Just Gulfing, Gulfing

If you have taken Environmental Science then you know what a hypoxic zone is. If you haven’t then it’s also known as a dead zone because it can no longer support life. The Gulf of Mexico is one of these areas and it has only gotten worse since oil spill of April this year. The dead zone has been building over time as each spring and summer fertilizer from the fields of the U.S. Midwest runs off into the Mississippi River. It carries the nutrients down the length of the continent before dumping them into the Gulf of Mexico. Once they get there, the nitrogen and phosphorus explodes in a bloom in algae, phytoplankton and other microscopic plants. After the plants die they drift to the bottom and their decomposition sucks the oxygen out of the seawater. The result is a vast dead zone, lethal to sea life that cannot swim out of the way, in inhabitable waters near the Gulf Coast that is sometimes as large as the land mass of New Jersey and with the as much as 3.8 million liters of oil now spilling into the Gulf per day this will only get worse.

The oil spill may exacerbate the shallow-water dead zone through a bunch of physical and biological processes. But it could also help minimize the dead zone through similar means. Overall, the response of the Gulf dead zone to the oil spill is quite uncertain, with oxygen levels being tugged up and down by numerous factors, leaving the future of this habitat in question. At the same time, further from shore, the oil is having a host of potential oxygen-depleting effects from the surface waters all the way to the seafloor. So think about it: Will the oil spill create more dead zones in those deeper habitats? Or could it simply help to minimize the one we already have? Oil creates a slick that rides on the water’s surface. First and foremost, this physical coating prevents seawater from absorbing oxygen from the atmosphere. As the oil washes into ever-shallower waters, that barrier will particularly choke off oxygen in the estuaries and wetlands that serve as habitat and nurseries for much sea life, in essence asphyxiating larvae and other inhabitants.

Of course, the smaller Exxon Valdez oil spill never ended up creating such dead zones near shore. The 41.5 million liters of oil spilled off southern Alaska dropped oxygen levels in the water by as much as 50 percent but currents there minimized the damage to sea life, and the large-scale movements of seawater may work similarly in the Gulf. I thought reading this that only bad things were to come of this enormous oil spill however it appears that the introduction of this spill could help the giant spill at the expense of creating several other, smaller oxygen depeted zones.

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