As the fifth anniversary of the Deepwater Horizon oil disaster approached, I was asked countless times: How bad is the Gulf of Mexico today?
Maybe television dramas should be blamed for creating false perceptions on what science can do and how fast it can be done. But for scientists, the fifth anniversary is the 1,826th day since the damaged Macondo oil well began releasing about 75,000 gallons of oil per hour each day for 87 days into the Gulf.
At the time, the Gulf of Mexico was not pristine, and scientists lacked baseline knowledge about preexisting conditions. In an area full of oil rigs, where a spill was a good bet (if not inevitable), we had not conducted extensive, long-term research that would have captured what the Gulf was like before it was dosed with oil. Surprisingly little was known about the presence or absence of potentially toxic petroleum hydrocarbons on the seafloor even around the massive drilling rigs that inhabit the Gulf. That's a lesson we should learn before we ever put the first oil rig in the Arctic Ocean.
The Gulf spill contained variables we hadn't invested in learning much about: deep currents that would transport chemicals, for example, and which organisms are most vulnerable to oil. And it had inputs we couldn't control, such as excess nutrients from the Mississippi River that promote anoxic "dead zones.''
In one study published in November 2014, my colleagues and I examined evidence of contamination on the seafloor near the damaged well. It was a massive effort, starting with little baseline information. We could account for 2 to 16 percent of the total oil discharged during the accident falling within a 1,250-square-mile patch on the deep seafloor. That was in 2012. I can't say how much oil is still present today.
Similarly, scientists investigated impacts of the spill on coral communities 5,000 feet deep on the bottom of the Gulf (which they happened to know about only because they had conducted basic research searching for life in extreme environments). Scientists examined the corals in the fall of 2010 and published research in 2012 showing that some corals in the path of the oil fallout were much less healthy. They revisited those corals in 2011 and recently published that the corals' recovery was mixed. We don't know about their conditions today.
So how is the Gulf today? It is far from a graveyard predicted by some experts in the throes of the spill, but it's not a picture of health. Some salt marshes such Barataria Bay, La., are still oiled. But we find little oil on most beaches or rocks, and some of the most toxic compounds are no longer present. We found that sunlight photochemically broke down a significant amount of the oil, but we yet don't how toxic these transformed products are. (We have also shown that many oil samples we find in the Gulf are not from the Deepwater Horizon.) We are still investigating many complex, longer-term, harder-to-see consequences in the Gulf ecosystem.
To get a handle on the health of the Gulf or any other marine ecosystem, we need to invest in methods to examine them like bodies, not bodies of water. We must continue the effort to conduct difficult deep-sea detective work and to develop new technology to probe, monitor, and report in timely ways on a myriad biological, chemical, and physical conditions in the Gulf. Otherwise, we may not get fully satisfying answers on the next anniversary of Deepwater Horizon.
Chris Reddy is a marine geochemist at the Woods Hole Oceanographic Institution.