April 18, 2014 — In the months and years following the 2010 Deepwater Horizon oil spill, telling fact from fiction regarding seafood safety and ecosystem health was supremely difficult. Is Gulf seafood safe to eat or not? Are there really deformed shrimp and black lesion-covered red snapper? Will the Gulf ever be clean again?
In the months and years following the 2010 Deepwater Horizon oil spill, telling fact from fiction regarding seafood safety and ecosystem health was supremely difficult. Is Gulf seafood safe to eat or not? Are there really deformed shrimp and black lesion-covered red snapper? Will the Gulf ever be clean again?
A large part of the confusion was due to the connected, yet distinct, seafood issues surrounding the spill. Whether the seafood was safe for humans to eat was mixed with stories of the future of Gulf fisheries; harm done to wild fish was conflated with health of the seafood supply.
To clear up some of the confusion, here are seven topics of concern, some still unresolved, about the Gulf Oil Spill, brought to you by the Smithsonian Ocean Portal and the Gulf of Mexico Research Initiative (GoMRI). These should help you better understand the spill’s effects on seafood and wildlife.
#1: Once oil enters the Gulf, it will stay there indefinitely.
The fate of oil is difficult to assess because it isn’t any single chemical; it’s instead a complex mixture of different-but-related chemicals that started out as dead plants and animals. Buried deep in the earth and placed under heat and pressure for millions of years, their bodies break down and the hydrogen and carbon rearrange into the components of oil. First they bond together to form long chains. Over time, some of those chains loop into strings of two to seven rings.
Crude oil contains the whole spectrum of these chemicals, from large to small; they degrade at different rates, and some can damage wildlife while others are harmless. The main question then is how long the dangerous chemicals in oil will persist in the Gulf.
When the spill began, many people immediately assumed that oil entering the ecosystem would never break down. That’s because we are so familiar with environmental contaminants that stick around for a very long time, such as DDT, CFCs, or mercury. These take a long time to degrade naturally (or don't at all in the case of mercury), and hence persevere in the environment for a very long time.
In contrast, oil “can be readily degraded,” said Ed Overton, who studies the fate of oil after spills at the Louisiana State University in Baton Rouge and is a lead researcher with GoMRI. “We’re talking about a completely different type of chemical.”
Oil that dissolves into or mixes with water can be broken down by bacteria—and, fortunately, the Gulf of Mexico is loaded with oil-eating bacteria. Between 560,000 and 1,400,000 barrels of oil leak into the Gulf every year from natural oil seeps, and where there's a source of energy, you can generally find bacteria. In the case of the Deepwater Horizon blowout, the spill originated in the deep sea where the oil-degrading bacteria are also found, which helped them to start breaking down the oil quickly.
But for those bacteria to do their job, they need oxygen, and lots of it. As such, the most dangerous place for oil to end up is in marshes. There, oil can easily get buried in the low-oxygen soil and bind with the sediment, where it cannot be broken down and remains until it is flooded out by a storm. And if it sticks around there, being slowly released by flooding events over the course of decades, it can do harm to the 98 percent of commercially-important Gulf species that are dependent on saltwater marshlands during their lifecycle.
It's also possible that some oil sank as it was colonized by bacteria, sticking to and clumping with other floating particles on its way to the deep sea. In some cases, it was buried under the seafloor, where bacteria couldn’t access it as well. So if there is oil that stuck around in the Gulf, marshes and buried seafloor sediments are the places you'd find it.