Petroleum Pollution: Deepwater Horizon Oil Spill

By Oliver Oglesby

Origins

Natural Seeps: leaking oil

from rocks below the

seafloor, common in the

Gulf of Mexico.

Extraction: spills from

offshore oil platforms.

Transportation: discharge

from ships at sea as well

as spills from tankers and

pipelines.

Consumption: oil from

boating and jet skis in

coastal waters and runoff

from land; cars drip oil

which is washed away by

rains and eventually end

up in rivers or drains that

lead to the ocean.

Almost 85% of the 29 million gallons that enter North American

annually come from land-based runoff, polluted rivers, and

vehicles, with less than 8% from spills.

Average annual contribution to oil in the ocean (in kilotons)

Oil Drilling

Geologists most commonly locate oil using seismology,

creating shock waves that pass through rock layers then

interpreting waves that are reflected back to the surface.

Mobile offshore drilling units dig the initial well, drilling down

into the seafloor with the riser, allowing drilling fluids to move

between the floor and the rig. The drill string pierces the rock

accompanied by a blowout preventer, which closes off the

pipe leading up to the rig in the case of a blowout. Once the

well bore is sealed, the production rig takes over, using an

electric motor that powers a pump, creating a suction that

draws oil up through the well.

(Yellow and orange rigs are semi-submersibles, the same

type as the Deepwater Horizon, which was quite

advanced)

Oil comes from the remains of

tiny plants and animals (typically

plankton) that died millions of

years ago. They decayed in

mud and sand at the bottom of

the sea, were covered with

sedimentary layers, and intense

heat and pressure distilled the

organic matter into crude oil and

natural gas.

The Explosion (April 20, 2010)

The previous September, the Deepwater

Horizon set a deepwater record when it

drilled just over 35,000 feet at another

BP site in the Gulf of Mexico.

At the time of the explosion it was drilling

a roughly 35,000 feet deep exploratory

well at a water depth of almost 5,000

feet, about 40 miles of the coast of

Louisiana.

The central cause was the failure of

cement at the base of the well, which led

to a series a human and mechanical

errors that allowed high-pressure

methane gas to shoot onto the drilling

platform, causing an explosion that killed

11 and injured 17 of the 126 crew

members.

Efforts to douse the flames by multiple

ships immediately after the explosion

were unsuccessful and the oil platform

sunk after burning for approximately 36

hours.

The Spill After the blowout, between 53,000 and 62,000

barrels (2.2 and 2.6 million gallons) per day leaked

from the well, and over the course of 86 days it

poured an estimated 4.9 million barrels (more than

200 million gallons) into the Gulf of Mexico.

Initial oil mitigation efforts proved futile as attempts

to cap the wellhead stem the flow of petroleum

failed.

On July 15 the well was effectively sealed as a

better-fitting cap was planted and reinforced with

mud and cement, providing a temporary stop to

the oil flow. After relief wells were drilled, the

Deepwater Horizon was declared dead on

September 19, 2010.

By June, President Obama had proclaimed it the

worst environmental disaster ever faced in the

America. It had not only become the largest oil

spill in United States’ history, but the largest

accidental spill in the history of the petroleum

industry.

Response Efforts By April 29, 69 vessels were active in cleanup

efforts, with an estimated 170 five days later,

aided by 7,500 personnel and an additional

2,000 volunteers.

At this time, 100,000 feet of containment boom

had been deployed, to corral the oil and block it

from, or at least minimize impact to, marshes,

mangroves, oyster ranches and other

ecologically sensitive areas, which was

somewhat successful.

Gulf Coast Government officials released water

through Mississippi River diversions, in a

desperate measure calling upon water from the

entire Mississippi Watershed (which covers

nearly 40% of the landmass of the continental

United States), to create an outflow of water that

would keep the oil off the coast, which was

marginally effective.

In the long run, oil was removed through filtering

offshore, collecting for later processing, and

most commonly by burning the petroleum (bad

for the atmosphere).

Dispersants

Although spilled oil naturally disperses

through storms, currents, and osmosis

as time passes, in order to accelerate

the cleansing process, chemical

dispersants were used (chiefly Corexit

EC9500A and Corexit EC9527A).

Dispersants are harmful to marine

organisms, especially fish eggs and

larvae, though “while toxic, [they] are

much less toxic than oil. Using them on

an oil spill produces the ‘lesser of two

difficult environmental outcomes,’ says

EPA administrator Lisa Jackson.”

The chemicals bond to the oil

molecules and separate them from

water molecules, thus breaking up the

petroleum; ultimately it results in tiny oil

droplets that can biodegrade faster

than a mass of oil.

Dispersants are usually used on the surface of the

ocean, distributed by aircraft flying over the spill; BP

had already made 120 such flights less than a month

after the disaster.

Cleanup authorities also decided to use “the first

subsea injection of dispersant directly into oil at the

source”which, although more detrimental to the

marine environment, could help break up and

disperse the oil before it reached the surface.

Extent • The spill was estimated to be over 130 miles long and 70 miles wide by June, having reached the

shores of Louisiana, Mississippi, Alabama, and Florida, the heart of the Mississippi River Delta region.

April 28 May 28

June 28 July 28

Economic Impact

On April 29, an emergency shrimping season was opened

so that a catch could be brought in before the oil advanced

too far.

Commercial fisheries made over

659 million dollars in 2008 and

just over three million people

took recreational fishing trips in

the Gulf that year. After the spill,

recreational fishing from the

Atchafalaya Delta to Mobile Bay

was shut down from May to

August and state park closures

caused a serious blow to their

summer revenue; a mere

example of the devastation

faced by the fishing and tourism

industries as well as numerous

other businesses across the

region.

Ecological Impact:

Abiotic Factors -

Biodegradation While crude oil primarily consists of

hydrocarbons (chemicals made of

hydrogen and carbon), it also contains

hundreds of substances that include

benzene, chromium, iron, mercury,

nickel, nitrogen, oxygen, sulfur, toluene,

and xylene, many of which are toxic.

Oil plumes limited light from reaching

greater depths and organisms on the

seafloor.

Abiotic factors influenced the

biodegradation of the oil, the process of

chemically braking down organic

material by microbes and invertebrates,

particularly bacteria in saltwater

environments.

(continued)...

Ecological Impact:

Abiotic Factors -

Biodegradation (...continued)

Temperature: colder = slower rate of biodegradation; warmer = faster rate of biodegradation,

(applicable to the warmer Gulf of Mexico).

At the wellhead of the Deepwater Horizon the temperature was about 40 degrees Fahrenheit,

taking several days for the hydrocarbons to biodegrade or disappear.

Dissolved Oxygen: in open water, oil hydrocarbons undergo biodegradation by bacteria that use

oxygen dissolved in the water.

Scientists found dissolved oxygen levels to be at a rate of 30 percent depletion around the

spill, which demonstrated the presence of biodegrading microbes.

Location: Hydrocarbons that settle into sediments on the ocean floor and along coasts undergo a

fast form of biodegradation, while oil onshore lingers longer and can become a chronic pollutant.

Fortunately, “The Gulf spill released light, sweet crude oil, which is more readily broken down

than heavy, sour oil.” The use of chemical dispersants also quickened the process.

Ecological Impact:

Biotic Factors - Planktonic

The mixture of crude oil and Corexit (chemical dispersants) proved to be more toxic than oil

alone, but largely the population did not experience any major setbacks.

Individual phytoplankton species experienced mortality or enhanced growth (depending on the

species).

“While studies of the Deepwater Horizon Oil Spill will continue to provide new information in the

coming months and years, early research shows that the planktonic community exhibits an

encouraging level of resilience.”

Scientists believe this is a result of local adaptations to natural oil seeps, in addition to their

general diversity and specialization. This is also attributed to oil dispersion, high reproduction

rates, decreased predation, and an ability to avoid direct contact with oil.

Only 60 days after the blowout, planktonic communities returned to their normal levels but even

still “A boom-and-bust cycle of bacterial succession is common, though not certain, after oiling

events.”

Ecological Impact:

Biotic Factors - Fish

When exposed to oil, adult

fish may develop enlarged

livers, changes in heart

and respiration rates, fin

erosion, reproduction

impairment, and overall

reduced growth.

Petroleum has more

dramatic effects on eggs

and larvae survival.

From April through June, the Gulf serves as the sole breeding ground for western Atlantic

bluefin tuna, a both commercially important and endangered species. Deformities have been

found in tuna larvae and scientists have noted that the “Atlantic bluefin tuna would likely suffer

significant mortality with direct oil contact, but secondary effects such as an increase in food

supply are still to be determined.”

Ecological Impact:

Biotic Factors - Larger Organisms

Oil destroys the insulating ability of

fur-bearing mammals, such as seals,

and the water-repelling abilities of a

bird's feathers, thus exposing these

animals to harsh elements as many

die from hypothermia.

Suffering from the cold was not much

of an issue in the Gulf of Mexico but

in the months immediately following

the disaster birds were found with oil-

coated feathers, causing them to lose

their buoyancy and ability to regulate

body temperature, as well as marine

mammals who had ingested oil,

causing ulcers and internal bleeding.

Sea turtles were also found soaked in

oil.

Dead and dying deep sea corals were discovered

seven miles from the Deepwater Horizon well.

In the six months after the spill, more than 8,000

birds, sea turtles, and marine mammals were found

injured or dead.

Related Legislation The Oil Pollution Act of 1990, has established a system for federal and state agencies and the

party responsible for the spill to cooperate and restore the affected area to its original state

before the incident. However, the legislation also limited BP’s liability for non-cleanup costs to 75

million dollars unless gross negligence is proven; but fortunately, BP said it would pay for all

remediation costs in spite of the statutory liability cap.

On February 15, 2012, the House passed H.R. 3408, known as the PIONEERS Act or the

RESTORE Act, dedicating 80% of the Clean Water Act penalties that will be paid as a result of

the Deepwater Horizon oil spill to the Gulf Coast states for environmental and economic

restoration “The money will be used to rebuild wetlands, implement federal plans for coastal

restoration and advance important resiliency measures in Gulf Coast communities,” which would

simultaneously provide numerous economic benefits.

Surprisingly, proposals encouraging offshore oil exploration and development have seen more

legislative action than those oil spill-related.

One bill passed on December 23, 2011, P.L. 112-74 or the Consolidated Appropriations Act,

transfers air emissions regulatory authority off Alaska’s north coast from the Environmental

Protection Agency (EPA) to the Department of the Interior (DOI). The EPA prioritizes air

quality as opposed to offshore energy development supported by the DOI.

Also in 2011, Secretary Salazar of the Department of the Interior initiated a series of reforms

replacing the former regulatory agency, the Minerals Management Service, by reassigning the

functions of the offshore energy program to more environmentally-conscious organizations, a

pleasant sign of improved regulations given the magnitude of the Deepwater Horizon disaster.

Long-term Effects

While the long-term effects of the spill are still being assessed and the full extent of the damage

may not be known for years, many scientists expected it to irreversibly alter the Gulf Coast

ecosystem. “Though oil is no longer readily visible on the surface, it isn’t gone. Scientists have

found significant amounts on the Gulf floor, and the oil that has already washed into wetlands

and beaches will likely persist for years.”

An unbalanced food web will be one of the premier ecological repercussions seeing as the

disaster hit at the peak of breeding season for many marine species.

The oil’s toxicity may have hit egg and larval organisms immediately, diminishing or even

potentially wiping out those age classes.

Without these generations, population dips and cascading food web repurcussions will likely

occur.

“But despite the size of the spill, ‘the natural recovery is far greater than what anybody hoped

when it happened,’ said James Morris, a professor of biology at the University of South Carolina.

‘The fears of most people––that there would be a catastrophic collapse of the ecosystem in the

Gulf––never materialized.’ ”

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