A recent study led by Curtin University has found that the environmentally sensitive mangroves near Mauritius are still grappling with oil contamination. This comes three years after the bulk carrier MV Wakashio spilled a thousand tons of a novel type of marine fuel oil after running aground on a coral reef close to crucial Ramsar conservation sites.

Dr. Alan Scarlett, the study’s lead researcher from the Organic and Isotope Geochemistry Centre at Curtin’s School of Earth and Planetary Sciences, explained that their research showed a near-identical match between the chemical signature of the oil detected in the mangrove sediments and the Very Low Sulphur Fuel Oil (VLSFO) spilled by the Wakashio in 2020. This marked the first recorded contamination involving this type of fuel.

“Local communities in Mauritius have reported oil contamination in the mangrove wetlands since the Wakashio incident, but there was no official acknowledgment of the source until now,” said Dr. Scarlett. “Identifying this contamination is critical for both the Mauritian population and global understanding, as we have limited knowledge of how this new marine fuel behaves following a spill.”

Advanced chemical techniques were employed to analyze samples from the mangrove wetlands, including from a reference site believed to be unaffected by the spill. “We ascertained that the reference site was devoid of oil contamination, while another site contained oil from the Wakashio’s fuel tanks,” Dr. Scarlett explained.

They found that significant weathering and biodegradation had occurred over the three years since the spill, reducing many toxic compounds in the spilled oil. Nevertheless, the continued presence of the oil could potentially pose a risk to the delicate mangrove ecosystem.

In a prior partnership with the Woods Hole Oceanographic Institution, the research team from Curtin was able to obtain a unique chemical signature of the spilled oil, which helped them confirm its presence in the mangroves.

The team also used models from the National Oceanic and Atmospheric Administration’s oil spill scenario tool, WebGNOME-ADIOS, to compare the behavior of the Wakashio’s VLSFO with conventional marine heavy fuel oils. “Our models indicated that more of the Wakashio’s fuel would evaporate, disperse naturally, or sink compared to traditional fuels. However, gauging the impact on organisms remains a challenge,” Dr. Scarlett noted.

The research, titled “Very Low Sulfur Fuel Oil spilled from the MV Wakashio in 2020 remains in sediments in a Mauritius mangrove ecosystem nearly three years after the grounding,” was published in the Marine Pollution Bulletin.