Coastal Fish in Gulf of Mexico Recover After Oil Spill

Populations of coastal fish along the Gulf of Mexico seem to be relatively unscathed after the 2010 Deepwater Horizon oil spill, according to recent research published in the international online journal PLoS ONE.

The research comes as a joint effort from marine ecologists at the University of South Alabama and the University of North Carolina at Chapel Hill, who discovered that there has actually been an increase in the number of juveniles found in at least 12 of the 20 species of coastal fish studied since the disaster occurred.  Overall, the species-by-species catch rates of coastal fish recorded within a five-year data set went from (1,080±43 fishes km-towed−1 [μ ± 1SE]) in 2006 to (1,989±220 fishes km-towed−1 [μ ± 1SE]) in 2010.

This increase appears despite the fact that vulnerable larvae have been exposed to oil-polluted water, which contains toxic contaminants such as polycyclic aromatic hydrocarbons (PAHs).  PAHs are known to result in genetic damage and physical deformities, and can alter or delay the developmental onset of adulthood in fish eggs/larvae.  These same PAHs are responsible for causing sickness and even death amongst workers involved in the aftermath of the oil-spill clean up efforts.

For many, including the researchers themselves, this news comes as a surprise, considering that the explosion at Deepwater Horizon caused the largest accidental marine oil spill in the history of the petroleum industry–reportedly 20 times greater than the Exxon Valdez oil spill in Alaska in 1989.  Between the months of April and July 2010, the collapsed drilling rig gushed 4.4 million barrels of crude oil at a rate of 53,000 barrels a day over a protracted 84 day period.  In addition to spilled oil fouling hundreds of miles of sea water, the initial explosion at the Macondo Prospect killed 11 workers, with many more hospitalizations of local residents and workers occurring during clean-up efforts due to high levels of exposure to dangerous carcinogens.

The researchers suspect that the main reason these coastal fish have avoided catastrophe is due to the fact that much of the oil released did not rise to the surface; instead, it emulsified at the well head and throughout the water column, allowing the majority of spawning coastal fish to become resilient enough to survive the oil’s effects.

Other factors may also be contributing to the apparent stability of these coastal fish populations, including a reduction in the number of major predators who eat their juvenile fish and larvae, which is also a result of the oil spill.  Coastal fish species may also be uniquely resilient to oil pollution “due to their mobility or foraging ecology.”  Lastly, a release from harvest pressure due to fishing bans in about one-third of the Gulf after the oil spill may account for increased spawning activity, although no significant statistics were found to prove this.

Even though researchers admit that “these data provide reason for early optimism,” the good news should be taken with a grain of salt, in that “attention should now turn to possible chronic effects of oil exposure on fishes,” as well as any “delayed indirect effects” which may not be seen until years after oil exposure.  Such was the case with the Exxon Valdez oil spill of 1989, which resulted in Alaskan coastal wildlife being exposed to residual sub-lethal levels of toxic oil up to 20 years after the initial incident.

In the case of Deepwater Horizon, the early concern over the Gulf of Mexico’s coastal ecosystems will likely shift towards a long term study of the spilled oil’s effects in the the deep ocean, where the majority of it is found today.

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