VENICE, La. – For birds, fish, sea turtles, marine mammals and ocean-based economies on the Gulf coast, the immediate catastrophe from the BP Deepwater Horizon oil spill has ebbed, but the long-term effects have yet to unfold.
Everything, from shrimp fleets in Louisiana to chicken wings in Buffalo, hinges on the health of tiny plants and animals at risk from oil lingering in the environment. Undetectable by sight or smell, trace amounts of degraded oil are poisoning these species, called plankton, at the bottom of the food chain, scientists say.
The extent of the damage and its implications for the health of the Gulf are unknown and likely will not surface for another year or two.
But the stakes are significant, because plankton provide vital food for shrimp and fish.
For example, plankton feed menhaden, a fish harvested widely in the Mississippi Delta for fishmeal. And fishmeal is a key ingredient in feed for farm-raised catfish, chickens and pigs. That is just one way in which the oil spill’s damage to the Gulf could ripple to dinner tables across the nation.
The spill occurred during spawning season for most fish, shrimp and crab species, an almost certain death sentence for any of their young that encountered oil. Oil on the sea floor, trapped in marshes, buried on sandy beaches and floating in dispersed plumes will continue to kill, deform or sicken a variety of other species, from algae to birds, in varying stages of maturity.
“When you are perturbing the food web from its foundation, the ultimate ecological response could be catastrophic,” said David Hollander, a chemical oceanographer with the University of South Florida’s College of Marine Science.
Hollander and his colleagues at USF are among the first to suggest that plumes containing extremely low concentrations of BP oil are having toxic effects on beneficial algae, a large component of plankton.
Many other scientific teams nationally are trying to grasp the scope of the problem, challenging the perception that the disaster is over.
In some areas of the Gulf, animals searching for food may starve. Others could be forced far afield in their quest for nourishment. And still others could grow weak and susceptible to illness, a factor many scientists believe led to the crash of herring in Prince William Sound four years after the Exxon-Valdez tanker collision that spilled 11 million gallons of oil into the pristine bay.
That disaster may provide a dismal lesson for those analyzing the Gulf spill: Twenty-two years later, oil remains in the environment there. Several species, including herring, have not recovered.
After the explosion of the Deepwater Horizon rig on April 20, 186 million to 227 million gallons of oil gushed into the Gulf of Mexico, about 60 miles south of the Mississippi Delta’s marshlands.
The well was plugged July 15, bringing relief to Gulf communities, especially those on the northern coast. As the surface slick dissipated, cleanup workers started to leave.
But parts of Barataria Bay remain heavily oiled, and as flows from the Mississippi River decline this fall, shrimpers expect to see more oil in the marshes. They fear a total loss of young shrimp this year and a continued toll on the population for years to come.
“They said they picked up 75 percent of oil. They better come back because there’s 75 percent of oil still out there,” said Johnny Bourgeois Sr., standing beside his son’s new shrimp boat at Venice Harbor, where Plaquemines Parish slips into marshland. “This here ain’t going to be cleaned up for 10 to 15 years.”
Where the line between land and water blurs, his fishing roots go back five generations. His 86-year-old Papa is “still running around the bayou” catching shrimp. So are his brother Danny and his brother-in-law James Bemoll.
“They say it’s going to kill the crop. After they lay the eggs it’s going to kill them,” Johnny Jr. said. His boat has been mostly idle since he bought it in May, following a bumper harvest.
Demand for Gulf shrimp has slipped over fears about the safety of seafood, dragging prices down to about half of what they were in the spring, when a pound of medium shrimp brought $2.
“I’m worried about the future, what’s going to happen later,” Bourgeois said. He fears that the adult shrimp this year will not spawn again, a serious problem for a creature with a life span of roughly 12 months. Meanwhile, the small shrimp seem to have disappeared.
“It’s all big shrimp,” Bourgeois said.
‘Chicken bone to marsh bone’
Bob Thomas, director of the Center for Environmental Communication at Loyola University, uses a variation of the old “Dry Bones” song to emphasize the interconnectedness of the Louisiana marshes to food produced far inland.
“The chicken bone is connected to the marsh bone,” he says.
It starts with plankton, a diverse community of tiny, sometimes microscopic, plants and animals. Plankton includes algae, fully grown microscopic animals, and the larvae of crabs, oysters, fish and other sea creatures.
Some fish only eat plankton, including one that ranks as one of the most commercially important fish in the nation.
Gulf menhaden, or pogey as the locals call it, represents the second-largest commercial fishery in the nation by weight, with landings of nearly 470,000 tons annually. More than 90 percent of that catch comes from Louisiana.
Nobody eats menhaden. Instead the small fish are ground into fishmeal, an important protein source for animal feed.
“That’s what they feed the chicken that allows us to have such a big chicken crop in our country,” Thomas said. “It ties together a lot of things you don’t necessarily connect.”
Fish oil from menhaden also goes into supplements, trendy health foods and cosmetics.
So plankton feeds menhanden, menhaden feeds chicken, chicken feeds people. In the Gulf of Mexico, the chain becomes more complex. The plankton feed thousands of different animals that go on to feed hundreds more in a complex dynamic called the food web.
When one element disappears, connections get mixed up.
In Prince William Sound, where the Exxon-Valdez ran aground in 1989, Pacific herring fills the food web role held by menhaden in the Gulf.
The Exxon-Valdez accident occurred during spawning season for herring. A year later, the fish came back in force, bringing a sense of relief.
But herring take four years to become adults. And like clockwork, the herring population of Prince William Sound collapsed four years after the spill.
Those that came back were covered in lesions, ravaged by disease. Scientists still argue over whether the collapse was coincidental or caused by the oil spill.
“The spill was probably one of several factors that caused the collapse,” said Stan Senner, who led restoration planning and helped coordinate research for the state of Alaska and the federal government following the spill. He is now director of conservation science for the Ocean Conservency, an environmental advocacy group.
Since that 1993 collapse, the herring population in Prince William Sound has not recovered and disease still plagues the fish. Birds that rely on the herring have likewise not recovered.
Oil remains buried in Prince William Sound sediments and trapped in the crannies of mussel beds, setting back the recovery of sea otters. Scientists report that the buried oil is just as toxic as nearly 20 years ago.
In the Gulf, menhaden take two years to reach maturity. Red snapper take two to four years, bottlenose dolphins 10 years, sea turtles 35 years.
“A lot of the species that are potentially affected by the spill have very long lives,” Senner said. “We may not see some of the impacts of the spill until much later on.”
All these habitats
The BP spill affected marshes, the deep sea, the sea surface and the mysterious zone between the first few hundred feet of the ocean surface and the dark sea depths.
“The spill occurred just north of what we believe is a primary spawning ground for blue crab and should be a major spawning ground for brown and white shrimp,” said Richard Condrey, associate professor at Louisiana State University’s Department of Oceanography and Coastal Sciences.
The perils crabs face are similar to those of several other ecologically and commercially important species with similar life cycles, Condrey said.
These animals, including shrimp, menhaden, oysters and clams, spend a part of their lives as zooplankton, tiny larvae that float at the whim of ocean currents and gobble other bits of plankton.
The spill coincided with the time of year when those zooplankton drift near the surface of the deep sea. They likely encountered oil and chemical dispersants used to dissolve the oil. If direct exposure did not kill them, they could still suffer reduced immunity to disease or genetic mutations that interfere with their growth into reproductive adults.
Scientists know oil and dispersants are toxic to plankton, so they theorize that diminished food would also take a toll on larval critters that do not get exposed to oil.
They would either starve or not get enough nourishment to reproduce.
“It’s a whole cascading thing of possibilities that end up being a decline in reproductive output,” Condrey said.
Breeding adults also encountered oil in the marshes and — for mobile species — in spawning grounds offshore and near shore. They would be susceptible to some of the same problems as their young.
Larger fish — tuna, wahoo, sharks — are also vulnerable to shifts in the food web, as are marine mammals such as whales and dolphins.
Further, the more tainted food they eat, the more toxins will build up in their bodies.
Far below the surface of the ocean, where sunlight barely penetrates, lampfish, dragonfish and hatchetfish look like creatures from a horror movie, with bulging eyes and ragged teeth. Though they get little attention from the public, they feed large migrating fish that people like to eat, said Joseph Torres, a biological oceanographer at the University of South Florida.
Torres is studying the spill’s effect on fish that dwell in depths ranging from about 500 to 2,500 feet, the same mid-water depths at which scientists discovered tiny oil droplets in cloudlike plumes.
The fish migrate daily to eat zooplankton at night. That vertical migration places them at a great risk for exposure to oil in plumes.
“I’m very concerned that these guys would be encountering the oil at depth and altering their behavior or maybe even killing them,” Torres said.
If the oil does what Torres fears, larger fish that travel in search of food to certain parts of the Gulf during different times of year may starve.
Such ripple effects happen over years.
“It’s important not to take the snapshot or the short-sighted approach, but the long-term view,” said Hollander, the chemical oceanographer working with Torres.
“We don’t have a good handle on how everything works.”