Introduction Tankers and cargo ships that carryoil to be refined and processed are under constant scrutiny by the public andthe government when it comes to environmental concerns. Regulations are put inplace to ensure the safety of the crew on board as well as the protection ofmarine environments and ecosystems. Although crude oil transportation, onpaper, should operate smoothly it has occurred to such a large extent thatstricter regulations and clean up protocol are needed to ensure the ecological safetyand future of fisheries, marine biodiversity and to protect against unnecessarypollution. Figure 1. Whileoil spills might not pose an immediate threat to humans on land, it should beof great concern to those who seek the protection of the resources availableand the environment and the long term affects associated with them. Oil is immiscible in seawater andforms an emulsion which causes broken up oil droplets to be suspended in thewater column. The oil-water emulsion poses a myriad of concerns for ocean waterchemistry. Understanding the economic, environmental and biochemical impacts ofsmall scale spills and large scale-media present spills, like those of theDeepwater Horizon spill or the Exxon Valdez spill, are of great necessity.
Thedetrimental effects to marine wildlife is popular knowledge to most of thepublic and images of water fowl coated in thick layers of crude oil circulateon television; yet the issues are still occurring and clean up efforts remainexpensive and time consuming and at a cost, ultimately, to the affectedecosystems and its inhabitants. Understanding that the issue of oil spilldisasters are much more than birds stuck in oil slicks or animals who areunable open their eyes or swallow because of the entrapped oil on theirmembranes, requires that scientists, and most importantly the government andpublic, become educated on the effects that oil has on marine fauna. Whileprevention and clean up become the concern for oil companies and thegovernment, understanding the side effects of oil spills on fisheries and theecosystem becomes the concern, and responsibility, of the scientist and theconsumer. In an endeavor to synthesize datacollected from peer-reviewed journals and government protocol articles, theeffects of oil emulsions, as a result from oil tanker spills, with regards towater chemistry and biota, will be examined. Oil spill assessment and removalat sea and along the coast, as well as long term ecological effects will betaken into account.
Chemical Evaluation ofOil-Water Emulsion Oil Spills are quite common, althoughnot always presented in the media, but only make up a lesser amount of marineoil pollution. It becomes the responsibility of the company, and associatingscientists, to assess the impact of the spill to determine any short and longterm affects to the water column and biota present. Before the Exxon Valdezspill information available for the construction of in lab risk-assessmentmodels were limited. These risk-assessment models are necessary to predict theecological impact of oil spills along the coast and offshore. With a staggering42 million gallons of crude oil spilled along 2000km of pristine shoreline inthe Gulf of Alaska, the Exxon Valdez spill is surprisingly not the greatest oilspill in recorded history Figure 2. Thespill called for a reform in model predictions clean up assessment and protocoland 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-qualityassessment tests were preformed on more than 5000 water samples to obtain amore complete understanding of oil’s interaction with seawater following thespill. The water samples collected were from offshore locations: areas throughwhich the oil had spilled, drifted and was adjacent to (regions of water thatwere 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 aromatichydrocarbons (PAHs) (Wells et al, 1995).Scientific literature and medical reports have shown that PAH’s are carcinogensand act as endocrine disrupters. This poses major threats and health concernsto fisheries and marine biology. This should be of great concern, and is, tothe scientific and public community as these chemicals are spilled in largequantities and can remain suspended, even if in considered low concentrations, forextended periods of time in the water column. The concentrations of total PAHs fromthe toxicological reports were used to determine the relative toxicity of thewater and the harm and any associated risks that were posed to marineorganisms. Scientists tested the water samples collected shortly after thespill (about a week’s time) to determine the concentration and distribution ofthe hydrocarbons present within the water column.
The examinations were followedup with toxicity evaluations, which were then compared to the known PAHsensitivity levels of locally established organisms. The test results of thechromatographic evaluations preformed by Exxon showed that the measured PAHlevels were “well below” Alaska’s water quality standard of 10ppb totalaromatic hydrocarbons; furthermore, they showed a standard of consistency whencompared against tests run by the National Oceanic and AtmosphericAdministration (NOAA) who collected water samples from the affected regionduring the same period of time (Wells et al, 1995). With regards to waterquality standards set in place by the Alaskan government and according toscientific literature already set in place, the measured concentration of PAHs inthe water samples collected showed that the oil spill posed little to no threatto the ecosystem and any organisms present, including both marine animals andplants. These findings, however, only take into account immediate organism mortalitydue to PAH toxicity and failed to preform any follow up examinations to gather findingson possibly lingering long term side affects on long lived organisms (those ofseveral years) or across generations. These tests would have showed ifhydrocarbons that lingered in the water caused delayed side effects orgenerational birth defects.
Effects on Biota and BioticResponse Oilspills have detrimental affects on marine populations due to PAHs’ physical andchemical characteristics. Polycyclic Aromatic Hydrocarbons are carcinogenic andendocrine disrupters leading to high mortality rates soon after the spill.Crude oil’s physical properties can leave water fowl and other organisms coatedin a thick layer of grease preventing sight, proper respiration and feeding. Themethods 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 throughcareful assessment and understanding that a model and plan of action be carriedout to remove the oil efficiently and effectively. Oil’s poisonous properties can leadto problems as a result of inhalation or ingestion, and external exposure,which can lead to membrane and eye irritation.
The oil, as it is popularlyshown on television commercials, can smother small fish, birds and otheraquatic wildlife. This reduces the organism’s ability to feed, breathe andregulate body temperature. A large number of immediate deaths following an oilspill are from organisms being coated in oil and dying from hypothermia due tolack of heat regulation.
Since most PAHs float on the surface water and all areimmiscible in water organisms, such as sea otters and water fowl, become theimmediate concern. Large numbers of sea birds have been recorded smothered anddead from the oil. Figure 3.
Asthe oil breaks up into the water column, and as it comes to shore, other marineorganisms, such as snails and clams, become targets. It is important to distinguishbetween the two types of oil that can be spilled. Different chemical andphysical properties lead to varying resonance times in the environmentdepending on if an oil is considered “light” or “heavy”.
Lighter oils, such asthose used for fuel like gasoline and diesel, are much more volatile thatheavier oils. These oils are able to evaporate fairly quickly because of theirvolatility and can leave the environment within several days. An increase insurface area due to a spill will decrease the resonance time further. Theselighter oils, however, pose severe immediate risks as they are quite flammableand are considered toxic. Even to humans, inhalation and external skin exposureto fuel oils can cause health problems and death to affected organisms. “Heavy” oils, such as bunker oilused to fuel cargo ships and vessels, are considerably more viscous, darker incolor and can remain sticky for extended periods of time.
If not removed heavyoils have a longer resonance time (months up to years) in the environment andcan persist without much degradation. Heavy oils pose significantly less toxicityissues, with respect to the carcinogenic lighter oils, to organisms and areinstead concern for hypothermia due to lack of temperature regulation. As thethick sticky oil coats the organism, the organism loose the functional abilityto regulate its body heat and can die quickly. Reports have also shown longterm exposure can lead to tumor growth in some species. Often overlooked, especially by thepublic, are the dynamics of the plankton population—including phytoplankton,zooplankton, marine bacteria and fish larvae—and their ecological responses tooil spills (Abbriano et al, 2011). Being subject to the currents, fish larvaeare of extreme importance to commercial fisheries, notably the Blue Finned Tuna,and can be greatly impacted by spills. The Deepwater Horizon spill, whichoccurred off the Gulf of Mexico in 2010, posed an immediate threat to thealready endangered commercial fish population.
The gulf serves as theoverfished tuna’s sole breeding ground leaving fishers and scientists knowingthat the spill signaled disaster for the year’s (and possibly longer) catch andthe population’s health. Regional phytoplankton also suffered greatly followingthe spill; because of the oil’s sheen and viscous nature, the essentialrequirements of phytoplankton growth were inhibited. The ocean-atmospheric gasexchange equilibrium and blockage of solar radiation led to a significantdecrease in photosynthesis and phytoplankton growth. While the dissolvedportions of spilled oil create the majority of the biological concerns, thegulf’s natural seeps support a microbial ecosystem in itself where specializedbacteria are able to survive by oxidizing the hydrocarbons. These organismsprovide alternative methods to oil spill clean up, referred to asbioremediation and biodegradation—the natural process in which bacteria arefertilized with nutrients to facilitate the degradation, and therebyremediation, of PAHs and other hydrocarbons present.
Clean Up: Biodegradationand Bioremediation The first response to an oil spillis how to go about removing the oil as quickly, cheaply, and ecologically safeas possible. Several methods are available for oil removal and each involvesspecialized equipment and educated teams of workers to achieve. The mechanicalmethods to cleaning up a spill involve booming it, where long floatingconnected barriers physically stop the further spread of oil, and then removal.
Once the oil is contained workers are able to removal the oil carefully withthe use of vacuums, sorbents (which act like a sponge soaking up the oil),shoreline removal by heavy machinery and finally chemical and biodegradingagents. Chemical agents are used to lift the oil off and require specialpermission to ensure safety. Mechanical methods of removal are encouraged to beused to the fullest degree first before considering alternate methods, leavingchemical methods to be used only as a secondary role, if at all. Oil is a naturally occurring productand is by definition biodegradable.
Degradation by microbes is an acceptedmethod of oil removal, Figure 4, but may often be limited by thesupply of inorganic nutrients. In this way, microbes can be fertilized withinorganic nutrients, including nitrates, in order to facilitate quick removalof oil. The microbes, which occur around natural oil seeps deep in the ocean,are able to oxidize the hydrocarbons and effectively remove them from theenvironment. Bioremediation by way of microbes proves to have its share ofdownsides. Environmentalists and scientists urge that as much physical removalof oil be done first, only using the microbes as a facilitator for theremaining oil. In this sense the microbes can only do so much to assist.
Because the microbes rely only limiting nutrients, nitrogen and phosphorus, aswell the issue of over fertilization because a major concern. Even a little toomuch fertilizer to the microbes and an unwarranted algae bloom can occur. Thisbloom and productivity can lead to hypoxic zones where organisms struggle tosurvive due to decreased dissolved oxygen levels. Due to the biological risksof bioremediation, microbes have only been used along the coast, rocky shoresand salt marshes. As of 2010 no microbe application has ever been applied todeep sea or open ocean spills. This, in turn, causes reduced information anddata on how to properly control the microbes and the possible side effects ofraising them. To some, the Exxon Valdezspill showed a good response to the application of phosphorus and nitrogenapplication and the environment suffered no harm; others believed that thelarge application of fertilizer to a usually nutrient-poor region would haveramifications in the form of algae growth. Conclusion In an effort to synthesize datacollected from peer-reviewed journals on the toxicology reports of the ExxonValdez spill and the affects to the biota of the region.
Government protocolarticles outlining appropriate clean up methods for oil spills, the effects ofoil 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 ofAlaska contained “well below” the acceptable standard for polycyclic aromatichydrocarbons (PAHs). Marine ecosystems were shown to be negatively affected bythese 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 andalong the coast, as well as ecological effects demonstrated through Blue FinnedTuna, phytoplankton and oil digesting microbes were taken into account. BlueFinned Tuna and phytoplankton serve as proxies for the devastating impact thatPAHs and other hydrocarbons can have on the ecosystem. While oil spills, inreality, are inevitable, the removal of them have become more understoodthrough models. Studies since the Exxon Valdez spill provide, and continue toprovide, data to support models for ecological reactions and effects to spills.
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