Gulf's future depends on oil-eating bacteria, lingering toxicity

Published 12 August 2010

Many marine bacteria have evolved to consume oil and other hydrocarbons, and now the spill has allowed these bacteria to follow their food beyond their natural habitat near oil seeps at the bottom of the Gulf; microbes may degrade the oil quickly, but their activity could eventually pose risks to the Gulf’s ecosystem, particularly in the deep ocean; scientists also worry about lingering toxicity — this is because oil’s toxic constituents, such as polycyclic aromatic hydrocarbons, can disrupt reproduction of marine organisms and can lower their offsprings’ vitality; this chronic toxicity will be magnified along the Gulf Coast’s beaches, salt marshes, and wetlands, because oil degradation in these sites will proceed at a much slower pace than in oxygen-rich environments

Gulf coast oil spill cleanup crew in hazmat protective clothing hunting for oil to clean up // Source: shelleytherepublican.com

The environmental impact of millions of gallons of oil still in the Gulf of Mexico from the Deepwater Horizon incident may depend on microscopic helpers: Bacteria that consume oil and other hydrocarbons and could break down the spilled crude, making it disappear. This is the topic of a detailed article by Charles Schmidt in the current issue of Chemical & Engineering News (C&EN), the American Chemical Society’s (ACS) weekly newsmagazine.

The article points out that the oil-eating bacteria are beneficial in helping to clear away the oil. Their activity, however, could eventually pose risks to the Gulf’s ecosystem, particularly in the deep ocean. The oil acts as a huge source of food and could produce bacteria “blooms,” or massive population explosions. As the blooms die and decay, they remove oxygen from the Gulf water, jeopardizing the health of fish and other aquatic animals.

The article discusses scientific research underway to shed light on the bacteria’s effects. It notes that the oxygen depletion so far is not as serious as the Gulf of Mexico’s infamous “dead zone,” an 8,000 square mile area — about the size of New Jersey — with oxygen levels too low for fish to survive (see “Largest-ever Gulf dead zone spans from Galveston to Mississippi River,” 5 August 2010 HSNW).

The Gulf’s oil plumes cause nearly a 35 percent oxygen drop compared to a 90 percent drop in that dead zone.

More highlights from Schmidt’s article:

  • After the 20 April explosion that sank the Deepwater Horizon exploration rig and started the largest marine oil spill in history, microbiologists converged on the Gulf to investigate the microbial composition throughout its waters and affected coastlines. According to Joel Kostka, a microbial ecologist at Florida State University, Tallahassee, the fundamental goals of this research are to determine the oil’s impact on the Gulf’s microbial ecosystems and to assess how limiting factors, chiefly oxygen concentrations, influence microbial oil degradation. Results may not only tell how fast the Gulf’s ecosystem will recover, Kostka says, but also provide scientists with information to help cleanup crews work efficiently.
  • Monitoring efforts have focused on drops in dissolved oxygen levels, a sign of microbial metabolism. Preliminary data show that marine microbes have mobilized across the Gulf and are, in fact, chewing their way through the oil plumes. For example, graduate students working with Andreas Teske, a marine biologist at the University