Many of us still remember the BP oil spill from five years ago, when 205 million gallons of oil were accidentally spilled into the Gulf of Mexico from oil drill platform that exploded. Since then, we haven’t heard much about how the ecosystem is recovering, if at all, and what the real impact of such a tragic event will be in the future for our ecosystem.
Scientists have known where most of the oil went, but until recently several million gallons had gone unaccounted. Two recent studies suggest the oil sank to the bottom, creating a huge, possibly dangerous stain on the seafloor. Makes you want to think twice before wanting to consume any seafood from the Gulf waters.
“This is going to affect the Gulf for years to come,” says Florida State University oceanographer Jeff Chanton, lead author of the newest study. “Fish will likely ingest contaminants because worms ingest the sediment, and fish eat the worms. It’s a conduit for contamination into the food web.”
Why did the oil sink when oil normally floats on water?
Chanton says this is the case and lots of oil from the 2010 BP spill did float at first. But some of it probably got caught in clumps of clay and slime, causing it to quietly slip down to the seafloor.
“Bacteria in the water produce a mucus when they’re exposed to oil,” Chanton says. “These clumps of mucus aggregate, and pick up clay particles because the Mississippi River is nearby. Clay provides ballast, and the larger these particles become, the faster they sink. “
The BP oil spill of 2012 was by far the largest in U.S. history, and only a quarter of it was cleaned at the surface or captured by deep-sea containment systems. Another quarter of the oil naturally dissolved or evaporated, according to a U.S. government report, and about 24 percent was dispersed, either naturally or due to the controversial use of chemical dispersants.
It is impossible to determine how much actually ended up on the seabed, but the new study estimates it’s between 6 million and 10 million gallons.
Natural oil seeps are common in the Gulf of Mexico and they are even helpful for small populations of bacteria, which have evolved to eat petroleum for energy. Those microbes initially played a key role in cleaning up the spill, devouring about 200,000 tons of oil by September 2010.
However, now that all the oil has sunk to the seabed, lower oxygen levels in the deep ocean may help preserve the oil by impeding the ability of bacteria to eat it, according to Chanton. This means the oil could pose a vast danger to local sea life, passing from worms, tilefish and other bottom feeders up through the food web.