An article published last week in the “Environmental Science and Technology” journal provides new insight into the effect of the April 2010 Deepwater Horizon oil spill. The paper, a collaboration between Associate Professor of Earth and Environmental Sciences John Kessler and researchers at Texas A&M University, concluded that bacteria consumed 200,000 tons of oil to date.
The findings were made possible through the Rapid Response Award, a grant from the National Science Foundation given to researchers who wish to conduct research in the midst of crisis — crisis wherein Kessler et al. found a suitable opportunity to expand their knowledge base of natural gases, specifically methane.
The team studied the spill primarily to “untangle how the oceanic methane system contributes to the global climate system since methane was the most abundant molecule released during this disaster,” Kessler explained. “Fundamental questions are not known and [the spill] gave us the opportunity to study them.”
Aboard a fleet of ocean research vessels, Kessler and his party took measurements of methane levels present in the seawater. The team realized that their instruments and techniques could conveniently measure a good portion of the released oil and natural gas as well.
This startling discovery revealed two key phenomena: an increase in carbon dioxide levels and a decrease in oil, natural gas and oxygen levels — a combination that crystallized their conclusion that bacteria had consumed the oil.
If the gas had merely dissipated or evaporated there would be a decrease in oil and gas but not in oxygen, according to Kessler.
“The only way you can get a loss of oxygen like that is through a natural biological process — through [bacterial] respiration,” he said.
The use of oil dispersants is one reason that may have contributed to this bacteria feast. In an effort to limit oil from reaching the lush biodiversity on the ocean’s surface, oil dispersants were injected deeper in the water at the oil’s source.
“Our research gives a first glimpse into the effectiveness of dispersants injected at the seafloor where oil was gushing out,” Kessler said.
The data showed a direct correlation between oil dispersant application and oil consumption, likely due to the dispersant breaking the oil into smaller molecules that were more accessible to bacteria.
The amount of oil and gas that the dispersants helped the oceanic bacteria to ultimately consume is striking — 200,000 tons.
The effects of this massive feast are not yet completely understood. What is understood though is that consumption of the spilled oil yields carbon dioxide — roughly 60 percent of the oil and gas become carbon dioxide directly while 40 percent is converted to biomass, which has the potential to ultimately decay into carbon dioxide. Increased carbon dioxide levels lower the ocean’s pH and can potentially contribute to climate change.
While this was the largest spill in U.S. history, the results will probably not pose a global threat.
“[The area of the spill] is too small compared to the entire planet,” Kessler said. “However, as [geoscientists], what interests us is what happened on the local scale and if what we learned from [the local scale] we can extrapolate to the global sphere as we seek to understand how the planet functions naturally.”
Fagan is a member of the class of 2014.