Environmental Impact of the Deepwater Horizon Oil Spill

The Environmental Impact of the Deepwater Horizon Oil Spill

The consequences of the 2010 Deepwater Horizon oil spill in the Gulf of Mexico extended beyond the 11 fatalities and 17 injuries suffered that day. The 4 million barrels of crude oil that spilled into the ocean over the ensuing 3 months also carried a significant environmental impact, some of which is still being felt today.

Below is a brief look at those environmental impacts that resulted from the explosion aboard the oil rig Deepwater Horizon on April 20, 2010, which left an oil slick on the surface of the ocean 100 miles wide.

3 Major Areas of Impact After Deepwater Horizon Spill

Effect on marine life

PAH, or polycyclic aromatic hydrocarbons, is a chemical that is carcinogenic in high concentrations and can interfere with biological processes. PAH was found up to 8 miles from the wreckage site and was later found to be causing cardiac arrest in fish. Additionally, pockets of methane led to oxygen-starved zones, which caused marine life to smother. Large numbers of fish kills in the area were reported.

Prior to the spill, only about 0.1% of fish in the Gulf of Mexico had lesions or sores. In the aftermath of the spill, that number spiked to 20%.

Pregnant dolphins in the Gulf of Mexico were found to have a higher incidence of in-utero infections, fetal issues, and late-term pregnancy failures. In fact, in the 6 years following the spill, over 170 stillborn and stranded juvenile dolphins have been found in Gulf waters, according to the National Oceanic and Atmospheric Administration.

Effect on birds

Effects were not limited to species who made their home in the water. According to the Audubon Society, over 1 million birds died as a result of the disaster. Oil inhibits birds' ability to maintain body warmth, and many were found on shore still alive and seeking shelter.

Groundwater impact

Experts theorize that the use of dispersants after the spill caused the oil to sink even more deeply into beaches. They also suspect that it may have affected the groundwater supply in that area.


It took nearly 3 months for the oil leak to be fully capped before the cleanup effort could commence. Some 48,000 people were hired to assist with the cleanup, and all were required to complete HAZWOPER training classes in advance.

Those working on marine vessels underwent a 40-hour HAZWOPER training course and many also took an 8-hour supervisor course as well. Training consisted of both site-specific and classroom modules.


The environmental impact of the Deepwater Horizon oil spill is still evident a decade later.

There is some hope though. The fishing industry in the area has seen their catches return to normal levels. Oysters in many areas of the gulf are returning. Tests on edible seafood caught in that area do not show excess hydrocarbons in the food supply in the region.

However, other species and areas are not showing the same kind of promise. Dolphin numbers are down. As late as 2013, Cat Island, an important bird rookery, was still devoid of the mangroves that had provided shelter, leading pelicans and other birds unable to use the area.

According to research undertaken by Mandy Joye, an oceanographer with the University of Georgia, the oil from the spill has settled to the seafloor, concentrating in thin sheets in some areas and deep pools in others. Joye claims that the submerged oil continues to shift around, and that it is impossible to determine at this point what the long term impact will be.

In 2015, federal officials claimed that it was still too soon to make any judgments about the long-term effects of the spill and the success of the recovery process.

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