Question

Following the Deepwater Horizon accident in the Gulf of Mexico in 2010, bioremediation was used to eliminate much of the oil from the contaminated water. To encourage the growth of oil-degrading microbes, "fertilizer" including iron and nitrogen was added to the water. Which of the following statements regarding the growth of these microbes is incorrect?

A. The concentration of sulfate in the Gulf of Mexico is sufficient for the growth of oil-degrading microbes.
B. Large amounts of iron were needed, as iron is a macronutrient for oil-degrading microbes.
C. Nitrogen gas (N2) present in air is not in a form that can be used by oil-degrading microbes.
D. The oil-degrading microbes used oil (hydrocarbons) as their carbon source.

Answer 1

The incorrect statement is about iron being a macronutrient for oil-degrading microbes. In bioremediation of oil spills, nutrients like nitrogen and phosphorus are added as fertilizers to encourage the growth of microbes that use oil as their carbon source.

Step-by-step explanation:

The incorrect statement among the ones provided would be 'B. Large amounts of iron were needed, as iron is a macronutrient for oil-degrading microbes.' Iron, although essential, is generally required in smaller amounts and is considered a micronutrient rather than a macronutrient for microbes which rely more on macronutrients such as carbon, nitrogen, and phosphorus to sustain significant growth.

In an oil spill scenario, measure such as the utilization of bioremediation techniques are critical. The addition of nutrients like nitrogen must be in a readily usable form, as atmospheric nitrogen (N2) is not directly usable by most microorganisms. The added nutrients act as a fertilizer to stimulate the growth of native oil-degrading bacteria, which utilize the oil as their carbon source for growth and energy. This process is enhanced by bacteria like Alcanivorax borkumensis, which produce surfactants that help solubilize the oil to hasten the degradation process.

It is important to note that while sulfate is indeed typically present in seawater in sufficient concentrations for microbial growth, in the case of the Gulf of Mexico, it was the addition of nitrogen and phosphorus that was primary to support the bioremediation process.