By James A. Gibbs 

BP’s ill-fated Deepwater Horizon venture, having already spewed more than 2 million barrels of crude oil into the Gulf, is by far the largest oil spill in U.S. waters, dwarfing the 260,000 barrels released from the Exxon Valdez in Alaska’s Prince William Sound in 1989.  Estimates are that by the time BP’s two relief wells pump cement into the runaway well, as much as 3 million barrels of oil may have been lost. 

The costs to date are horrific, both to humans and to sea creatures.  Lives were lost, a huge drilling rig destroyed, businesses closed, workers displaced, economies of coastal areas devastated, millions of barrels of oil needlessly wasted, and the marine environment disrupted. Ahead for BP will be years of litigation, billions of dollars in fines and reparations, and perhaps ultimate bankruptcy.  The future for the company and its stockholders seems dim.

Nevertheless, science and the history of previous oil spills can provide some insights into the future of the waters of the Gulf of Mexico and our oceans in general.   Most obvious is that the oceans are highly resilient and can absorb major spills of crude oil with little long-term negative effect. 

There have been many major oil spills in the past, many of which were in the Gulf of Mexico.  I lived in Houston during WWII, and our family occasionally visited the beaches along Galveston Island. I remember seeing gallon jugs of kerosene set all along the beaches, partly to treat jelly-fish stings, but also to rinse off smudges from ever-present tar balls in the waves and on the shore.  Soon after the war the tar balls disappeared and only occasionally appeared again. Only recently did I learn that during the five month period between May and September 1942, when German U-Boats were most active in the Gulf, an estimated 1 million barrels of oil escaped from tankers and other vessels they sank.  Oil from scuttled tankers was the likely despoiler of Galveston’s beaches.

The giant spill of Pemex’s Ixtoc blowout well off Mexico’s Yucatan Peninsula in 1979 dumped an estimated 3.3 million barrels into the Gulf.  Fears were then, as now, that the Gulf would sustain permanent damage from the spill.  Some Mexican oil did wash ashore onto the beaches of Texas and other Gulf states, but much of the oil was destroyed by natural processes before reaching shore. The incident has already been largely forgotten or ignored. 

The Exxon Valdez spill has been one of the most intensively studied events of our time.  If we look at the long term effect of that spill we find that of the total amount of oil:

  • 50% biodegraded in the water.
  • 20% evaporated via atmospheric photolysis.
  • 14% was recovered for use.
  • 13% sank and became sub-tidal sediments.
  • 1% dispersed in the local waters.
  • 2% remains on or in the beaches

Concern at the time was that oil would permanently impair salmon populations and subsequent harvests.  Millions of dollars were paid to fishermen whose livelihoods were threatened.  Yet two years after the spill the salmon harvest in Prince William Sound was one of the largest ever recorded.

In general we should anticipate the same with the BP spill.  The good news from this data is that in the warmer waters of the Gulf of Mexico we can expect to see more of the oil biodegraded than in the cold Arctic waters.  This is because the micro organisms that eat the oil and the artificial seeding of the Gulf with more microbes will speed up the process.

Crude oil is, after all, a completely organic product, created through time by the deaths of multitudes of tiny plants and animal organisms. Their remains fell to the ocean floor and were fortuitously preserved from immediate destruction by a combination of factors, including burial by sediments that covered them and served as a shield from further destruction. Through time the effects of deeper burial, earth’s natural heat, and pressure from subsequent layers of sediments converted the organic residue to oil and natural gas. Thus, in a sense, crude oil is simply oceanic compost.

When crude oil is released into open waters, it is immediately attacked by microbes that are already present and that thrive on such organic matter.  Microbes have long enjoyed such fare, having developed a taste for it over the millennia as provided to them from natural oil and gas seeps in the ocean basins. Estimates of natural seepage rates into the world’s oceans are based on many assumptions, but range from 1.4 to 14.3 million barrels per year (3,900 to 39,000 barrels per day.  In the early 1990s, Texas A&M conducted a survey and documented 185 natural seeps in the Gulf of Mexico. Seepage in the Gulf of Mexico alone is estimated at about 1 million barrels per year (2,800 barrels per day.)

Of course, petroleum in the sea comes from a variety of sources.  The National Research Council of the National Academies in Washington D.C. published a report in 2003 entitled Oil in the Seas III – Inputs, Fates and Effects. It concluded that:

  • Most of the petroleum hydrocarbons in the sea worldwide (48% of the total) come from natural seeps.
  • 72% of the petroleum hydrocarbons discharged in the sea worldwide that have been caused by the impact of man (anthropogenic) come from petroleum consumers.  Unconcerned motorists contribute much of the total by pouring used oil from their vehicles directly into storm drains, which provide ready access to streams, lakes and oceans.     
  • The group that causes the second most anthropogenic petroleum hydrocarbons in the marine environment are the petroleum transporters  -  such as pipelines and tankers  -  that account for 22.5% of the anthropogenic worldwide total.
  • The group that pollutes the least is the group involved in petroleum extraction – the oil and gas production companies.  They account for 3% of the total worldwide petroleum hydrocarbon discharge, and 5.6% of the discharge caused by man.  Unquestionably there’s room for improvement.

BP is obviously at fault for the current disaster and must face the consequences. The public’s outrage will keep the attention of the press, politicians and lawyers focused on the unfolding consequences for many years.  Perhaps the most helpful activity for all of us is to be more mindful of the petroleum products we use each day, and strive to reduce the residues that could end up in the seas as tar ball mementos of our hydrocarbon fueled lifestyles.