We are at the two-year anniversary of the BP oil spill, and some recent accounts paint a pretty bleak picture of the state of the Gulf of Mexico. The immediate impacts on what "matters most" to humans (e.g., fisheries) are plentiful. Tainted seafood, carcinogenic compounds and blackened beaches have all had negative impacts on fisheries and human health in the region. But what about basic biology? Will the ecosystems of the Gulf ever resemble their former selves? Although comprehensive reports for ecosystem damage are still forthcoming, the long-term effects from the last major oil spill (which was much smaller than the BP spill and in a much more contained area) don't provide much assurance.
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The Exxon Valdez oil spill in Prince William Sound on March 23, 1989, made worldwide headlines for its immediate impact on wildlife. More than 40 million litres of oil spilled into the remote sound, devastating populations of mammals, fish, birds and invertebrates. Despite the fact that it's been over two decades, many ecosystems have not recovered. A report from February 2012 highlights the fact that negative effects of the Exxon Valdez spill remain devastatingly clear. Sea otters and other near-shore dwelling organisms have yet to show solid evidence of population recovery1. Residual oil continues to accumulate in sheltered bays and shorelines, which is where many bird and otter species find their food. Sea otters excavate foraging pits to find their main sustenance, clams. In disturbing the sediments, the otters release oil that continues to linger there, increasing their exposure to carcinogens. Oil clings to their fur and is ingested during grooming. In addition, the clams themselves are a veritable sink for carcinogens in the sediments, so otters are experiencing oil exposure on multiple levels.
Research on otter populations in the Knight Island Archipelago2 shows that there is temporal variation in the oil-exposure potential, which provides further clues as to why populations are not recovering. Exposure is greatest during the late spring when female otters remain close to the shore to give birth. Small pups are born into an environment that is contaminated with Exxon oil, which is certainly contributing to the lack of recovery of the species as a whole. Newborn pups have few mechanisms to avoid or dispense of the oil — they are sitting ducks.
More than 20 years after the Exxon Valdez spill, humans in the western world have yet to curb their gas-guzzling ways. Part of me thinks that this is because Prince William Sound is so remote. It's easy for us to forget about the damaging oil when it's in a far-away place that most of us have not or will not ever experience first-hand. The Gulf oil spill is completely different — the spill was over 17 times greater than the Exxon spill, and the oil is in an area that millions of people see, feel, smell, taste and touch daily. Maybe in some odd way this is a good thing. Perhaps having a massive oil spill in our own backyard is what it will take for people to realize that blame for an oil spill should not just go to BP or Exxon, but to all of us.
1 Monson DH, Doak DF, Ballachey BE, Bodkin JL (2011) Could residual oil from the Exxon Valdez spill create a long-term population 'sink' for sea otters in Alaska? Ecological Applications 21:2917-2932
2 Bodkin JL, Ballachey BE, Coletti HA, Esslinger GG, Kloecker KA, Rice SD, Reed JA, Monson DH (2012) Long term effects of the 'Exxon Valdez' oil spill: sea otter foraging in the intertidal as a pathway of exposure to lingering oil. Marine Ecology Progress Series 447: 273-287.