Business Case

Business Case

Introduction

The Deepwater Horizon oil spill of 2010 created a new awareness of the potential impacts these types of events might have on the environment. Understanding how hydrocarbons and dispersants affect phytoplankton populations is a relevant issue because the structure and function of pelagic marine food webs depend on the energy and matter supplied by phytoplankton photosynthesis, a major pathway of mass and energy transfer in marine and aquatic environments. A pollutant that affects primary production has the potential to cause a trophic cascade that may alter the local food web. On April 20, 2010, the mobile offshore drilling unit Deepwater Horizon exploded in the northern Gulf of Mexico, releasing an estimated 780,000 cubic meters of Sweet Louisiana Crude (MC252) and 205,000 metric tons of methane over the next 86 days. Physical containment or removal of the spilled oil was not possible due to the physical limits of mechanical recovery equipment when dealing with light crude, which rapidly spreads too thin to be captured by mechanical methods and was impeded by weather. Therefore, all the issues and aspects related to Business Case will be discussed in detail.

Description of the Case

Biodegradation of hydrocarbons is limited by their low water solubility. Corexit contains surfactants that reduce interfacial tension between oil and water, promoting the formation of numerous micron sized oil droplets, which can be transported into the water column instead of floating on the surface, creating a slick. Waves and currents are necessary to effectively mix, disperse, and dilute the tiny oil droplets. In subsea application, the oil plume provides the turbulent energy required for mixing dispersant and oil. Following dispersion, oil droplets are exposed to a larger volume of seawater, therefore nitrogen and phosphorus from the seawater may be continually replenished around the oil droplets increasing availability of nutrients for the oil-degrading bacterial communities. Significant amounts of inorganic nitrogen and phosphorus are required for microbial degradation of hydrocarbons. The increase in the surface area to volume ratio of the spilled oil provides a greater opportunity for biodegradation by naturally occurring oil-degrading bacteria and dilution potentially decreases toxicity for all organisms. However, the application of dispersant increases the concentration of hydrocarbons in the water and this may offset any positive effect of dilution. Acute toxicity tests on invertebrates showed that the toxicity of oil and dispersed oil were about the same. Due to increased volatility of dispersed oil, exposure resulted in acute toxicity while oil alone caused chronic toxicity (Boué & Edgar, 2006).

Various Factors related to Case

A concentrated surface slick exposes organisms living at the ocean surface to very high concentrations of oil and also limits the diffusion of oxygen into the water column. The use of dispersant reduces tension between oil and water in the oil slick and removes it from the surface. Even though dispersant also increases the solubility of hydrocarbons, removal of the slick is important. Floating oil can limit gas exchange and reduce light penetration, causing decreases in primary production. If oil is removed from the ...