analysis by Australian researchers has confirmed that the pristine mangroves around Mauritius are still contaminated with ship fuel oil, three years after the MV Wakashio oil spill. In July 2020, the Japanese bulk carrier MV Wakashio ran aground on a coral reef about 1.6 kilometers off the coast of Mauritius, with environmentalists warning that the severe consequences could last for decades.

Due to the long-term impact of the waves, the ship broke apart, and an estimated 1,000 tons of new type of ship fuel oil leaked into the Indian Ocean near the internationally recognized Blue Bay Marine Park. Although this spill was smaller than some of the world's largest spills, such as the 2010 BP Deepwater Horizon spill in the Gulf of Mexico, it occurred near some of the world's most sensitive marine habitats, including coral reefs, mangroves, and seagrass beds.

Dr. Alan Scarlett of Curtin University stated, "The local community in Mauritius has been aware of oil contamination in the mangrove wetlands since the Wakashio spill, but there has been no official confirmation of the source of the contamination." Scarlett and his team at Curtin University's Western Australian Organic and Isotope Geochemistry Centre collected samples from the mangrove wetlands and analyzed them using advanced chemical techniques.

Scarlett said, "We confirmed that there was no oil contamination at the reference site, while another site contained oil from the Wakashio's tanks." The chemical "fingerprint" of the oil they found in the mangrove sediments almost perfectly matched the very low sulfur fuel oil (VLSFO) that leaked from the Wakashio in 2020. At the time, this was the first recorded spill involving this type of fuel.

In the years since the incident, the spilled oil has undergone significant weathering and biodegradation, reducing the levels of many toxic compounds. Scarlett said, "However, the continued presence of oil may still pose unknown risks to the sensitive mangrove ecosystem."

The Curtin University research team also used models developed by the US National Oceanic and Atmospheric Administration to compare the behavior of the new type of oil with traditional heavy ship fuel oil. They found that more of the fuel would evaporate, naturally disperse, or sink compared to traditional fuels, but its impact on organisms remains unclear. The full results of this study were published this week in the journal Marine Pollution Bulletin.