More Mysterious Dark Substances Seen In Ocean Around Mauritius After Oil Spill

The giant puzzle surrounding the Mauritius oil spill keeps getting bigger almost two months on, as more pieces are added, and fewer questions are answered.

On Sunday 20 September, local kitesurf instructor, Denis Labeauté filmed a mysterious dark substance in the waters moving around the South of the island.

Based on the direction of the currents at this time of year, the substance was coming from the direction of the giant Japanese ship, the Wakashio, and the subsequent oil spill. It could also have been coming from the direction of the sunken front part of the vessel, the part of the vessel still stuck on the reef, or the cleanup operation, that continues under strict secrecy.

Given that the Wakashio was sunk in an undisclosed location and a full inventory has still not yet been disclosed of what was on the vessel, it is unclear whether the dark substance could have originated from the vessel.

Just 15 days earlier, on 5 September, a mysterious brown substance had turned the pristine blue coral lagoon of Blue Bay Marine Park into a much darker color, causing concern across the country.

Government scientists the following day said that this dark substance was algae.

Algae as a precursor to ocean deadzones

In oil spills elsewhere in the world, algae blooms have been associated with ocean deadzones.

Coral reefs require clear waters which are free from particular nutrients that could cause a harmful algae bloom. Certain cleanup operations use either organic fertilizers or chemicals to try eradicating the presence of oil. This is usually done to rapidly remove the visible trace of oil, but could cause longer term issues.

Harmful algae blooms could end up creating many more serious cascading effects on coral reefs. For example, the brown algae could be an indication that calcification of corals may be being prevented. This could be a precursor to a phase change of the corals.

US Marine toxicologist, Riki Ott, has seen her fair share of oil spills. She is the executive director of the ALERT Project which is supported by high profile US Environmental NGO, Earth Island Institute that has taken a stand against harmful oil spill clean up operations.  She expressed concern with what she is seeing in Mauritius.

“The emergence of algae following an oil spill is a worrying sign. Oil spills usually smother algae first. Then in time, fragile algae that live in clean environments are replaced by more opportunistic algae that can survive in polluted environments. When substances such as nitrogen and phosphate are added, as in bioremediation, the algae can also bloom. Algae blooms are linked with dead zones, because the algae bloom consumes the oxygen in the water.”

Asked whether the algae bloom could also be a result of the oil spill clean up operation, she said, speaking to Forbes “the presence of algae could be an attempt to accelerate biodegradation of oil by nutritional supplementation. Oil is an overdose of carbon, so oil-eating bacteria growth is limited by phosphorus and nitrogen. Products such as surface washing agents or bioremediation agents with phosphates could cause this. This would stimulate the bacteria and and also the algae, effectively acting as a fertilizer for the algae. This could be particularly damaging for coral reefs.”

Riki went on to explain her experience with the Exxon Valdez oil spill in Alaska in 1989, and the legacy of bioremediation agents there.

“What was foisted on us during the Exxon Valdez as a bioremediation agent, was actually industrial solvent 2-butoxyethanol carrying some phosphate. It interacted with oil more like a dispersant. This turned out to be really deadly for the workers. Really bad.”

150 square kilometers cordoned off