For most Americans, the Deepwater Horizon oil spill
ended a few months after it began. Oil giant BP finally capped the mile-deep Macondo oil well on July 15, 2010, and the U.S. government declared its summer-long scourge "effectively dead" by mid-September.
But across the northern Gulf of Mexico — which absorbed 200 million gallons of crude oil in 2010 — the disaster still isn't over. This Earth Day
marks its third anniversary, highlighting a gradual shift from in-your-face emergency to subtle, behind-the-scenes villain.
"You can think of an oil spill as an evolving event," says Samantha Joye, who runs the University of Georgia's Joye Research Group
and has become a leading expert on the spill. "There are acute impacts — things like oiled birds and marine mammals, ecosystems that were altered. Then there are chronic consequences — long-term impacts where we might not see an immediate effect. The acute effects are fairly straightforward to assess, but the chronic effects are tricky because they require monitoring over a long period of time."
Joye should know; her research group has been involved with 19 data-gathering cruises in the Gulf since the spill began, and she's been onboard most of them. The cruises are part of a project called Ecosystem Impacts of Oil and Gas Inputs to the Gulf, or ECOGIG
, that brings together 14 research institutions "to chart the long-term effects and mechanisms of ecosystem recovery from the Macondo blowout." The project is currently funded through 2015, but Joye is hoping to stretch it out a little longer.
"We're looking at a variety of sites around the wellhead and away from the wellhead, and the idea is to monitor these sites over nine years," Joye tells MNN. "Right now we're funded through the next three years, but we hope to extend it. Then we'd have nine years of data, which would put us in a pretty good position to say, 'This is what happened, and this is what's happening to the ecosystem.'"
An array of scientists are still studying the spill's various victims, from microbes and deep-sea coral to fish, shrimp and dolphins. The Deepwater Horizon disaster is already one of the most intensely studied oil spills in history, but its size and complexity — not to mention the X factor of chemical dispersants
— will likely warrant at least a decade of scrutiny. "We still don't know what the long-term consequences of the spill are," Joye says, "with respect to microbiology, fisheries, human health, essentially everything."
For more on what we do know about the worst oil spill in American history, here's a three-year checkup on some of the plants, animals and ecosystems it affected:
The sun sets over a bayou near Larose, La., in July 2010. (Photo: Alex Ogle/AFP/Getty Images)
More than 1,100 miles of shoreline were oiled by the Deepwater Horizon spill in 2010, according to data collected by the National Oceanic and Atmospheric Administration. Earlier this year, the Congressional Research Service estimated
about 340 miles of those beaches and bayous remain "subject to evaluation and/or cleanup operations."
In a new report
for the spill's third anniversary, the National Wildlife Federation argues that "cleaning up oiled wetlands is virtually impossible," since both oil and efforts to remove it can kill coastal plants. As vegetation dies, the loss of roots speeds up erosion and converts land to open water — already a big problem in the Mississippi River Delta. The region has lost about 1,900 square miles of land in the past 80 years, largely due to manmade changes like flood-control levees, reshaped rivers for shipping, and dredged wetlands for oil and gas development. Extracting fossil fuels can also worsen the natural process of land subsidence
, as can invasive species
like nutria that eat native plants.
Without major swamp rehab — possibly funded by BP's federal fines, the NWF points out — Louisiana is projected
to lose another 1,750 square miles by 2060. That's bad for wildlife, but about half of Louisiana's human population also lives in coastal areas less than 3 feet above sea level. And since the Gulf's wetlands are a natural buffer against hurricanes, their demise is especially ill-timed: On top of BP's spill and the threat of others, the Gulf Coast must also deal with rising seas and stronger storms
thanks to climate change.
An oiled pelican tries to fly at Barataria Bay, La., in June 2010. (Photo: Win McNamee/Getty Images)
Pelicans, gulls and other seabirds were some of the most visible victims in the spill's early days. Covered with crude that impeded their ability to swim or fly, they showed up helplessly on beaches and shorelines for months. Volunteers scrubbed their feathers with soap in a race to save them, but federal scientists nonetheless counted 6,147 birds killed by oil in the first year alone, compared with 1,252 that were cleaned and released.
The hardest-hit species was the laughing gull, with 2,981 collected from the spill area between April 2010 and May 2011. Nearly 1,200 of those were visibly oiled, according to the U.S. Fish and Wildlife Service
, and more than 2,700 were already dead or died later.
were No. 2, which was troubling given their history in the region. The birds had just come off the U.S. endangerd species list in 2009, thanks to 40 years of work to reverse their collapse from overhunting and DDT exposure. And while they're no longer on the brink, with thousands now nesting in Louisiana alone, brown pelicans still took a hit from the BP spill. More than 800 were found stranded between April 2010 and May 2011, 40 percent visibly oiled and 70 percent dead or dying. And as the FWS notes, "the number of birds shown may represent only a portion of the total birds affected by the spill."
Still, birds fall into the "acute" class of oil-spill casualties, Joye says. They're mainly affected by thick crude on their feathers or in their stomachs, so the breakdown of oil plumes usually correlates with a drop in deaths. Of course, if oil is still killing wildlife further down the food web, the coast may not be clear for seabirds, either.
An oiled Kemp's ridley sea turtle navigates the Gulf in June 2010. (Photo: Kate Sampson/NMFS)
The Gulf of Mexico has five types of sea turtles, all of which are on the U.S. endangered species list. But one is particularly vulnerable, having invested almost exclusively in the Gulf as a nesting site while its four neighbors enjoy globe-circling ranges. And in a cruel twist of fate, the BP spill killed more of that species than all other turtles combined.
The Kemp's ridley turtle
lives along eastern North America from Mexico to Nova Scotia, and aside from occasional stops in the Carolinas or Florida, it only nests in the Gulf. Less than a year after the spill began, 809 of all known turtle strandings in the region were Kemp's ridleys, according to NOAA
, as were 481 of all known turtle deaths. By comparison, the agency reported 201 green sea turtles (29 dead), 16 hawksbills (none dead), 88 loggerheads (67 dead) and 32 undetermined species (all dead).
About 240 sea turtles are stranded along the U.S. Gulf Coast in a typical year, but more than 1,100 turned up during the BP spill's first 12 months — including 450 visibly oiled and 600 dead or dying. And while the death rate is lower now, it has remained high enough to push the estimated three-year death toll past 1,700. Plus, as with birds, the NWF notes that "only a very small portion of dead sea turtles are ever found."
A pod of striped dolphins swims past a Gulf oil slick on April 29, 2010. (Photo: Ron Wooten/NMFS)
Whales and dolphins in the northern Gulf have been dying in droves for the past three years, leading NOAA to formally declare an Unusual Mortality Event (UME)
. As of April 2013, the UME involves 930 cetacean strandings, 95 percent of which were found dead. The die-off actually started in February 2010, two months before the BP spill, but its length and severity have raised concerns that oil made things worse.
Since NOAA began tracking Gulf UMEs in 1991, it has recorded 12 such events in cetaceans. The top two causes were morbillivirus and marine biotoxins, but NOAA's tests "do not point to these as primary causes of deaths" this time. Thirteen bottlenose dolphins from the current UME have tested positive for Brucella, a bacterium that resembles flu in humans, and scientists are intrigued since it's never been linked to a U.S. dolphin die-off before. Still, those 13 dolphins represent less than a quarter of all dolphins tested, and just 1 percent of the entire UME, so NOAA suspects this is bigger than Brucella.
In Louisiana's heavily oiled Barataria Bay, NOAA reports
many dolphins' symptoms are "consistent with those seen in other mammals exposed to oil," but adds that it's still investigating the cause. "The Barataria Bay dolphins have severe health problems that are not showing up in dolphins from the un-oiled area, and have not been seen in previous studies of dolphins from other sites," NOAA says, noting the animals "are underweight, have low hormone levels, low blood sugar, and some show signs of liver damage."
The Gulf boasts nine dolphin species and a variety of toothed whales, but this UME has hit bottlenose dolphins
the hardest. Some 650 have been stranded so far, including at least 130 infant or stillborn calves. That may be partly due to their wide range of Gulf habitats, but these dolphins have also faced a barrage of environmental hardships lately. As one study
pointed out last year, the spill was compounded by a severe winter, food shortages, bacterial infections and an influx of cold Mississippi River freshwater. "Unfortunately, it was a 'perfect storm' that led to the dolphin deaths," the researchers concluded.
A dead fish lies near Pass Christian, Miss., in May 2010. (Photo: Stan Honda/AFP/Getty Images)
Several fish kills struck the Gulf Coast in the spill's wake, and reports
of fish with open sores, strange black streaks and other deformities have continued years later. Yet linking this to oil has been difficult, and authorities say Gulf seafood is now safe. Fishing bans were lifted in the spill's first year, and many Gulf fisheries are returning to normal.
One fish that isn't back to normal, though, is the western Atlantic bluefin tuna. It was in trouble before the spill due to overfishing, which had cut its population by 82 percent since the 1970s, according to NOAA
, but lately its outlook has been even bleaker. It only spawns in two areas of the northern Gulf, and the BP spill began during its April-May breeding season, oiling about 10 percent
of its spawning habitat. Eggs and larvae are more sensitive to oil than adults, and the spill may have reduced the 2010 crop of bluefin babies by 20 percent, according to the NWF, with a potential 4 percent drop in future populations.
But there is hope for bluefin tuna in the Gulf, thanks in part to new fishing rules. NOAA lowered bluefin quotas
after the oil spill, and also required anglers to use special "weak hooks
" that are less likely to snag bluefin. Still, Joye advises cautious optimism for Gulf fish, citing delayed effects of the 1989 Exxon Valdez oil spill in Alaska. "After the Valdez spill, it didn't become apparent that the herring fishery had collapsed for five years," she says, adding a scientist's caveat that "they're very different ecosystems."
A crab carcass lies near an oiled Mississippi marsh in April 2011. (Photo: Mario Tama/Getty Images)
The black tide washing into Gulf Coast marshes hurt countless shrimp, crabs, copepods and other crustaceans, with juveniles often faring worst. Shrimp losses were especially hard on the region's famous seafood industry, which is rooted in a shrimping culture that dates back more than 200 years. Brown, white and pink shrimp seasons were closed for much of 2010, leading to Louisiana's lowest annual shrimp harvest in decades.
But according to the NWF, shrimp are now one of the few bright spots in the Gulf's recovery. The group rates their status as "good," noting that Louisiana's dismal 2010 shrimping season was followed by a 2011 harvest "commensurate with annual shrimp landings of the past two decades." Despite some lingering reports
of eyeless or otherwise deformed shrimp, the animals now seem relatively stable — good news for wild predators as well as humans, since one year's shrimp harvest can bring more than $100 million to Louisiana alone. Shrimp are still only as healthy as their habitat, however, and the NWF cites the decline of coastal wetlands as a "long-term threat to shrimp."
Oil-eating microbes like these played a key role in the BP oil spill. (Photo: Lawrence Berkeley National Lab)
The smallest actors in the Deepwater Horizon drama may also be among the most important. Joye and other researchers have focused closely on the Gulf's oil-eating bacteria
, which played a key role in the spill by devouring up to 200,000 tons of loose oil. The microbes normally use this ability to get energy from natural oil and gas seeps, which are relatively small, but they swept into action when their habitat was flooded with crude. Joye has been tracking evidence of this, discovering new layers of seafloor sediment created by "marine snow
," or organic debris that sank from the microbes' oily feasts.
In fact, Joye says the broad use of chemical dispersants in 2010 — often credited with preventing larger, thicker blobs of oil from reaching shore — may have been unnecessary, and possibly unwise. The Gulf already has a natural mechanism for breaking down oil, but BP and U.S. officials embraced dispersants like Corexit without controlled experiments to prove their benefit. And according to a study published in December, mixing Corexit with oil can make the oil 52 times more toxic to plankton
At the same time, Joye also cautions against overestimating the bacteria. "I think they've played a very big role in consuming and altering the oil, but they certainly didn't eat it all," she says. "There's still a lot of oil out there in certain places. There tends to be this incorrect assumption that the microbes ate all the oil." While they do get energy from oil, she explains, they can't get nutrients from it. "It's important to keep in mind that if you keep pumping hydrocarbons into the system, you'll eventually overwhelm it."
A brittle starfish clings to dead coral on the Gulf floor in March 2012. (Photo: Charles Fisher/PSU/NSF)
Deep-sea coral colonies grow painfully slowly — a human fingernail grows up to 2,000 times faster — but they can persist for millennia, forming intricate networks along the seabed. This unfortunately put them on the front lines of the BP spill, though, and some of the Gulf's ancient deep-sea reefs were damaged or killed. Surveys conducted shortly after the spill showed a range of responses, with relatively healthy
colonies 12 or more miles away from the wellhead but more signs of distress
closer to the source.
Coral research also supports Joye's skepticism about using dispersants to fight oil spills. One recent study
, for example, exposed two species of coral larvae to a series of mixtures that fell into three categories: oil from the Macondo well, Corexit dispersants and oil mixed with Corexit. Although the responses varied based on species and solution, all three led to lower settlement and survival rates — including Corexit by itself. In fact, exposure to Corexit 9500 resulted in "settlement failure and complete larval mortality" at doses of 50 to 100 parts per million. "I don't think we know nearly enough about the impacts of Corexit," Joye says. "I'm very nervous about using dispersants as a first line of defense in an oil spill, but I worry that's the mentality we're headed toward."
The extent of damage to Gulf coral remains unclear, she adds, arguing it's too soon to know despite "some evidence of recovery." Yet given their growth rates, the NWF warns "recovery of dead and damaged corals to pre-spill conditions could take centuries."
Vacationer Pete Duchock and his daughter, Maddie, survey oil residue from the Deepwater Horizon disaster at Orange Beach, Ala., in June 2010. (Photo: Joe Raedle/Getty Images)
Despite all the damage to wild plants and animals throughout the Gulf, no species was closer to the Deepwater Horizon disaster than humans. Eleven people
died in the initial explosion that destroyed the rig, making it a human tragedy first and foremost.
Thousands upon thousands of people have also been affected in the three years since, and in a wide range of ways. Some were physically sickened by oil or its fumes during the cleanup, while others lost fortunes or entire businesses to prolonged slumps in fishing, shrimping and tourism. BP set up a $20 billion fund
to compensate the spill's myriad victims, of which about $8.2 billion
has been distributed so far. The oil giant must also make amends with Gulf Coast residents in other ways: Last fall, it pleaded guilty to 12 felony charges as part of a $4.5 billion settlement
with the U.S. government, the largest such fine in American history. It also reached a $7.8 billion settlement last spring with private-sector plaintiffs, and a civil trial is currently under way in New Orleans.
Humans' relationship with the spill is complicated, however, by the fact it wouldn't have occurred without us. While it was an accident by all accounts, there is ample evidence it could have been prevented. That was the first conclusion listed by the National Commission on the Deepwater Horizon Oil Spill and Offshore Drilling
, which reported not only that spill was avoidable, but that its causes "can be traced to a series of identifiable mistakes made by BP, Halliburton and Transocean that reveal such systematic failures in risk management that they place in doubt the safety culture of the entire industry."
A BP engineer was arrested
last year for allegedly trying to destroy evidence about the spill, three employees have been charged with manslaughter in connection with the explosion, and an executive has been charged with lying to investigators about how much oil was leaking. The U.S. Justice Department has accused BP of gross negligence
and a "culture of corporate recklessness," but the oil spill commission casts broader blame: "Deepwater energy exploration and production, particularly at the frontiers of experience, involve risks for which neither industry nor government has been adequately prepared."
There's not much anyone can do now to help wildlife overcome the spill, Joye says, aside from keeping a close ecological eye on the northern Gulf. But even if it is too soon to judge the region's recovery, there may still be important lessons to learn in the meantime.
"I think the biggest thing we've learned is the variability in response time," she says. "Some parts of the system seem to be responding pretty quickly and approaching pre-spill conditions, and others are still not functioning correctly." Beyond appreciating the complexity of the Gulf's comeback, Joye also suggests reflecting on our own roles in the disaster. "This entire incident is a call to arms. People need to be aware of the consequences of deepwater drilling and aware of how they use energy," she says. "We all play a critical role in the sustenance of the planet, and we need to be good stewards."
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