Polycyclic aromatic hydrocarbons (PAHs) are potential atmospheric pollutants comprising of used aromatic rings and do not have substituent or heteroatoms. They are found in coal, oil and deposits of tar and are byproducts of both biomass and fossil fuel burning. They are of great concern when they are pollutants. This is because they easily mix with oil as opposed to water, which explains their natural occurrence in the oil.
Deposits of natural crude oils contain significant quantities of PAH’s that crop up when natural molecules are converted chemically to aromatic hydrocarbons (Review of environmental consequences of BP Deepwater horizon… 3). PAHs are therefore harmful to human health and plants. Different compounds of PAH’s have different effects to these organisms.
As a result, when BP oil spill occurred there was an increased concern that PAH’s might destroy seafood and plants in the Gulf of Mexico. Previous oil spills such as Exxon Valdez in the coast of Alaska left marks of environment impact like oil puddles, which still exists in the Prince William Sound. In addition, oil spills can also be traced in Panama water of Bahia Las Minas some 25 years later.
The quantities of the oil spilled by these accidents into the ocean are insignificant compared to the number of gallons that BP spill in the Gulf of Mexico, jetting into the ocean every day from April 20 2010 and lasting for over three months.
This therefore means that its impacts will be enormous and it is unknown how long it will last. This paper explores the likely impacts projected to be caused by the oil spills because of its PAH’s compounds, as well as what has been observed so far.
Background
Within a week, Transoceanic oil spill had been reported to cause a spill of 250 000 barrel of oil into the ocean, making the president of United States to declare it a national disaster. Technical fault in the Macondo have been blamed for the eruption of fire in the rig that caused the spill into Deepwater Horizon of Transocean. Since the fire continued for almost three months, significant oil spills continued to flow into the ocean (BP 14).
Unknown quantity of crude oil was released into the Gulf of Mexico from a 5,000 ft depth in Mississippi gorge. As a result, different ecosystems in the Gulf basin were subjected to unknown negative effects due to the quantity of oil released.
However, the effects on natural resources depend on a number of factors including quantity of oil, composition and organism contact. These impacts may be in the offshore, on mid-level mixing layer, as well as at the sea floor. On the other hand, onshore impacts may take place on shorelines, coastal habitats and near shore.
To reduce the impact of oil on different ecosystems, dispersants are used to change its chemical and physical composition, and thus transform its transportability, potential effects and fate. The choice to use dispersant is arrived at because oil is generally dispersed through wind and waves actions. As a result, dispersants help to increase the quantity of oil that physically combines with the water column.
This reduces the slick potential contamination of shoreline habitats and fauna or effects on living things that exist in the surface water such as turtles, marine mammals and birds. By encouraging oil dispersion into the water column this way, dispersant makes benthic biota and water column vulnerable to oil spills.
Consequently, a decision that involves the use of dispersant to reduce the harmful effect of oil spills is a deliberate effort to increase the hydrocarbon weight on one ecosystem component such as the water column, while reducing the weight on others such as coastal wetlands.
This exchange indicates the complex nature of many factors that are considered , which also include oil type, spills volume, the weather and sea state, degree of turbulence, the depth of water, as well as the stages of life that organism living there are in.
Impact of oil spill is inevitable regardless of the decision taken to curb its spread. The main decision is to decide which ecosystem needs to be sacrificed in order to protect the other (Review of environmental consequences of BP Deepwater horizon…1). Oil spills affect marine ecosystems in different ways.
Effects of oil on marine ecosystem
The most toxic compounds of petroleum are the aromatic hydrocarbons. This can be demonstrated by the direct correlation between acute toxicity of refined and crude petroleum in marine organism with light aromatic hydrocarbons such as benzene to phenenthrene concentration. The petroleum chronic effects are linked to 4 and 5-ring aromatic hydrocarbons where some are known carcinogens.
However, due to their low solubility, these hydrocarbons hardly survive in acute contaminated concentrations. On the other hand, aromatic hydrocarbons with single ring such as toluene, benzene, ethylbenzene and xylenes are explosive and generally lost quickly from water via evaporation.
Toxicity of crude and refined petroleum is therefore a factor of the slightly soluble and relatively constant phenanthrenes and naphthalenes. In addition, existence of rich heterocyclic compounds in many crude oils adds to their toxicity (Review of environmental consequences of BP Deepwater horizon… 3).
It was also revealed that crude oils, oil water dispersion and water soluble fractions were less toxic to the Gulf of Mexico invertebrates and fish, than expected toxicity of refined oils. It further shown that Benzene, toluene, ethylbenzene and xylene caused toxicity in WAF exposure and naphthalenes was the principal cause of toxicity in dispersed oil exposure.
Species death was also observed to rapidly take place within the first 24 hours of exposure. In addition, other long-term effects observed in white shrimp indicate that the animals are not necessarily healthy because they have survived the acute poisoning (Review of environmental consequences of BP Deepwater horizon… 4).
Particular impacts on species and ecosystems
Effects on the coastal wetlands in Gulf of Mexico
More than half of the coastal wetlands in 48 states are in the Gulf of Mexico coastal areas, with Louisiana making up about 40 percent of this. These wetlands are important for sprouting of fish species as well as human life protection. However, for over 50 years or so, the Gulf of Mexico has lost coastal lands at an alarming rate.
The impact of Deepwater Horizon oil spill on the coastal areas depends on the amount of oil that will get to these habitats as well as the length of time it will remain there. If large portions of oil cover vegetation on the coast shorelines, it may cause vegetation stress and its eventual death. As a result, roots may also die out and marsh soils weaken. This would accelerate the erosion of coastal shorelines by storms and waves (NOOA 1).
Effects to species
About ninety seven percent of Gulf of Mexico fish and shellfish are species dependent on estuaries as well as wetlands at a certain stage of the lifecycle. Louisiana coastal contribute a third of the total United States weight of fish harvested. Important habitat covers almost every part of the ecosystem in the area. They include floating surgassum mats, hard coral reefs, ledges, sandy beaches used by turtles for nesting, and many others.
In the beginning, fish that survive on the shallow water will be affected and eventually, when oil starts to sink even the ones that thrive in the bottom will not be spared. Generally, about 40 percent of the Gulf fish survive in the bottom and the impact on the fish community would be minimal if the oil spill remains on the surface. Consequently, if the oil reaches onshore or bottom of the shore, a large percent of the fish would be affected.
In addition, since most of the reef fish produce in spring and their eggs are carried by the current as opposed to their own control, oil spill might affect this process: That is, if current draw oil and eggs together, the larvae might not be able to escape from the oil.
Additionally, since some species depend on sargassum mats for habitats, they might be affected by the oil if it is trapped by the sargassum. In the state water, if oil reaches near-shore, it would affect all coastal species. In addition, it would also affect the migration pattern of fish, which spend their early life inshore water before moving to the ocean (NOOA 2).
Specific pelagic fish species are vulnerable to oil spills. A report published in 2005 documented the vulnerability potential to oil spills of some pelagic fish both larvae and adult. It shows that there are some known and predicted cyclic distribution of larvae and adults of yellow tuna, bluefin tuna, blackfin tuna, white marlin, blue marlin, wahoo, blue runner, dolphin, Atlantic flyingfish, spotin flyingfish, and ocean sunfish.
It also includes other species of surgassum community including planehead, sargassumfish and tripletail. Most of them lay many eggs with little yolk reserves and resulting larvae are small and depend on surface plankton. Among these species, bluefin tuna are the most economically viable and their only spawning ground in the western Atlantic is Gulf of Mexico (Review of environmental consequences of BP Deepwater horizon…3).
Their spawning period is between April and June and their larvae are highly concentrated in areas where Eddie currents meet the shelf. This makes them vulnerable to meet the oil currents. Other species of larvae are also anticipated to be vulnerable to come into contact with the oil slick at different periods of the year.
Summary of Environmental Impacts Observed so Far
Although scientific data has not been documented on the exact impacts BP oil spill and the dispersants used have had or will in the near future, articles have been published pointing some of the effects that have already been observed. One of these articles points to oil spills effects on the marine life in the Gulf of Mexico. It also projects that these effects will continue in the near future regardless of the period the flow takes.
Greatest damages to marine life continue to take effect at the bottom of the water as various species die due to the toxic effect of the rapidly spreading oil (Biello Para 1). According to “Review of environmental consequences of BP Deepwater horizon… 6” oil is not the most toxic substance that can harm turtle’s habitat.
Nevertheless, a huge oil spill in 1979 threatened the habitats of a specific endangered turtle. The population of Kemp Ridley was affected by the spill that threatened its nesting beaches in Gulf of Mexico after a blowout of drilling platform.
Prior to the 2010 oil spill, Gulf region harbored various species such as phytoplankton and sperm whales. A documentary compiled in this period indicated that this ecosystem still provided habitat to 15, 700 species, even though drilling continued to take place in the region (Biello Para 2).
Further, the area directly affected by the spill harbored 8,332 plants and animals species. This include 1200 fish species like Atlantic blue fin tuna, 1, 500 crustaceans such as crab, and 29 aquatic mammals such as bottlenose dolphins.
The oil spill is already having its impact on the marine ecosystem as its threatening the growth of small animals and plants that are necessary for the food web to be complete. These phytoplankton and zooplankton provides necessary food to various aquatic species such as fish and their removal would result in deaths or migration of these species further affecting the food web.
Effect on shrimp, oyster, crab and fish may take generations to be reversed especially because of the long time it would take for ecological succession of certain species. Some of these effects will not be easily observed as turtles and sperm whale may die and sink to the bottom of the ocean and thus remain invisible at the surface.
Further impacts will also be observed in case storms and floods such as hurricane blow the oil deep to wetlands in the Gulf oil. Scientist interviewed in this article observes that there is no data existing by now that shows exactly the impact BP oil spills have had.
Although he notes that what has been observed is death of birds, they have also recorded deaths of turtles and mammals although the causes of their deaths are not known (Biello Para 6). The greatest cause of alarm is not just the short term effect that oil spill has had but the long-term effect that can reverse marine ecosystem.
For instance, when it comes to crabs, oysters and shrimps to be hatched in this period will not and this will affect the species population years to come. This effect is also cumulative as removal of a whole generation and also reduction of energy in the surviving one by toxicity is also going to affect another generation that the removed one would have conceived.
Both phytoplankton and zooplankton are in contact with the oil because the surface is the one that is directly affected and that’s where they both live. Removal of zooplankton also affects shrimps larva because they depend on them for food. In addition to these effects on generation of species, oil species will also affect an endangered species in the North Atlantic Ocean known as Bluefin tuna.
This specie is a commercially attractive one and already about 80 percent of it has been harvested by Japanese and other fishing fleet. This fish only spawns in two areas in this oceanic region and Deepwater Horizon is one of them. Consequently, spawning will not take place in the region and this will affect the population of the species.
Conclusion
Oil contains polycyclic aromatic hydrocarbons, which are the worst pollutant in refined and crude petroleum. These are compounds with different numbers of cells membranes. These PAH’s have different toxicity concentration and their effect on marine life differs depending on their ability to dissolve in water and withstand evaporation.
Different literatures have documented the effects oil toxicity is projected to have on different types of marine ecosystems and species. They all seem to agree that the length of these impacts will last to unknown period of time.
On the other hand, scientists have been following the environmental impact of this toxicity on the ecosystem. From the ensuing literature, this paper has deduced that oil spill will have both short term and long term effects on the coastal wetland and marine life.
An important impact that needs to be mitigated includes the effect on population of certain species due to death of certain generation and weakening of the surviving as they lose energy in this period. In addition, oil spill will have a significant impact on the Gulf of Mexico aquatic ecosystem and this may necessitate long term mitigation measures to restore the disturbed ecological system.
For instance, its food web will be greatly affected and it will take many years for some species that will die because of deprivation of food. Generally, this is an example of how human interference can cause irreversible negative effects on an ecosystem.
Works Cited
Biello, David. The BP Spill’s Growing Toll on the Sea Life of the Gulf. Yale University website. 2010. Web.
BP, Deepwater Horizon Accident Investigation Report, 2010. Web.
NOAA. Shorelines and Coastal Habitats in the Gulf of Mexico. Us Department of Commerce. pp 1-2. 2010.