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EMBO Rep >

v.12(1); Jan 2011
>

PMC3024133

EMBO
Rep. 2011 January; 12(1): 27–30.

doi:  10.1038/embor.2010.197

PMCID:
PMC3024133

Science and Society

Feature

Natural healing

How does Nature repair itself after an oil spill?

Melissa
Suran1

1Melissa Suran is a journalist in Chicago, IL,
USA.

Melissa Suran is a journalist in Chicago, IL,
USA.

Author information
► Copyright and License information
►

Copyright ©
2011, European Molecular Biology Organization

Abstract

Few environmental disasters are as indicting of humanity as major oil
spills. Yet Nature has sometimes shown a remarkable ability to clean up the oil
on its own.

In late April 2010, the BP-owned semi-submersible oilrig known as Deepwater
Horizon exploded just off the coast of Louisiana. Over the following 84 days,
the well from which it had been pumping spewed 4.4 million barrels of crude oil
into the Gulf of Mexico, according to the latest independent report (Crone
& Tolstoy, 2010). In August, the US Government released an even grimmer
estimate: according to the federal Flow Rate Technical Group, up to 4.9 million
barrels were excreted during the course of the disaster. Whatever the actual
figure, images from NASA show that around 184.8 million gallons of oil have
darkened the waters just 80 km from the Louisiana coast, where the Mississippi
Delta harbours marshlands and an abundance of biodiversity (NASA Jet
Propulsion Laboratory, 2010; Fig
1).

…the Deepwater incident is not the first time that a massive oil
spill has devastated marine and terrestrial ecosystems, nor is it likely to be
the last

Figure 1

Images of the Deepwater Horizon oil slick in the Gulf of Mexico.
These images were recorded by NASA's Terra spacecraft in May 2010. The image
dimensions are 346 × 258 kilometres and North is toward the top. In the upper
panel, the oil appears ...

The resulting environmental and economic situation in the Gulf is
undoubtedly dreadful—the shrimp-fishing industry has been badly hit, for
example. Yet the Deepwater incident is not the first time that a massive oil
spill has devastated marine and terrestrial ecosystems, nor is it likely to be
the last. In fact, the US National Oceanic and Atmospheric Association (NOAA)
deals with approximately 300 oil spills per year and the Deepwater
catastrophe—despite its extent and the enormous amount of oil released—might not
be as terrible for the environment as was originally feared. Jacqueline Michel,
a geochemist who has worked on almost every major oil spill since the 1970s and
who is a member of NOAA's scientific support team for the Gulf spill, commented
that “the marshes and grass are showing some of the highest progresses of [oil]
degradation because of the wetness.” This rapid degradation is partly due to an
increased number of oil-consuming microbes in the water, whose population growth
in response to the spill is cleaning things up at a relatively fast pace (Hazen et
al, 2010).

It therefore seems that, however bad the damage, Nature's capacity to
repair itself might prevent the unmitigated disaster that many feared on first
sight of the Deepwater spill. As the late social satirist George Carlin
(1937–2008) once put it: “The planet will shake us off like a bad case of fleas,
a surface nuisance[.] The planet will be here for a long, long—LONG—time after
we're gone, and it will heal itself, it will cleanse itself, because that's what
it does, it's a self-correcting system.”

Michel believes that there are times when it is best to leave nature
alone. In such cases the oil will degrade naturally by processes as simple as
exposure to sunlight—which can break it down—or exposure to the air—which
evaporates many of its components. “There have been spills where there was no
response because we knew we were going to cause more harm,” Michel said.
“Although we're going to remove heavier layers of surface oil [in this case],
the decision has been made to leave oil on the beach because we believe it will
degrade in a timescale of months […] through natural processing.”

To predict the rate of general environmental recovery, Michel said one should
examine the area's fauna, the progress of which can be very variable. Species
have different recovery rates and although it takes only weeks or months for
tiny organisms such as plankton to bounce back to their normal population
density, it can take years for larger species such as the endangered sea turtle
to recover.

…however bad the damage, Nature's capacity to repair itself might
prevent the unmitigated disaster that many feared on first
sight…

Kimberly Gray, professor of environmental chemistry and toxicology
at Northwestern University (Evanston, IL, USA), is most concerned about the oil
damaging the bottom of the food chain. “Small hits at the bottom are amplified
as you move up,” she explained. “The most chronic effects will be at the base of
the food chain […] we may see lingering effects with the shrimp population,
which in time may crash. With Deepwater, it's sort of like the straw that broke
the shrimp's back.”

Wetlands in particular are a crucial component of the natural
recovery of ecosystems, as they provide flora that are crucial to the diets of
many organisms. They also provide nesting grounds and protective areas where
fish and other animals find refuge from predation. “Wetlands and marsh systems
are Nature's kidneys and they've been damaged,” Gray said. The problem is
exacerbated because the Louisiana wetlands are already stressed in the aftermath
of Hurricane Katrina, which devastated the Gulf coast in August 2005, and
because of constant human activity and environmental damage. As Gray commented,
“Nature has a very powerful capacity to repair itself, but what's happening in
the modern day is assault after assault.”

Ron Thom, a marine ecologist at Pacific Northwest National
Laboratory—a US government-funded research facility (Richland, WA, USA)—has done
important research on coastal ecosystems. He believes that such habitats are
able to decontaminate themselves to a limited degree because of evolution.
“[Coastal-related ecosystems are] pretty resilient because they've been around a
long time and know how to survive,” he said.

As a result, wetlands can decontaminate themselves of pollutants such as oil,
nitrate and phosphate. However, encountering large amounts of pollutants in a
short period of time can overwhelm the healing process, or even stop it
altogether. “We did some experiments here in the early 90s looking at the
ability for salt marshes to break down oil,” Thom said. “When we put too much
oil on the surface of the marsh it killed everything.” He explained that the oil
also destroyed the sediment–soil column, where plant roots are located.
Eventually, the roots disintegrated and the entire soil core fell apart.
According to Thom, the Louisiana marshes were weakened by sediment and nutrient
starvation, which suggests that the Deepwater spill destroyed below-ground
material in some locations. “You can alter a place through a disturbance so
drastic that it never recovers to what it used to be because things have changed
so much,” he said.

“Nature has a very powerful capacity to repair itself, but what's
happening in the modern day is assault after assault”

Michael Blum, a coastal marsh ecologist at Tulane University in New
Orleans, said that it is hard to determine the long-term effects of the oil
because little is known about the relevant ecotoxicology—the effect of toxic
agents on ecosystems. He has conducted extensive research on how coastal marsh
plants respond to stress: some marshes might be highly susceptible to oil
whereas others could have evolved to deal with natural oil seepage to metabolize
hydrocarbons. In the former, marshes might perish after drastic exposure to oil
leading to major shifts in plant communities. In the latter case, the process of
coping with oil could involve the uptake of pollutants in the oil—known as
polycyclic aromatic hydrocarbons (PAHs)—and their reintroduction into the
environment. “If plants are growing in the polluted sediments and tapping into
those contaminated sources, they can pull that material out of the soil and put
it back into the water column or back into the leaf tissue that is a food source
for other organisms,” Blum explained.

In addition to understanding the responses of various flora,
scientists also need to know how the presence of oil in an ecosystem affects the
fauna. One model that is used to predict the effects of oil on vertebrates is
the killifish; a group of minnows that thrive in the waters of Virginia's
Elizabeth River, where they are continuously exposed to PAHs deposited in the
water by a creosote factory (Meyer
& Di Giulio, 2003). “The killifish have evolved tolerance to the
exposure of PAHs over chronic, long-term conditions,” Blum said. “This suggests
that something similar may occur elsewhere, including in Gulf Coast marshes
exposed to oil.”

Although Michel is optimistic about the potential for environmental
recovery, she pointed out that no two spills are the same. “There are lot of
things we don't know, we never had a spill that had surface release for so long
at this water depth,” she said. Nevertheless, to better predict the long-term
effects, scientists have turned to data from similar incidents.

In 1989, the petroleum tanker Exxon Valdez struck Bligh Reef off the coast of
Prince William Sound in Alaska and poured a minimum of 11 million gallons of oil
into the water—enough to fill 125 Olympic-sized swimming pools. Senior scientist
at NOAA, Stanley Rice of Juno, Alaska, studies the long-term effects of the
spill and the resulting oil-related issues in Prince William Sound. Rice has
worked with the spill since day 3 and, 20 years later, he is seeing major
progress. “I never want to give the impression that we had this devastating oil
spill in 1989 and it's still devastating,” he said. “We have pockets of a few
species where lingering oil hurts their survival, but in terms of looking at the
Sound in its entirety […] it's done a lot of recovery in 20 years.”

…little is known about the relevant ecotoxicology—the effect of
toxic agents on ecosystems

Despite the progress, Rice is still concerned about one group of
otters. The cold temperature of the water in the Sound—rarely above 5 °C—slows
the disintegration of the oil and, every so often, the otters come in contact
with a lingering pocket. When they are searching for food, for example, the
otters often dig into pits containing oil and become contaminated, which damages
their ability to maintain body temperature. As a result, they cannot catch as
much food and starve because they need to consume the equivalent of 25% of their
body weight every day (Rice,
2009).

“Common colds or worse, pneumonia, are extremely debilitating to an
animal that has to work literally 365 days a year, almost 8 to 12 hours a day,”
Rice explained. “If they don't eat enough to sustain themselves, they die of
hyperthermia.” Nevertheless, in just the last two years, Rice has finally seen
the otter population rebound.

Unlike the otters, one pod of orca whales has not been so lucky.
Since it no longer has any reproductive females, the pod will eventually become
extinct. However, as it dies out, orca prey such as seals and otters will have a
better chance of reproducing. “There are always some winners and losers in these
types of events,” Rice said. “Nature is never static.”

The only ‘loser' that Rice is concerned about at the moment is the
herring, as many of their populations have remained damaged for the past 20
years. “Herring are critical to the ecosystem,” he said. “[They are] a base diet
for many species […] Prince William Sound isn't fully recovered until the
herring recover.”

North America is not alone in dealing with oil-spill
disasters—Europe has had plenty of experience too. One of the worst spills
occurred when the oil tanker Prestige leaked around 20 million gallons of oil
into the waters of the Galacian coast in Northern Spain in 2002. This also
affected the coastline of France and is considered Spain's worst ecological
disaster.

“The impacts of the Prestige were indeed severe in comparison with other
spills around the world,” said attorney Xabier Ezeizabarrena, who represented
the Fishermen Guilds of Gipuzkoa in a lawsuit relating to the spill. “Some
incidents aren't even reported, but in the European Union the ratio is at least
one oil spill every six months.”

For disasters involving oil, oceanographic data to monitor and
predict the movement of the spill is essential

In Ezeizabarrena's estimation, Spanish officials did not respond
appropriately to the leak. The government was denounced for towing the shipwreck
further out into the Atlantic Ocean—where it eventually sank—rather than to a
port. “There was a huge lack of measures and tools from the Spanish government
in particular,” Ezeizabarrena said. “[However], there was a huge response from
civil society […] to work together [on restoration efforts].”

Ionan Marigómez, professor of cellular biology at the University of the
Basque Country, Spain, was the principal investigator on a federal
coastal-surveillance programme named Orbankosta. He recorded the effects of the
oil on the Basque coast and was a member of the Basque government's technical
advisory commission for the response to the Prestige spill. He was also chair of
the government's scientific committee. “Unfortunately, most of us scientists
were not prepared to answer questions related to the biological impact of
restoration strategies,” Marigómez said. “We lacked data to support our advice
since continued monitoring is not conducted in the area […] and most of us had
developed our scientific activity with too much focus on each one's particular
area when the problem needed a holistic view.”

…the world consumes approximately 31 billion barrels of oil per
year; more than 700 times the amount that leaked during the Deepwater
spill

For disasters involving oil, oceanographic data to monitor and
predict the movement of the spill is essential. Clean-up efforts were initially
encouraged in Spain, but data provided by coastal-inspection programmes such as
Orbankosta informed the decision to not clean up the Basque shoreline, allowing
the remaining oil debris to disintegrate naturally. In fact, the cleaning
activity that took place in Galicia only extended the oil pollution to the
supralittoral zone—the area of the beach splashed by the high tide, rather than
submerged by it—as well as to local soil deposits. On the Basque coast,
restoration efforts were limited to regions where people were at risk, such as
rocky areas near beaches and marinas.

Eight years later, Galicia still suffers from the after-effects of
the Prestige disaster. Thick subsurface layers of grey sand are found on
beaches, sometimes under sand that seems to be uncontaminated. In Corme-Laxe Bay
and Cies Island in Galicia, PAH levels have decreased. Studies have confirmed,
however, that organisms exposed to the area's sediments had accumulated PAHs in
their bodies. Marigómez, for example, studied the long-term effects of the spill
on mussels. Depending on their location, PAH levels decreased in the sampled
mussel tissue between one and two years after the spill. However, later research
showed that certain sites suffered later increases in the level of PAHs, due to
the remobilization of oil residues (Cajaraville et al, 2006). Indeed, many populations of
macroinvertebrate species—which are the keystones of coastal ecosystems—became
extinct at the most-affected locations, although neighbouring populations
recolonized these areas. The evidence suggests that only time will tell what
will happen to the Galicia ecosystem. The same goes for oil-polluted
environments around the world.

The concern whether nature can recover from oil spills might seem
extreme, considering that oil is a natural product derived from the earth. But
too much of anything can be harmful and oil would remain locked underground
without human efforts to extract it. “As from Paracelsus' aphorism, the dose
makes the poison,” Marigómez said.

According to the US Energy Information Administration, the world
consumes approximately 31 billion barrels of oil per year; more than 700 times
the amount that leaked during the Deepwater spill. Humanity continues, in the
words of some US politicians, to “drill, baby, drill!” On 12 October 2010, less
than a year after the Gulf Coast disaster, US President Barack Obama declared
that he was lifting the ban on deepwater drilling. It appears that George Carlin
got it right again when he satirized a famous American anthem: “America,
America, man sheds his waste on thee, and hides the pines with billboard signs
from sea to oily sea!”

References

Cajaraville MP, Garmendia L, Orbea A, Werding R,
Gómez-Mendikute A, Izagirre U, Soto M, Marigómez I (2006) Signs of recovery of mussels health two years after the
Prestige oil spill. Mar Environ Res
62: 337–341.

Crone TJ, Tolstoy M (2010) Magnitude of
the 2010 Gulf of Mexico oil leak. Science 330: 634. [PubMed]

Hazen T et al. (2010) Deep-sea oil plume
enriches indigenous oil-degrading bacteria. Science 330: 204–208.
[PubMed]

NASA Jet Propulsion Laboratory (2010) NASA satellite views massive Gulf oil spill. www.jpl.nasa.gov/news/news.cfm?release=2010–147.

Meyer JN, Di Giulio RT (2003) Heritable
adaptation and associated fitness costs in killifish (Fundulus
heteroclitus) inhabiting a contaminated estuary. Ecol Appl 13:
490–503.

Rice SD (2009) Persistence, toxicity,
and long-term environmental impact of the Exxon Valdez oil spill. Univ St Thomas Law J 7:
55–67.

Articles from EMBO Reports are provided here
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Organization

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Magnitude
of the 2010 Gulf of Mexico oil leak. [Science.
2010]

Crone TJ, Tolstoy M

Science. 2010 Oct 29;
330(6004):634.

Deep-sea
oil plume enriches indigenous oil-degrading bacteria. [Science. 2010]

Hazen TC, Dubinsky EA, DeSantis TZ, Andersen GL, Piceno YM,
Singh N, Jansson JK, Probst A, Borglin SE, Fortney JL, Stringfellow WT, Bill
M, Conrad ME, Tom LM, Chavarria KL, Alusi TR, Lamendella R, Joyner DC, Spier
C, Baelum J, Auer M, Zemla ML, Chakraborty R, Sonnenthal EL, D'haeseleer P,
Holman HY, Osman S, Lu Z, Van Nostrand JD, Deng Y, Zhou J, Mason OU

Science. 2010 Oct 8;
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