The Lasting Legacy of the Deepwater Horizon Oil Spill

By Delaney Reynolds, SRC intern

This map of how far the oil reached on the surface level of the Gulf of Mexico exhibits that the coasts of Texas, Louisiana, Mississippi, Alabama, and Florida were impacted.
(Source: Huettel, M., Overholt, W. A., Kostka, J. E., Hagan, C., Kaba, J., Wells, B., & Dudley, S. (2017, December 22). Degradation of Deepwater Horizon oil buried in a Florida beach influenced by tidal pumping. Retrieved March 13, 2018, from pii/S0025326X1730903)

Mankind’s use of fossil fuels as an energy source can place our natural environment at grave risk, and nowhere is that more acute than in the Gulf of Mexico. The environmental threats the Gulf region faces from petroleum production and exploration are not just those that appear in the media immediately following an oil spill or similar catastrophe, but are events that leave a lasting, often unseen legacy that stands to pollute and destroy our natural environment and the creatures that live in it for generations.

The Deepwater Horizon, British Petroleum (BP), oil spill of 2010 was the largest marine oil spill in history and polluted the Gulf for 87 days by pouring an estimated 60,000 barrels per day at its peak, and over 3.19 million barrels in total, of petroleum into the Gulf’s environment (Pallardy). The oil’s effluence rapidly spread to over 1,000 miles on the coastlines of Texas, Louisiana, Mississippi, Alabama, and Florida and while the efforts to clean up beaches and the spill itself have had some success, remnants of oil remain buried in sediments and continue to dramatically disrupt life beneath the surface (Frost).

Florida State University researchers discovered that within a week of burial, two thirds of the oil that washed ashore was retained in coastal sediments and caused a decrease in biodiversity by over 50% (Huettel). Bacterial abundance increased drastically in heavily oiled sands as the bacteria thrived off the oil and, thus, caused bacteria blooms, lowering overall oxygen content. This decrease in oxygen content, in turn, caused the decrease of biodiversity as aerobic organisms either perished or migrated to areas with a higher oxygen content. However, within three months, a resurgence in microorganisms normalized biodiversity as they restocked the coastal waters with the oxygen that aerobic organisms’ survival necessitates. Not only does this exemplify the ability of aquatic ecosystems to replenish themselves after being exposed to stressors, but it also supplies us with knowledge of the types of microorganisms that could be utilized to clean up future spills, as well as any environmental impacts they may cause to other organisms.

One example of a lasting major environmental impact of the spill to other species from exposure to crude oil is pelagic fish cardiac and swim performance impairment which, in turn, has been found to lead to the inability of embryonic development. Mahi-mahi embryos obtained from the University of Miami Experimental Hatchery and yellow fin tuna embryos obtained from the Inter-American Tropical Tuna Commission’s Achotines Laboratory were collected as experimental specimen and exposed to different dilutions of crude oil collected from the Deepwater Horizon Oil Spill site, as well as varying levels of ultraviolet radiation (UV) exposure, for 96 hours in a pelagic embryo-larval exposure chamber (PELEC). Mahi-mahi specimens exposed to higher levels of UV radiation were found to have a nine-fold increase in toxicity from Deepwater Horizon crude oil increasing stress levels within the fish. Yellow fin tuna survival rates were found to be significantly higher in the PELEC system than in the agitated system, meaning their survival rate decreased by a measure of 20% when exposed to crude oil and UV radiation (Steiglitz). Events such as the Deepwater Horizon oil spill can challenge pelagic fish, especially embryos and their ability to develop correctly and survive. Thus, this research provides ways in which we can begin to predict the extreme environmental conditions species would face in future oil spills, as well as examine how remnants of oil preserved in sediments may affect spawning grounds among certain species.

Kemp’s Ridley sea turtle (Lepidochelys kempii) covered in crude oil
(Source: 20150504-noaa-announces-new-deepwater-horizon-oil-spill-searchable-database-web-tool.html).

Another example of the diverse and devastating impact that an oil spill can have can be found in northwest Florida, where the loggerhead turtle (Caretta caretta) has been found to have varying offspring densities in nests since the Deepwater Horizon spill in 2010. Using a before-after, control-impact statistical model, researchers from the US Fish and Wildlife Service and Florida Fish and Wildlife Conservation Commission examined the historical records of loggerhead turtle nest densities and compared them to nest densities after 2010. They found that loggerhead nest densities in 2010 were reduced by 43.7% following the Deepwater Horizon oil spill and approximately 251 nests were decimated by crude oil and cleanup efforts, having a long-term impact on population sizes (Lauritsen). The drastic decline is due in part to the oil that entered “nearshore areas and washed onto beaches along the northern Gulf of Mexico shoreline during the summer of 2010, requiring extensive, disruptive activities to remove contaminated beach sand, oil, and debris” (Lauritsen). Nesting densities increased to normal rates in 2011 and 2012 suggesting some loggerhead sea turtles avoided mortality from oil saturation. Researchers later estimated that at least 65,000 sea turtles perished in 2010, likely exacerbated by oil contamination (Pallardy).

There are few places on earth as lovely and naturally beautiful as the Gulf of Mexico. From its sandy white beaches, coastal marshes and abundant estuaries, to its serene salt waters, the Gulf region is a critical environment that humans and countless animal species rely upon for food, shelter, and recreation. Sadly, since 2010 when the Deepwater Horizon spill event took place, there have been at least 234 additional oil spills here in the United States as of December 2017 (ITOPF). And while the immediate impact of a spill is unacceptable, the lasting legacy such as sediments that retain oil particles long after a spill occurs and its impact on range of species across the food chain from microorganisms to sea turtles to mahi-mahi and yellow fin tuna should concern all of us. As populations continue to grow, so too will energy needs and this, along with the constant threat from yet another oil spill and the long-term implications its pollution has on our environment, makes managing these risks, while also embracing and evolving to sustainable energy solutions, critical to nature and humans alike.

Works Cited

Frost, E. (2018, February 28). Gulf Oil Spill. Retrieved March 15, 2018, from

Huettel, M., Overholt, W. A., Kostka, J. E., Hagan, C., Kaba, J., Wells, B., & Dudley, S. (2017, December 22). Degradation of Deepwater Horizon oil buried in a Florida beach influenced by tidal pumping. Retrieved March 13, 2018, from

ITOPF. (2017, December). Oil Tanker Spill Statistics 2017. Retrieved March 15, 2018, from

Lauritsen, A. M., Dixon, P. M., Cacela, D., Brost, B., Hardy, R., MacPherson, S. L., . . . Witherington, B. (2017, January 31). Impact of the Deepwater Horizon Oil Spill on Loggerhead Turtle Caretta caretta Nest Densities in Northwest Florida. Retrieved March 13, 2018, from

Pallardy, R. (2017, December 15). Deepwater Horizon oil spill of 2010. Retrieved March 15, 2018, from

Stieglitz, J. D., Mager, E. M., Hoenig, R. H., Alloy, M., Esbaugh, A. J., Bodinier, C., . . . Grosell, M. (2016, July 22). A novel system for embryo-larval toxicity testing of pelagic fish: Applications for impact assessment of Deepwater Horizon crude oil. Retrieved March 13, 2018, from Stieglitz et al.pdf&p=DevEx,5063.1

The Mess Left by the Gulf Oil Spill

By Jessica Wingar, RJD Intern

Oil spills are notoriously awful environmental events. The worst one to ever occur was on April 2, 2010 in the Gulf of Mexico. One of the Deepwater Horizon oil rigs exploded, killing eleven people, and causing copious gallons of oil to pour into the ocean. After eighty seven days, the rig was capped off, but the damage was already done. The environmental consequences of this spill are very wide ranging. The estimated amount of oil that spilled into the ocean is about 4.9 million barrels and that is probably a low estimate. With this amount of oil and because of ocean currents, this oil spread all around the Gulf of Mexico and into the entire water column. Of course, the animals living in this oil were and still are greatly affected by this spill, and future generations will continue to be effected. From stranded dolphins to oil covered turtles, the list goes on (Gulf Oil Spill).


An immediate effect of the oil spill: A scientist saving an oil covered turtle.

In addition, to the visible effects, there are many effects of the oil spill that occurred under the surface. Oil contains petroleum hydrocarbons, which are pollutants meaning that they are harmful to organisms that ingest them. These hydrocarbons can lead to the suppression of the immune system, which increases the likelihood of disease in populations. Therefore, increasing the likelihood of death in these organisms, and thus decreasing the populations of many organisms. The effects of these hydrocarbons also lead to a decrease in ability to respond to large changes in environmental factors (Whitehead, A, 2014).  However, there are more than just the effects on the present populations of marine organisms. There are many consequences of the spill that will be felt for generations to come.

The effects of oil on the development of fish are of high concern. It is of high concern because the oil from the rig has gone throughout the water column and to the surface. Many fish embryos develop in the surface water. Before the spill, the effect of a lot of crude oil was not an issue, but after this huge spill the worry of developmental problems has increased (Incardona, J.P., 2014).

Many studies have been done since the spill that observe the changes in fish development. One study conducted shortly after the spill looked at developing killifish embryos and adult organisms in order to see how they reacted to the oil. These fish were taken from marshy areas that had been directly affected by the fallout of the deepwater horizon spill. PCB is one of the main toxins in crude oil and these embryos exhibited activation of PCB responsive genes. Therefore, leading to decreased hatching, development, and survival of killifish. These effects are major concerns because killifish are the most abundant vertebrates in the Gulf of Mexico marshy environments (Whitehead, A. et al, 2012). In a study done using oil taken from the slick, amberjack, Bluefin tuna, and yellowfin tuna were raised in a lab and their heart development was observed. As the concentration of oil increased, heart rate decreased and arrhythmia was also observed. In addition to the problems in heart development, there were also physical developmental problems. Fins appeared to be reduced in size and there was decreased development of finfolds (Incardona, J.P., 2014). Another study observing mahi-mahi also showed an increase in heart rate as percentage of oil increased. These important pelagic species also had swimming challenges as they grew.

Picture2 (1)

Affects on the caudal finfolds

This same study looked at how the swim speed of mahi-mahi was affected by the Deepwater Horizon oil spill. The mahi were exposed to oil as embryos for 24 and 48 hour periods. Both time exposures showed that when these fish grew to juveniles they experienced a decrease in swim speed that they could maintain for long periods of time. Since it took about 25 days for these decreases to be seen, this study also found that there must be some delay in development as well caused by the polycyclic aromatic hydrocarbons, toxins, in the crude oil from the Deepwater Horizon Spill (Mager, E, 2014). Research is still continuing in order to find out more of the long term effects of this devastating oil spill. This research is increasingly important seeing as in years to come, these effects could be more pronounced in the ocean. In addition, if this research is done, then further work can be done to conserve the organisms that currently live in the Gulf of Mexico.


Gulf Oil Spill. (n.d.). Retrieved October 27, 2014, from

Incardona, J.P., Gardner, L.D., Linbo, T.L., Brown, T.L., Esbaugh, A.J., Mager, E.M., Stieglitz, J.D., French, B.L., Labenia, J.S., Laetz, C.A., Tagal, M, Sloan, C.A., Elizur, A, Benetti, D.D., Grosell, M, Block, B.A., and Nathaniel L. Scholz.  (2014). Deepwater Horizon crude oil impacts the developing hearts of large predatory pelagic fish. Proceedings of the National Academy of Sciences, 111(15): 7053-7061.

Mager, E.M., Esbaugh, A.J., Stieglitz, J.D., Hoenig, R, Bodinier, C, Incardona, J.P., Scholz, N.L., Benetti, D.D., and Martin Grosell. (2014). Acute Embryonic or Juvenile Exposure to Deepwater Horizon Crude Oil Impairs the Swimming Performance of Mahi-Mahi (Coryphaena hippurus). Environmental Science and Technology, 48(12): 7053-7061.

Whitehead, A. (2013). Interactions between Oil-Spill Pollutants and Natural Stressors Can Compound Ecotoxicological Effects. Integrative and Comparative Biology, 53 (4): 635-647.

Whitehead, A, Dubansky, B, Bodinier, C, Garcia, T.I., Miles, S, Pilley, C, Raghunathan, V, Roach, J.L., Walker, N, Walter, R.B., Rice, C.D., and Fernando Galvez. (2012). Genomic and physiological footprint of the Deepwater Horizon oil spill on resident marsh fishes. Proceedings of the National Academy of Sciences, 109 (50): 20298-20302.


Conservation research: Recovery of salt marshes after the BP oil spill

by Evan Byrnes, RJD intern

Oil spill damage has been a hot area of interest, especially since the BP Deepwater Horizon Spill in 2010. This is because oil spills can affect flora and fauna for generations, especially in coastal wetlands where decomposition is slow due to the low energy and anoxic environment. Coastal wetlands are very important habitats. They are commonly used for reproduction by various organisms, provide protection from shoreline erosion, regulate gasses and nutrients, support fishery and ecotourism industries, and much more.

Figure 1 from McCall and Pennings 2012, showing “typical conditions at oiled sites”

Coastal wetlands are a predominant habitat in the Gulf of Mexico, yet over 3000 production platforms are active in the Gulf. This brings about major concern for potential damage to these crucial habitats. Therefore many laboratory studies have been completed studying the damage done by oil spills. However, laboratory studies have not proved pertinent because they cannot duplicate the effect of natural wave and tidal action and normally have short durations. For these reasons, McCall and Pennings took it upon themselves to conduct a field study following the BP Deepwater Horizon Spill studying the effect with natural conditions and over a longer period of time.

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