The Gulf of Mexico Oil Spill: Fate and Behavior

We welcome a guest post today from Stan Ulanski, author of The Gulf Stream: Tiny Plankton, Giant Bluefin, and the Amazing Story of the Powerful River in the Atlantic. After the deadly explosion on an oil rig off the coast of Louisiana last week, thousands of gallons of oil started pouring into the waters of the Gulf of Mexico. We turned to Ulanski to find out what kind of environmental effects we may see from this spill. This is his response.–ellen

Oil is undeniably the lifeblood of an industrialized society, but the increasing demand for oil within the global market has led to more drilling in what many consider environmentally sensitive areas. As thousands of gallons of oil continue to gush daily from the crippled oil rig in the Gulf of Mexico, scientists, politicians, and businessmen are keeping a watchful eye on where the oil will go and what its impact will be on the environment.

Crude oil is a complex mixture of hydrocarbons, some chemically light in composition and others heavy. The progression, duration, and fate of the oil depends on the nature of the oil itself, the parameters of the actual oil spill, and environmental conditions. The intricate processes of oil transformation in the marine environment start developing almost immediately after the oil’s contact with seawater.

The most immediate and visible result of the Gulf of Mexico’s oil spill is the resultant slick, which has spread over an ever increasing area of the gulf. Though an oil slick will usually drift in the same direction as the wind, the impact of waves and currents must also be factored in when assessing the slick’s movement. One grave concern is that the oil could get caught up in the Loop Current, a robust, clockwise circulation that extends northward into the Gulf of Mexico and flows along the Florida peninsula before exiting through the Straits of Florida. From there, the oil be could be picked up by the northward flowing Gulf Stream, making its way all along Florida’s east coast. In the path of this migrating river of oil are coral reefs, which are extremely sensitive to some of the toxic oil components.

Further changes occur in the oil slick under the combined influence of meteorological and oceanographic factors. In particular, the slick thins over time and upon reaching a critical thickness of about 0.1 mm, will disintegrate into separate fragments that spread over larger and most distant areas. This ominous result will directly influence containment and cleanup efforts. The oil may also interact with the seawater to form an emulsified mixture that can exist in the marine environment for over 100 days in the peculiar “chocolate mousse.” This gooey mess, if it reaches the coast, will coat the beaches and endanger wildlife, such as sea birds and turtles.

Some of the oil may aggregate in the form of petroleum lumps, or tar balls, which can be found both in the coastal waters and on beaches. These unsightly deposits degrade slowly, existing for a month or up to a year.

Most oil compounds are water soluble to a certain degree, especially the low-molecular-weight hydrocarbons. The dissolution that occurs in the water column could negatively impact planktonic organisms–microscopic to small drifting organisms that have no means of escaping the advancing oil. Since these plants and animals are the foundation of the Gulf of Mexico’s marine food chain, providing food and nourishment for higher level organisms, the effect on commercial and recreational fisheries could be disastrous.

But there is hope in that the marine ecosystem destroys, metabolizes, and deposits some of the oil, transforming it into more common and safer substances. Up to 10 to 30 percent of the oil may be adsorbed on suspended material and deposited to the bottom. Because the Gulf States have a wide and shallow continental shelf where particulates are abundant and mixing robust, sedimentation will be vigorous. Also, the fate of many petroleum compounds in the marine environment is ultimately controlled by microbial activity. About a hundred known species of bacteria and fungi are able to use oil components to sustain their growth and metabolism. This process known as biodegradation can play a vital role in neutralizing the overall impact of this disastrous spill.

Stan Ulanski
James Madison University
author of The Gulf Stream: Tiny Plankton, Giant Bluefin, and the Amazing Story of the Powerful River in the Atlantic