Feature: Five years after the Deepwater Horizon disaster, scars linger
Feature: Five years after the Deepwater Horizon disaster, scars linger
BARATARIA BAY, LOUISIANA—The scene of one of the nation's most dramatic environmental disasters is serene now. Waist-tall marsh grasses shiver in the wind, the tan and green carpet stretching to a hazy blue horizon. The quiet is broken only by small waves clapping a rhythm on the metal hull of a skiff, beached at the edge of the latte-colored Gulf of Mexico. At first glance, it's hard to see anything amiss.
But Linda Hooper-Bui kneels in a patch of grass, pulls up a clod of jet-black earth, and holds it to her nose. “Ooh, smell that, baby,” exclaims the entomologist. A sniff delivers a swift kick reminiscent of motor oil.
Nearly 5 years after BP's Deepwater Horizon oil rig exploded on 20 April 2010, killing 11 workers and unleashing an 87-day undersea geyser of oil that spewed at least 518 million liters, the disaster's legacy is still evident here—if you dig. Barataria Bay, a pocket of islands, inlets, and bayous, endured some of the heaviest oiling, creating scenes of devastation replayed endlessly on screens around the globe. And the bay quickly became a magnet for researchers like Hooper-Bui, who are seeking to understand the spill's impacts.
Today, the scientists are finding both damage and remarkable resilience. The oil has clearly left its mark on the ecosystem, affecting organisms small and large, from soil microbes to bottlenose dolphins. But nature has bounced back in surprising ways. Shrimp scavenge the sea floor. Brown pelicans wheel overhead. Barataria Bay hasn't gone to hell afterDeepwater. But it's not the Garden of Eden, either.
Nicole R. Fuller
A web of impacts
Louisiana's Barataria Bay was one of the places hardest hit by the Deepwater Horizonspill. Five years later, researchers are still studying its impact. Among their findings so far:
- Oil-eating bacteria increased; may have helped accelerate marsh erosion
- Acrobat ants (Crematogaster pilosa) disappeared from oiled sites; may be recovering along with other insects
- There are fewer snails (Littoraria irrorata) in oiled sites; some signs of recovery
- Where oil killed plant roots, erosion increased; mixed evidence of recovery
- Seaside sparrows (Ammodramus maritimus) build fewer nests and hatch fewer chicks in oiled areas; no clear population impact
- Blue crabs (Callinectes sapidus) have shown no signs of population decline; studies continue
- Microflora and fauna, including algae and invertebrates, have mostly recovered; some populations remain low
- Shrimp populations initially increased in oiled estuaries; not clear why
- Larval oysters (Crassostrea virginica) may be more likely to survive and grow faster in unoiled areas
- Oil may have killed thousands of brown pelicans (Pelecanus occidenatlis) Gulf-wide; no clear lasting impact
- Bottlenose dolphins (Tursiops truncatus) are less healthy than Florida dolphins not affected by the spill
- Gulf killifish (Fundulus grandis) show genetic evidence of exposure to toxic chemicals; no obvious population change
The story, however, isn't over. After 5 years, researchers remain uncertain about whether this biological tapestry, frayed by oil, might still unravel in unexpected ways. And the concerns aren't just ecological: What the scientists learn could affect billions of dollars in environmental fines and the livelihoods of thousands of Gulf Coast families.
IN LATE MAY 2010, the oil barged into Barataria Bay like a drunken brawler, pouring through narrow gaps in nearby barrier islands, then lurching back and forth with the tides, currents, and winds. It left some areas untouched. Others, like the shoreline of Bay Jimmy, were coated in muck ranging in consistency from peanut butter to mousse. Many of the disaster's most heart-rending images came from that area—pelicans staring out through a coating of brown goo, a dolphin surfacing in an oil slick, the carcass of an oil-bathed turtle. In the end, 675 kilometers of Louisiana marsh were oiled.
Scientists were soon on the scene, making the most of what amounted to the largest uncontrolled experiment of their lives. Hooper-Bui, for example, left her lab at Louisiana State University (LSU), Baton Rouge, to set up study plots in oiled and unoiled marsh, hoping to chart the fate of ants (her specialty) and other insects. The underlying question: What happens when you take a coastal marsh ecosystem and dunk it in oil?
© BRYAN TARNOWSKI
Linda Hooper-Bui looks for signs of life on Cat Island in Barataria Bay.
Now she is back at the marsh to offer some answers—and to discuss some mysteries that are still stumping scientists. Take the case of the shrunken ant heads. Hooper-Bui chooses a patch of dry grass and starts examining the stalks. Decked out in waders, a camouflage jacket, and a bright pink hood, she's a diminutive dynamo, peppering her scientific patter with exclamations and jokes. (At one point, she holds up an abandoned foam float used to mark crab traps: “What's this?” she asks. “A Bui with a buoy!”)
Eventually, a colleague hands her what she is seeking: a stem with a single, tiny black and red ant scurrying along the outside. Hooper-Bui gently peels open the hollow stalk to reveal a swarm of acrobat ants, named for the way they point their abdomens in the air when pestered. The ants, which typically prey on other insects, live in the dry stems, in colonies 1 to 2 meters across.
In the years after the spill, the ants essentially disappeared from Hooper-Bui's oiled study sites. New colonies got started each spring but vanished by the end of summer. Measurements of the ants' bodies yielded a clue: Those in the oiled areas had smaller heads, a sure sign of malnourishment.
Hooper-Bui has documented a decline of other insects on oiled sites, and experiments with caged katydids left in the marsh suggest the insects are killed by substances released by buried oil. In summer during low tides, the heat can crack the old oil caked on the marsh surface and let relatively fresh oil ooze up. The fumes might be killing insects that the ants like to eat, or keeping the ants from leaving their grass stems to look for food, something Hooper-Bui has observed in lab tests. “They'd rather starve to death when there's oil present,” she says.
So, as the ants swarm onto her hand in early 2015, Hooper-Bui is thrilled. “This is the first time we've seen the ants start to come back and stay [in an oiled area]. … It's very exciting.” The finding fits with signs of an uptick Hooper-Bui started seeing last year. In places hit by the spill, ant colonies had climbed back to 10% of normal, and other insect numbers were higher, too. “We're cautiously saying that there might be recovery,” she says.
THE INSECTS ARE AMONG the clearest examples that the spill is still an ecological force. But there are others. At the marsh's edge, clumps of marsh grass hang in midair over the water, their pale roots suspended where the soil below has washed away.
Marsh erosion was one of the biggest threats to the bay even before the spill. Channels dug by the oil industry have chopped up the marsh, exposing more of it to erosion and killing vegetation by altering water flow patterns. Flood control projects along the Mississippi River starve the bay of fresh sediment from upstream. But soon after the spill, scientists watched erosion go into overdrive. It doubled in some areas, one study found, because oil killed the vegetation that held marsh muck in place. Over the next year and a half, as vegetation grew back on the remaining dirt, erosion rates subsided.
However, the oil may continue to boost erosion by weakening plant roots or by altering bacteria populations deep in the soil, according to a separate study. Oil acts like a fertilizer, fueling a boom in carbon-eating microbes that feast on the petroleum. Those same bacteria can eat away at the layer of rich organic matter that helps bind the marsh together, says Eugene Turner, a colleague of Hooper-Bui's at LSU and a leading expert on the decline of Louisiana's wetlands. Turner found that erosion in some oiled areas started accelerating several years after the spill and that it appears tied to the weakening of this deep layer. He estimates the spill has led to the loss of up to 5 square kilometers of coastal wetlands in Louisiana.
Witnessed firsthand, the pace of erosion in Barataria Bay—whatever the cause—is startling. Five years ago, researchers placed plastic poles along the marsh's shoreline, to mark places hit by oil. Today, the poles stand 20 meters offshore, surrounded by water.
PAST THE POLES, out in the open water, live some of the oil's more photogenic victims: Barataria Bay's bottlenose dolphins. Roughly 1800 of the mammals live in the bay, feasting on fish and shrimp. In 2011, a checkup of 29 dolphins found serious problems associated with oil toxicity: nearly a third had moderate to severe lung disease, many suffered from suppressed hormone levels, and a quarter were severely underweight. Overall, it was a much worse report card than for similar dolphins in Florida, untouched by the spill.
New research suggests a link between the oil and a rash of dolphin deaths. An unusual cluster of at least 128 strandings occurred in the bay between August 2010 and the end of 2011. It's part of a Gulf-wide pattern that started shortly before the spill and continues today, adding up to more than 1250 deaths. Some of the strandings happened prior to the spill, researchers say. But a February study in PLOS ONE by government and private scientists identified a surge of strandings exactly where the spill hit hardest, in Barataria and coastal areas of Mississippi and Alabama.
“The cumulative evidence to date supports that the Deepwater Horizon oil spill is a causal factor for poor dolphin health and increased mortality,” says Lori Schwacke of the National Oceanic and Atmospheric Administration in Charleston, South Carolina, who is helping lead that agency's investigation of how the spill affected dolphins.
The blowout also left a big, but largely unseen, stain on the bottom of the Gulf. Oil sank to the sea floor over more than 3200 square kilometers—an area roughly the size of Rhode Island—according to one study. Near the wellhead, scientists found patches of coral apparently killed or damaged by the oil. As much as 17 kilometers from the center of the spill, the pollution seems to have upended the structure of seafloor communities of small creatures such as worms, tiny crustaceans, snails, and clams, reducing their diversity.
OTHER PARTS of Barataria Bay's ecosystem have proved startlingly resilient. Brown pelicans were a poster child of the oil spill's horrors, for instance, but there's no sign the population as a whole has fallen. Shrimp numbers in the bay actually rose the year after the spill. Researchers don't know if that was because state officials barred fishing for a time, or because the oil somehow caused shrimp to grow more slowly and linger in shallow water, boosting the counts. The bay's seaside sparrows, which nest in grasses, had fewer and less productive nests in oiled areas, according to one study. Yet that doesn't appear to have translated into a drop in overall numbers in the region. In short, there's no sign the spill pushed the bay off some kind of ecological cliff.
(TOP TO BOTTOM) © BRYAN TARNOWSKI; © JOEL SARTORE/NATIONAL GEOGRAPHIC CREATIVE/CORBIS
Thousands of brown pelicans may have died after the oil hit (above), but populations along the Gulf Coast appear to be healthy today (top).
Perhaps most puzzling is the state of the fish, which show clear signs of toxic exposure yet appear to be flourishing. In hard-hit waters, common minnows called Gulf killifish carried genetic markers associated with growth abnormalities, stress, gill damage, and heightened immune response for up to a year after the spill. Scientists have found no evidence, however, that these apparent physiological changes have caused fish numbers to drop in Louisiana's estuaries. They're left with unanswered questions. Has there really been no change? Is any change so subtle it hasn't been detected yet? Or is it too soon to know?
To Ed Overton, an LSU chemist who has spent years tracking the chemical changes in theDeepwater oil that washed ashore, the overall message is upbeat—even though he's found toxic chemicals in the oil that could persist in the bay for years. “I think the big story is, it's remarkable how Mother Nature can cure herself,” he says. “It's really hard to find permanent impacts. Now folks down in the deep water might say ‘Oh we had some impacts down there.’ But those impacts were confined to a pretty small area.”
Others aren't so sanguine.
Some point to the cautionary tale of the herring in Alaska's Prince William Sound. In 1993, 4 years after the Exxon Valdez ran aground in the sound and dumped 42 million liters of oil into the frigid waters, the herring population there crashed. It took another decade before several scientists concluded the fish's decline had actually started in 1989 and was likely tied to the spill.
The take-home message may be that “different components of the ecosystem have very different responses to oiling,” says ecologist Brian Silliman of Duke University's Marine Lab in Beaufort, North Carolina, who specializes in saltwater marshes and studied erosion in Barataria Bay. “Some people say it's resilient and back to normal. But that's just one component of the ecosystem. When is it all back to normal?”
THAT ISN'T JUST a scientific question. At stake are billions of dollars, with repercussions in courtrooms, corporate boardrooms, and local businesses that rely on the Gulf.
G. GRULLÓN/SCIENCE
Eventually—perhaps by 2016—BP and the other companies blamed for the spill are likely to be handed a very big bill for the environmental damage. They've already paid huge economic damage settlements and criminal and civil fines, with more to come (see "Critics question plans to spray dispersant in future deep spills"). But another potentially huge bill is still being tallied by federal and state agencies. It involves completing what is known as the Natural Resource Damage Assessment (NRDA), and NRDA's final price tag will hinge on what scientists say the spill did to the environment and how long the damage lasted. (BP has already made a voluntary down payment of $1 billion for its NRDA bill.)
It's possible government scientists have already arrived at some answers that they aren't making public. Some research is being kept secret for now, because the NRDA findings could wind up in court. For example, the Louisiana Department of Wildlife and Fisheries declined to discuss whether it has seen changes in lucrative species such as oysters, shrimp, or blue crabs.
In the meantime, BP is mounting a publicity campaign declaring the Gulf is largely back to normal. Citing studies that found much of the oil has decomposed and few signs of a drop in wildlife numbers, in mid-March the company issued a lengthy report laying out its case. “[T]he most dire predictions made after the spill did not come to pass,” said Laura Folse, BP's executive vice president for response and environmental restoration, in a statement. “The Gulf is showing strong signs of environmental recovery.”
Those claims have drawn swift responses from Gulf state and federal officials working on the damage assessment. “If you're BP, you're absolutely making the case that you've taken care of things, you've gotten things cleaned up, and you're very much going to say things have come back, things look good,” says Kyle Graham, executive director of Louisiana's Coastal Protection and Restoration Authority in Baton Rouge. “We're going to take probably a slower, more methodical approach to truly assessing what that injury looks like.”
Amid the sniping, locals are sometimes left to draw their own conclusions about what exactly the oil spill did to the bay and whether it will recover.
Pete Vujnovich recently sat in the cramped cabin of his oyster boat, the Miss Eva, in a marina near the little town of Port Sulphur, chain-smoking Marlboro 100's and pondering the state of the Barataria Bay oyster fishery. As a third-generation oysterman, he's come to understand the fickleness of his crop. Salinity, water temperature, and parasites all influence how many oysters he hauls off the mounds of rock and oyster shells dumped on the bottom of the bay to form artificial reefs. “We've had peaks and valleys of production,” he says. But recent years have seen “one of the lowest lows.”
After the spill, he bought rock and shell for replenishing some of his reefs with money from a compensation fund set up by BP. Those areas seem to be doing well. But older reefs are much less fertile than they were before, he says. Overall, he estimates his haul is still 20% below what it was before the spill. “That's the million-dollar question. Was it the oil?” he asks.
Scientists don't have an answer for him. In 2012 and 2013, researchers put cages of oysters in the bay, some in places with oil, others in places that had dodged the spill, to see how mature oysters fared. They didn't find a difference. There were more intriguing findings when they put out blank ceramic and concrete tiles and watched how many baby oysters settled on them. In 2013, fewer settled on the oil-zone tiles. Those that did colonize the tiles grew more slowly in spots where, in addition to oil, they faced a second stressor: low water salinity. That suggests the spill might have compounded the effects of stressful conditions.
It's possible the spill will never yield some secrets. At Bay Jimmy, Hooper-Bui picks up a black, Frisbee-sized chunk of what looks like asphalt mixed with rubber. This slab of fossilized spill, several centimeters thick, is one of the most visible mementos of that long-stanched gusher of crude at the bottom of the Gulf. The ground along the marsh's edge here is paved with the stuff.
© BRYAN TARNOWSKI
A chunk of the solidified oil from the Deepwater spill now provides shelter to small crabs.
Yet marsh grass is growing through it. And as Hooper-Bui flips over the chunk of dried tar, she reveals two small brown crabs clinging to the underside. It's impossible to see what's going on in the crabs' tiny bodies—whether their cells bear damage caused by the oil that they call home, or whether they have found some way to survive, even thrive, in such intimacy with the Deepwater Horizon's legacy.
Warren Cornwall is a freelance writer in Bellingham, Washington.
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