OIL SPILL IN THE GULF OF MEXICO (2010): CAUSES, CONSEQUENCES - ENVIRONMENT - 2024

The oil spill in the Gulf of Mexico in 2010 is the largest environmental disaster to have occurred in the United States, as a consequence of the explosion, fire and shipwreck of the semi-submersible platform Deepwater Horizon in charge of the British Petroleum (BP) company.

The platform was extracting oil at a depth of 5,976 m, in the Macondo well, located north of the Gulf of Mexico 75 km off the coast of Louisiana, in the exclusive economic zone of the United States.

Oil spill in the Gulf of Mexico. Source: kris krüg, via Wikimedia Commons.

The spill lasted for more than 100 continuous days, from April 20, 2010, when the platform explosion occurred, until August 5 of that same year, when the well was finally sealed.

Investigations have revealed that this incident occurred due to decision making that prioritized speed and cost reduction during the oil extraction process.

It is estimated that almost 5 million barrels were dumped into the waters of the gulf, with dire effects on wetland ecosystems and marine biodiversity. However, the real effects of this spill have yet to be assessed.

Among the mitigation actions that were taken into account during the spill, and the following days, the direct collection and burning of crude oil, wetland washing and chemical dispersants stand out.

Causes

Investigations carried out after the wreck of the platform reveal a set of wrong actions based on speeding up processes and reducing costs, violating industry guidelines and ignoring safety tests.

At the time of the accident, the Macondo well exploitation program was 43 days late, which translates into an additional $ 21.5 million, nothing more for the rental of the rig. Probably, economic pressures forced a series of wrong decisions that triggered a great catastrophe.

According to a report on the causes of the incident, there were errors in the process and in the quality of the cementing at the bottom of the well, which allowed the hydrocarbons to enter the production pipeline. In addition, there were failures in the fire control system, which should have prevented the gas from igniting.

Consequences

The explosion and subsequent fire on the platform caused the death of 11 people belonging to the technical personnel operating on the Deepwater Horizon platform.

As a whole, the oil spill was estimated at 4.9 million barrels, discharged at a rate of 56 thousand barrels per day, which reached an area of ​​86,500 to 180,000 km ².

Deepwater Horizon fire. Source:

Geographic impact

According to the United States Federal Fish and Wildlife Service, the states most affected by the oil spill were Florida, Alabama, Louisiana, Texas and Mississippi.

The impact on Mexican coasts was also reported.

Consequences of the spill on biodiversity

Wetlands

The effect of the oil spill from the Macondo well on the vegetation of the wetlands includes both acute short-term damage and chronic damage that is evident over a longer period.

The main acute damage to marshes occurs when plants suffocate due to anoxic conditions created by multiple coatings of oil. With the death of the vegetation, its function in containing the substrate ceases, the soil collapses, floods and there is no replacement of plants.

Marshes affected by the oil spill. Source: NOAA's National Ocean Service, via Wikimedia Commons.

During the month of November 2010, the US Federal Fish and Wildlife Service identified 1,500 kilometers of coastline with the presence of crude oil. Ecosystems of marshes, mangroves and beaches were affected.

A 2012 study on the composition of the microbial community of wetlands impacted by the spill showed a decrease in the population size of anaerobic aromatic degraders, sulfate reducers, methanogens, nitrate to ammonia reducers, and denitrifiers.

In this sense, the results of the research indicate that the effects of the spill influenced the structure of the populations involved in the biogeochemical cycles of nutrients. These alterations show a possible deterioration in the environmental benefits of the wetlands affected by the spill.

Birds

The birds of the Gulf of Mexico were affected by the oil spill in the Macondo well mainly due to loss of buoyancy and the properties of their plumage as thermal insulation in cases in which their body was covered with oil, and due to ingestion of crude oil. through food.

Pelican covered in oil. Source: Louisiana GOHSEP, via Wikimedia Commons.

Investigations by the US Fish and Wildlife Service in mid-November 2010 counted 7,835 birds affected by the oil spill.

Of the total, 2,888 specimens were covered in oil, of which 66% were dead, 4,014 showed evidence of internal contamination due to ingestion of crude oil, of which 77% did not survive, and 933 individuals died, whose level of contamination was unknown..

These values ​​are an underestimation of the real numbers, as they do not include migratory bird data.

Mammals

Mammals affected by the spill include both those that inhabit the marine environment and those that are distributed in terrestrial habitats influenced by the spill, with marine mammals being the most vulnerable.

Marine mammals such as dolphins and sperm whales were affected due to direct contact with the oil that causes skin irritations and infections, poisoning from ingestion of contaminated prey and inhalation of petroleum-derived gases.

The US Federal Fish and Wildlife Service, as of early November 2010, had identified 9 live mammals, of which 2 were covered in oil. Of these only 2 were returned to freedom. 100 dead individuals were also captured, of which 4 were covered in oil.

Reptiles

Six species of sea turtles stand out among the affected reptiles. Of 535 turtles captured alive, 85% were covered in oil, of these 74% were cared for and released alive. Of 609 individuals collected dead, 3% were covered with crude oil, 52% had crude oil remains, and 45% had no obvious signs of external contamination.

Corals

Corals in the Gulf were also affected by the oil spill. Exposure to crude oil and chemical dispersants resulted in the death of coral colonies and in other cases caused damage and physiological stress marks.

Fishes

The fish affected in the spill are mainly the pale sturgeon (endangered species) and the Gulf sturgeon (threatened species). Damage can occur from ingesting crude directly or through contaminated plankton. Crude oil is also known to alter the cardiac development of these animals.

Plankton

Contact with oil can contaminate plankton, which form the basis of the food chain for marine and coastal wetland ecosystems.

Solutions / measures

Measures taken offshore

Capture

In a first phase, efforts were concentrated on capturing oil in open waters with the use of barriers, in order to prevent it from reaching the coasts, from where it is much more difficult to extract.

Through this method, 1.4 million barrels of liquid waste and 92 tons of solid waste were collected.

Barriers to collecting oil on the high seas. Source: US Fish and Wildlife Service Southeast Region, via Wikimedia Commons.

Burning

This method consists of setting fire to masses of crude oil accumulated on the surface. It is considered one of the most effective techniques in removing the most toxic compounds from oil, such as aromatic compounds.

During the days after the spill, 411 oil burns were carried out on the surface of the water, thereby controlling 5% of the oil spilled.

Chemical dispersants

Chemical dispersants are a mixture of surfactants, solvents and other chemicals, which, like soap, act by breaking the oil into small drops, which are then distributed in the water column and can be degraded by microorganisms.

It is estimated that 8% of the spilled oil was dispersed using this method.

BP applied amounts of chemical dispersants in excess of those allowed. In addition, they applied it both on the ocean surface and at the submarine level, even though the latter procedure was in a phase of experimental tests to evaluate its collateral effects.

Chemical dispersants have a harmful effect on marine life, so many authors think that in this case "the remedy may be worse than the disease."

On the one hand, it consumes oxygen in large quantities causing large anoxic areas, which cause the death of phytoplankton, affecting the base of the trophic chain. On the other hand, it is known that the molecules of the chemical dispersant are accumulated in the tissues of living organisms.

The long-term effects of the use of chemical dispersants to mitigate the effects of the Gulf of Mexico spill on marine life have yet to be evaluated.

Wetland mitigation and cleanup

During the days of the spill, actions were focused on gathering information on the presence of oil on the coast. While the spill continued, collecting oil and cleaning wetlands was considered a secondary task due to the risk of recontamination.

Therefore, for more than 100 days, only large volumes of oil were removed from beaches and marshes, but not thoroughly cleaned. Thus, wetland cleanup was taken as a priority once the well was sealed and the spill stopped.

The main methods used for cleaning marshes and mangroves were mechanical harvesting and washing, given the environmental sensitivity of these ecosystems.

Beach cleaning. Source: National Institute for Occupational Safety and Health, via Wikimedia Commons

Mechanical harvesting

This technique included the manual collection of crude remains. It can be done with the help of shovels, rakes, vacuum cleaners and other equipment. It was used mainly on sandy beaches, from where 1,507 tons of oil were removed.

Washed

This technique was used to remove the remains of oil from the swamps. It consists of doing a low pressure wash to push the oil to areas where it can be aspirated.

References

1. Corn, ML and Copeland, C. (2010). The Deepwater Horizon oil spill: coastal wetland and wildlife impacts and response. Congressional Research Service. 29pp.
2. Crone, TJ and Tolstoy, M. (2010). Magnitude of the 2010 Gulf of Mexico Oil Leak. Science 330 (6004): 634.
3. Deleo, DM et al. (2018). Gene expression profiling reveals deep ‐ sea coral response to the Deepwater Horizon oil spill. Molecular Ecology, 27 (20): 4066-4077.
4. Hee-SungBaea et al. (2018). Response of microbial populations regulating nutrient biogeochemical cycles to oiling of coastal saltmarshes from the Deepwater Horizon oil spill. Environmental Pollution, 241: 136-147.
5. Velazco, G. (2010). Possible causes of the Deepwater Horizon rig accident. Petrotecnia 2010: 36-46.
6. Villamar, Z. (2011). What was the official US view of the environmental damage caused by the oil spill from the Macondo well? North America, 6 (1): 205-218.