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On this. day: the Deepwater Horizon oil spill

On April 20, 2010, an explosion on the offshore oil drilling rig, Deepwater Horizon, was the catalyst for the largest accidental marine oil spill ever recorded. The explosion claimed 11 lives, and the underwater blowout that followed released a massive volume of crude oil into the ocean. Much has been discussed about the explosion’s myriad of causes, but less about the impact the oil spill continues to have on the environmental landscape to this day.     

The devastating impacts on marine wildlife

Over the 87 days that followed the explosion, the blowout released an estimated 3.19 million barrels of oil. This 795 million litres wreaked havoc on an estimated 10,000 square kilometres of the Gulf of Mexico, finally washing up along a 2000 kilometre stretch of coastline.

The external effects of oil spills are always the most noticeable, and are generally the most immediately debilitating for marine wildlife in the vicinity. This was certainly the case with the Deepwater Horizon oil spill. Thousands of animals were affected, explains Associate Professor Julie Mondon from Deakin University’s School of Life and Environmental Sciences.

‘The initial and most immediate effect was physical smothering, evidenced by oil-soaked turtles, fish and birds floating in the oceanic slick, and washed up on coastal shores. Oil is sticky, difficult to remove from skin, feathers and fur, and highly toxic,’ she says. When coated in oil, seabirds struggle to fly, and fish, turtles and marine mammals struggle to swim. Oil that seeps into insulating feather and fur layers can cause hypothermia and even death.

The internal effects are just as dangerous to marine wildlife. ‘Oil ingestion and inhalation of volatile fumes results in issues like gastrointestinal and blood disorders, abnormal kidney functioning, gill and liver damage, alteration in heart and respiratory rates, and cardiac arrest in juvenile and adult organisms,’ Assoc. Prof. Mondon adds.

However, it wasn’t only the marine wildlife that suffered. Recent studies show that the oil from the spill was found at even greater distances than first thought, and helped destroy vital habitats needed for wildlife survival. The oil damaged the roots of coastal saltmarsh, seagrass meadows, mangroves and mudflats, killing them and causing ‘significant beach and sediment erosion,’ Assoc. Prof. Mondon explains. This was the case with Cat Island, an important saltmarsh rookery that a mere seven years after the disaster, has completely disappeared. The oil sped up the natural erosion process tenfold.

The criticised clean-up efforts

With a disaster of this magnitude, the clean-up effort is massive. ‘The sheer size of the spill required 47,000 personnel, 7000 vessels and $14 billion to cover the cost of the emergency spill response operation,’ Assoc. Prof. Mondon says.

The clean-up focused on three areas; containment, dispersal, and removal. Assoc. Prof. Mondon describes it as a ‘major effort to minimize the volume of oil reaching the coast’. ‘Kilometers of containment and absorbent floating booms were used in an attempt to trap and contain floating oil. Skimmers were deployed to skim oil from the surface and transport by ship from the site. Large filter systems were deployed to separate the oil form the water. Surface oil was also ignited after being contained by fire-proof booms.’

However, there was criticism at the use of oil dispersant, Corexit, which is banned for use in both the UK and Sweden. An oil dispersant is a mixture of emulsifiers and solvents that helps break oil into small droplets, making it easier for bacterial microbes to remove the oil naturally. However, Corexit is toxic, which adds to the danger of the spill. As Assoc. Prof. Mondon explains, ‘toxic but effective dispersants such as Corexit “displace” the oil relatively quickly; bacterial microbes remove it entirely.’

‘In all cases the approaches used were deemed the “best option” at the height of the emergency. In retrospect, the approaches used were effective in minimizing the oil slick under very difficult conditions, but due to the sheer magnitude of the spill not effective in preventing oil from reaching the coast,’ Assoc. Prof. Mondon says.

 The learnings for future oil spill disasters  

It’s currently difficult to quantify the impact that the disaster has had. While wildlife populations in general appear to have recovered, this can’t be claimed with any certainty. There are conflicting reports on whether the environment is rebounding.

‘In the aftermath of every disaster we learn something new,’ Assoc. Prof. Mondon says. ‘Much has been learnt in relation to responding to mega-spills at sea, particularly the difficulties associated with continuous release under extreme pressure and over extended time frames. As bad as the oil spill was, it has also enabled extensive and ongoing research to be conducted on the biological and ecological impact of oil exposure on wildlife in both the deep sea and coastal environments; information that will significantly improve our ability to accurately assess the risk of future oil spills affecting marine ecosystems.’

Interested in helping save Earth’s marine habitats and wildlife from the next disaster? Check out Deakin University’s Bachelor of Environmental Science (Marine Biology)

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Assoc. Prof. Julie Mondon
Assoc. Prof. Julie Mondon

Associate Head of School, Warrnambool
School of Life and Environmental Sciences, Deakin University
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