The Ecological Impact of Oil Spills

By Jkala M. Assar

The Exxon Valdez spill of 1989 slicked over 11,000 square miles of water and altered 1,300 miles of pristine Alaskan coastline. Originally, wildlife mortality was estimated to be nearly 250,000 sea mammals, fowl, and other coastal marine organisms, but this figure was discredited in a 2003 study by the Exxon Valdez Oil Spill Trustee Council published in the December 19, 2003 issue of Science magazine. The original findings were questioned again in 2008 as part of an ongoing study of the Prince William Sound by the National Oceanic and Atmospheric Administration.

Dr. Charles Peterson, alumni distinguished professor of marine sciences at the University of North Carolina at Chapel Hill and lead investigator for the Exxon council, stated in the aforementioned 2003 report, “Studies we reviewed and synthesized showed that oil has persisted in surprisingly large quantities for years after the Exxon Valdez spill in subsurface reservoirs under course intertidal sediments. This oil was sequestered in conditions where weathering by wave action, light and bacteria was inhibited, and toxicity remained for a decade or more.”

In contrast, the British Petroleum oil spill differs in both quantity and environmental disruption due to its location and magnitude. In some areas, the spill spans the entirety of the water column, a conceptual cross section of water from the ocean floor to its surface. Researchers have detected areas of dispersed underwater oil 30 miles long, seven miles wide, and hundreds of feet thick, according to Dr. Samantha Joye, a University of Georgia professor of marine science and member of the NOAA expedition that discovered the plumes. On her UGA Gulf oil spill page,, she further asserts that its location separates it from other accidents of its type, and the spill will most likely extend the duration of what is known as a seasonal hypoxic zone, a time period in the marine ecosystem that occurs when dying algal blooms prompt bacteria to feed on them.

The Gulf is already a victim to this phenomenon, which is caused by industrial pollutant runoff from the Mississippi River. The algal blooms in the Gulf of Mexico help to clear water of excess fertilizer and factory by-products from the Midwest, but the introduction of crude oil and dispersants will exacerbate the hypoxia during this time period.

According to Scientific American in a June 3, 2010 article by David Biello titled “How will the Oil Spill Impact the Gulf’s Dead Zone?”, oil and oil dispersants extend the seasonal dead zone by further depleting oxygen stores and disrupting the marine food chain, either eliminating wildlife or sending it elsewhere for food.

Oil dispersants, which work by breaking up certain types of oil and redistributing them into the water column where they are bio-degraded by microorganisms, are themselves toxic and cause alterations in the Gulf’s ecosystem. As referenced from the Material Safety Data Sheet for Corexit, a commonly used dispersant, the solvent 2-Butoxyethanol is present, amongst other poisons. 2-Butoxyethanol is long lived in the environment, affects the reproductive systems of humans, and is carcinogenic.

Effect on Gulf Organisms

In a May 1, 2010 Washington Post article by David A. Fahrenthold and Juliet Eilperin titled “Oil plumes under Gulf of Mexico after spill are a toxic double-hazard”, Dr. Joye again expounds on the spill’s effect on wildlife by saying, “So, first you have oily water that may be toxic to certain organisms and also the oxygen issue, so there are two problems here. This can interrupt the food chain at the lowest level, and will trickle up and certainly impact organisms higher. Whales, dolphins and tuna all depend on lower depths to survive.”

The BP oil spill is affecting the ecology of the Gulf in never before seen proportions, and will be responsible for mass casualties of wildlife. Dr. Nancy Rabalais, head scientist of the Louisiana Marine Consortium commented, “The magnitude and potential ecological damage is probably more great than anything ever seen in the Gulf of Mexico…Once it hits shoreline it’ll get into everything.”

Undersea oil is a major threat to both large and microscopic marine life, and is already threatening the existence of the brown pelican, the ridley and loggerhead sea turtles, whales, coral reefs and other organisms found in the deepwater habitat. The Gulf is also home to 207 species of saltwater fish, a large portion of which are sought for human consumption in addition to being key prey to other organisms in the food chain.

The spill is still relatively new, and many scenarios are being hypothesized. However, in late August 2010 a research expedition will be led by Dr. Michael Roman of the University of Maryland Center for Environmental Science to better examine the spill’s implications on marine life.

The deepwater ocean is the world’s largest habitat, giving the oil spill the largest area for ecological damage possible. Despite the already high monetary and socio-economic costs the spill has caused the United States and BP, it’s ecological damage has the potential to be the most enduring.

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