Tankers and cargo ships that carry
oil to be refined and processed are under constant scrutiny by the public and
the government when it comes to environmental concerns. Regulations are put in
place to ensure the safety of the crew on board as well as the protection of
marine environments and ecosystems. Although crude oil transportation, on
paper, should operate smoothly it has occurred to such a large extent that
stricter regulations and clean up protocol are needed to ensure the ecological safety
and future of fisheries, marine biodiversity and to protect against unnecessary
pollution. Figure 1.
oil spills might not pose an immediate threat to humans on land, it should be
of great concern to those who seek the protection of the resources available
and the environment and the long term affects associated with them.
Oil is immiscible in seawater and
forms an emulsion which causes broken up oil droplets to be suspended in the
water column. The oil-water emulsion poses a myriad of concerns for ocean water
chemistry. Understanding the economic, environmental and biochemical impacts of
small scale spills and large scale-media present spills, like those of the
Deepwater Horizon spill or the Exxon Valdez spill, are of great necessity. The
detrimental effects to marine wildlife is popular knowledge to most of the
public and images of water fowl coated in thick layers of crude oil circulate
on television; yet the issues are still occurring and clean up efforts remain
expensive and time consuming and at a cost, ultimately, to the affected
ecosystems and its inhabitants. Understanding that the issue of oil spill
disasters are much more than birds stuck in oil slicks or animals who are
unable open their eyes or swallow because of the entrapped oil on their
membranes, requires that scientists, and most importantly the government and
public, become educated on the effects that oil has on marine fauna. While
prevention and clean up become the concern for oil companies and the
government, understanding the side effects of oil spills on fisheries and the
ecosystem becomes the concern, and responsibility, of the scientist and the
In an endeavor to synthesize data
collected from peer-reviewed journals and government protocol articles, the
effects of oil emulsions, as a result from oil tanker spills, with regards to
water chemistry and biota, will be examined. Oil spill assessment and removal
at sea and along the coast, as well as long term ecological effects will be
taken into account.
Chemical Evaluation of
Oil Spills are quite common, although
not always presented in the media, but only make up a lesser amount of marine
oil pollution. It becomes the responsibility of the company, and associating
scientists, to assess the impact of the spill to determine any short and long
term affects to the water column and biota present. Before the Exxon Valdez
spill information available for the construction of in lab risk-assessment
models were limited. These risk-assessment models are necessary to predict the
ecological impact of oil spills along the coast and offshore. With a staggering
42 million gallons of crude oil spilled along 2000km of pristine shoreline in
the Gulf of Alaska, the Exxon Valdez spill is surprisingly not the greatest oil
spill in recorded history Figure 2.
spill called for a reform in model predictions clean up assessment and protocol
and proved to be beneficial as a small scale spill in assessment: economically,
chemically and biochemically.
Following the Exxon Valdez oil spill,
which occurred off the coast of Alaska in 1989, comprehensive water-quality
assessment tests were preformed on more than 5000 water samples to obtain a
more complete understanding of oil’s interaction with seawater following the
spill. The water samples collected were from offshore locations: areas through
which the oil had spilled, drifted and was adjacent to (regions of water that
were within close proximity to the spill but were believed to be unaffected).
The collected samples were run through sensitive chromatographic evaluations,
which were used to determine the concentrations of polycyclic aromatic
hydrocarbons (PAHs) (Wells et al, 1995).
Scientific literature and medical reports have shown that PAH’s are carcinogens
and act as endocrine disrupters. This poses major threats and health concerns
to fisheries and marine biology. This should be of great concern, and is, to
the scientific and public community as these chemicals are spilled in large
quantities and can remain suspended, even if in considered low concentrations, for
extended periods of time in the water column. The concentrations of total PAHs from
the toxicological reports were used to determine the relative toxicity of the
water and the harm and any associated risks that were posed to marine
organisms. Scientists tested the water samples collected shortly after the
spill (about a week’s time) to determine the concentration and distribution of
the hydrocarbons present within the water column. The examinations were followed
up with toxicity evaluations, which were then compared to the known PAH
sensitivity levels of locally established organisms. The test results of the
chromatographic evaluations preformed by Exxon showed that the measured PAH
levels were “well below” Alaska’s water quality standard of 10ppb total
aromatic hydrocarbons; furthermore, they showed a standard of consistency when
compared against tests run by the National Oceanic and Atmospheric
Administration (NOAA) who collected water samples from the affected region
during the same period of time (Wells et al, 1995). With regards to water
quality standards set in place by the Alaskan government and according to
scientific literature already set in place, the measured concentration of PAHs in
the water samples collected showed that the oil spill posed little to no threat
to the ecosystem and any organisms present, including both marine animals and
plants. These findings, however, only take into account immediate organism mortality
due to PAH toxicity and failed to preform any follow up examinations to gather findings
on possibly lingering long term side affects on long lived organisms (those of
several years) or across generations. These tests would have showed if
hydrocarbons that lingered in the water caused delayed side effects or
generational birth defects.
Effects on Biota and Biotic
spills have detrimental affects on marine populations due to PAHs’ physical and
chemical characteristics. Polycyclic Aromatic Hydrocarbons are carcinogenic and
endocrine disrupters leading to high mortality rates soon after the spill.
Crude oil’s physical properties can leave water fowl and other organisms coated
in a thick layer of grease preventing sight, proper respiration and feeding. The
methods used to remove the oil slicks can also harm organisms significantly,
making clean up a necessary evil and one to be considered. It is only through
careful assessment and understanding that a model and plan of action be carried
out to remove the oil efficiently and effectively.
Oil’s poisonous properties can lead
to problems as a result of inhalation or ingestion, and external exposure,
which can lead to membrane and eye irritation. The oil, as it is popularly
shown on television commercials, can smother small fish, birds and other
aquatic wildlife. This reduces the organism’s ability to feed, breathe and
regulate body temperature. A large number of immediate deaths following an oil
spill are from organisms being coated in oil and dying from hypothermia due to
lack of heat regulation. Since most PAHs float on the surface water and all are
immiscible in water organisms, such as sea otters and water fowl, become the
immediate concern. Large numbers of sea birds have been recorded smothered and
dead from the oil. Figure 3.
the oil breaks up into the water column, and as it comes to shore, other marine
organisms, such as snails and clams, become targets.
It is important to distinguish
between the two types of oil that can be spilled. Different chemical and
physical properties lead to varying resonance times in the environment
depending on if an oil is considered “light” or “heavy”. Lighter oils, such as
those used for fuel like gasoline and diesel, are much more volatile that
heavier oils. These oils are able to evaporate fairly quickly because of their
volatility and can leave the environment within several days. An increase in
surface area due to a spill will decrease the resonance time further. These
lighter oils, however, pose severe immediate risks as they are quite flammable
and are considered toxic. Even to humans, inhalation and external skin exposure
to fuel oils can cause health problems and death to affected organisms.
“Heavy” oils, such as bunker oil
used to fuel cargo ships and vessels, are considerably more viscous, darker in
color and can remain sticky for extended periods of time. If not removed heavy
oils have a longer resonance time (months up to years) in the environment and
can persist without much degradation. Heavy oils pose significantly less toxicity
issues, with respect to the carcinogenic lighter oils, to organisms and are
instead concern for hypothermia due to lack of temperature regulation. As the
thick sticky oil coats the organism, the organism loose the functional ability
to regulate its body heat and can die quickly. Reports have also shown long
term exposure can lead to tumor growth in some species.
Often overlooked, especially by the
public, are the dynamics of the plankton population—including phytoplankton,
zooplankton, marine bacteria and fish larvae—and their ecological responses to
oil spills (Abbriano et al, 2011). Being subject to the currents, fish larvae
are of extreme importance to commercial fisheries, notably the Blue Finned Tuna,
and can be greatly impacted by spills. The Deepwater Horizon spill, which
occurred off the Gulf of Mexico in 2010, posed an immediate threat to the
already endangered commercial fish population. The gulf serves as the
overfished tuna’s sole breeding ground leaving fishers and scientists knowing
that the spill signaled disaster for the year’s (and possibly longer) catch and
the population’s health. Regional phytoplankton also suffered greatly following
the spill; because of the oil’s sheen and viscous nature, the essential
requirements of phytoplankton growth were inhibited. The ocean-atmospheric gas
exchange equilibrium and blockage of solar radiation led to a significant
decrease in photosynthesis and phytoplankton growth. While the dissolved
portions of spilled oil create the majority of the biological concerns, the
gulf’s natural seeps support a microbial ecosystem in itself where specialized
bacteria are able to survive by oxidizing the hydrocarbons. These organisms
provide alternative methods to oil spill clean up, referred to as
bioremediation and biodegradation—the natural process in which bacteria are
fertilized with nutrients to facilitate the degradation, and thereby
remediation, of PAHs and other hydrocarbons present.
Clean Up: Biodegradation
The first response to an oil spill
is how to go about removing the oil as quickly, cheaply, and ecologically safe
as possible. Several methods are available for oil removal and each involves
specialized equipment and educated teams of workers to achieve. The mechanical
methods to cleaning up a spill involve booming it, where long floating
connected barriers physically stop the further spread of oil, and then removal.
Once the oil is contained workers are able to removal the oil carefully with
the use of vacuums, sorbents (which act like a sponge soaking up the oil),
shoreline removal by heavy machinery and finally chemical and biodegrading
agents. Chemical agents are used to lift the oil off and require special
permission to ensure safety. Mechanical methods of removal are encouraged to be
used to the fullest degree first before considering alternate methods, leaving
chemical methods to be used only as a secondary role, if at all.
Oil is a naturally occurring product
and is by definition biodegradable. Degradation by microbes is an accepted
method of oil removal, Figure 4, but may often be limited by the
supply of inorganic nutrients. In this way, microbes can be fertilized with
inorganic nutrients, including nitrates, in order to facilitate quick removal
of oil. The microbes, which occur around natural oil seeps deep in the ocean,
are able to oxidize the hydrocarbons and effectively remove them from the
environment. Bioremediation by way of microbes proves to have its share of
downsides. Environmentalists and scientists urge that as much physical removal
of oil be done first, only using the microbes as a facilitator for the
remaining oil. In this sense the microbes can only do so much to assist.
Because the microbes rely only limiting nutrients, nitrogen and phosphorus, as
well the issue of over fertilization because a major concern. Even a little too
much fertilizer to the microbes and an unwarranted algae bloom can occur. This
bloom and productivity can lead to hypoxic zones where organisms struggle to
survive due to decreased dissolved oxygen levels. Due to the biological risks
of bioremediation, microbes have only been used along the coast, rocky shores
and salt marshes. As of 2010 no microbe application has ever been applied to
deep sea or open ocean spills. This, in turn, causes reduced information and
data on how to properly control the microbes and the possible side effects of
raising them. To some, the Exxon Valdez
spill showed a good response to the application of phosphorus and nitrogen
application and the environment suffered no harm; others believed that the
large application of fertilizer to a usually nutrient-poor region would have
ramifications in the form of algae growth.
In an effort to synthesize data
collected from peer-reviewed journals on the toxicology reports of the Exxon
Valdez spill and the affects to the biota of the region. Government protocol
articles outlining appropriate clean up methods for oil spills, the effects of
oil emulsions with regards to water chemistry and biota, were examined as well.
It was found that the water collected from the oil spill off of the Gulf of
Alaska contained “well below” the acceptable standard for polycyclic aromatic
hydrocarbons (PAHs). Marine ecosystems were shown to be negatively affected by
these chemicals as they were known to be endocrine disrupters and carcinogenic.
Appropriate methods of removal, notably physical and bio mediating methods,
were applied to quickly remove the oil. Oil spill assessment and removal at sea and
along the coast, as well as ecological effects demonstrated through Blue Finned
Tuna, phytoplankton and oil digesting microbes were taken into account. Blue
Finned Tuna and phytoplankton serve as proxies for the devastating impact that
PAHs and other hydrocarbons can have on the ecosystem. While oil spills, in
reality, are inevitable, the removal of them have become more understood
through models. Studies since the Exxon Valdez spill provide, and continue to
provide, data to support models for ecological reactions and effects to spills.
G. Wells, James N. Butler and J.S. Hughes, 1995, Exxon Valdez Oil Spill: Fates and Effects in Alaskan Waters, ASTM STP
1219, Eds. American Society for Testing and Materials, Philadelphia
Oceanic and Atmospheric Administration, n.d. Web. 12 Dec. 2015. “How Do
Oil Spills Get Cleaned up on Shore? Response.restoration.noaa.gov.” How
Do Oil Spills Get Cleaned up on Shore? Response.restoration.noaa.gov.
Abbriano, R.M., M.M. Carranza, S.L. Hogle, R.A.
Levin, A.N. Netburn, K.L. Seto, S.M. Snyder, SIO280, and P.J.S. Franks. 2011.
Deepwater Horizon oil spill: A review of the planktonic response. Oceanography
Charles H. Peterson,
Stanley D. Rice, Jeffrey W. Short, Daniel Esler, James L Bodkin, Brenda E.
Ballachey, David B. Irons, 19 Dec. 2003. Long-Term Ecosystem Response to the
Exxon Valdez Oil Spill. Science Mag. Vol
W. F. M., M. G. Milner, D. M. Jones, K. Lee, F. Daniel, R. J. P. Swannell, and
I. M. Head. “Robust Hydrocarbon Degradation and Dynamics of Bacterial
Communities during Nutrient-Enhanced Oil Spill Bioremediation.” Applied
and Environmental Microbiology 68.11 (2002): 5537-548. Web.
Erich R. Gundlach, Miles O. Hayes, 1978.
“Vulnerability of Coastal Environments to Oil Spill Impacts”. University of South Carolina, v. 12. 4 http://www.oil-spill-info.com/Publications/1978_MTS_Vulnerability_ESI.pdf