Robotic vehicles study oil spill
Dr Michael Jakuba managed two vehicles
that collected samples from the oil plume,
an important process due to the legal and
financial implications of the spill.
Image: The University of Sydney

On the evening of 20 April, 2010, a methane explosion on the Deepwater Horizon drilling rig, 66km off the coast of Louisiana, triggered the worst environmental disaster in US history.

The explosion cost eleven lives and caused widespread and extreme environmental damage. Over the next three months, around 4.9 billion barrels of crude oil flowed into the Gulf of Mexico.

Although the leak has now been secured, speculation continues about the extent of the pollution caused by the disaster. Satellite images of oil on the sea surface were at first used to estimate the spill, but underwater camera footage later showed oil gushing below the surface as well.

In the weeks following the spill, Dr Michael Jakuba, an engineering postdoctoral fellow from the University of Sydney's Australian Centre for Field Robotics, joined a team of scientists led by the Woods Hole Oceanographic Institution (WHOI) to investigate the sub-sea plume, and to map and confirm its origin.

"Our goal was essentially to follow up on some earlier indications that there was a plume of oil or something fairly deep and resident beneath the ocean's surface," says Dr Jakuba, who completed his PhD at Woods Hole.

The team's mission was to investigate the spatial extent and dynamics of the plume, and collect samples for analysis in government laboratories, a requirement of the US law for environmental disasters.

"Obviously there are pretty significant legal and financial implications from spills of this magnitude, so any kind of sample work that might be brought up in the court of law has to go through pretty rigorous procedures in terms of analysis and oversight,"says Dr Jakuba.

His role was to manage the two vehicles that were used to collect samples from the plume. The first, armed with chemical sensors to detect dissolved hydrocarbons, was lowered from the ship on a cable and was used to locate the plume, identify its vertical extent and collect samples.

The second was a robotic vehicle called Sentry, for which Dr Jakuba has written operating software. It excels at moving horizontally through the water and can be very precisely navigated. "We used the robot to basically map out the horizontal extent of the plume," he says.

Dr Jakuba was previously part of a team that guided a remotely operated underwater vehicle to the Mariana Trench in the Pacific, the world's deepest ocean bed.

"I'm interested in how we can use undersea robots to more intelligently analyse chemical phenomena in the ocean," he says. "My research is in the area of adaptive surveying and semi-supervised surveying. Surveying the chemical phenomena intelligently requires surveying efficiently, and it is best done through adaptive means. If you can adapt a vehicle's trajectory to spend its time in the area of interest, in the plume in this case, then you end up with a lot more data than you would if you just completely pre-planned everything."

Dr Jakuba's research has focused on hydrothermal vents, with the specific aim of identifying hydrothermal vents on the sea floor.

These are structures that occur throughout the 60,000km worth of mid-ocean ridge that spans the entire globe, mostly in the centre of oceans, like a big mountain chain down the centre of the South and North Atlantic.

Sea water is circulated through the ocean floor and warmed by nearby magma or some other heat source, and then basically sprayed out of the sea floor as heated liquid that contains a number of chemicals that can be used as energy sources to sustain chemosynthetic ecosystems.

There are still some big questions about the biology of hydrothermal vents: how they affect the chemistry of the oceans, their effect on the heat content of the oceans, and how the animals that live there propagate from one vent to another. Dr Jakuba's PhD project involved developing methods for analysing the chemical data coming back from the vehicles and coming up with estimates of where the vents were likely to be on the sea floor.

"Since then I've started to realise that intelligently surveying the plumes, rather than just trying to locate their sources, may be of more general interest, and not just for hydrothermal plumes. We've got sewage outfall plumes, for example, and their environmental impacts are dependent on dosages that the downstream environment experiences. Robots capable of making simultaneous measurements of that environment, for instance photographs of the seafloor combined with chemical data from within the plume, could augment the sophisticated models currently used to predict the environmental impact of sub-sea industrial plumes."

Intriguingly, after the WHOI team finished its investigation in the Gulf of Mexico, other researchers using DNA studies discovered that much of the plume quickly vanished as a result of natural processes.

"In fact, two or three weeks after the well was finally capped, all evidence of the plume in the mid-water column had basically disappeared. Presumably it had been consumed by bacteria," says Dr Jakuba.

"The thing youve got to understand about oil spills, in the Gulf in particular, is that there are a large number of natural seeps. So oil and hydrocarbons are always being spilled into the Gulf, and always have been.

"This was a big thing, but there are animals and bacteria in the Gulf that thrive on exactly this phenomenon. Not usually not on this scale, but nevertheless nature does have its mechanisms to help."

Editor's Note: Original news release can be found here.