Sunday, April 17, 2011

Marine Mammals and the BP Oil Spill: Much More Deadly Than Touted?

Less than 12 months ago, on April 20th, 2010, an explosion on the Deepwater Horizon oil drilling rig killed 11 men and released huge amounts of crude oil—estimated to about 4.9 million barrels—into the Gulf of Mexico. What followed seemed like endless weeks of frustration and panic over the spreading endangerment of a huge ecosystem, as oil flowed unabated from a damaged wellhead. Concerns over a devastating economic and environmental impact for the region could not be overstated, and images from the Exxon Valdez oil spill in 1989, with its apocalyptic destruction of marine life in the area, came flooding back to the nation’s consciousness.

And such images began to circulate again. But the efforts of BP and related companies, the U.S. and state governments, and concerned citizens from all over the country seemed to minimize the worst of the damage. Marine life—especially that of mammals such as porpoises, whales and dolphins—was felt to be minimally impacted given the huge scale of the spreading oil.  A study by the National Oceanic and Atmospheric Administration (NOAA) maintained that the number of cetacean (whale, dolphin, porpoises and other similar marine mammals) carcasses registered was modest compared to widespread fears.  The total cetacean death count was only 101. 

However, this last March, a group of concerned scientists from all over the world wrote an article published in Conservation Letters that directly disputed the NOAA’s figures, calling them grossly underestimated.  In the article, entitled Understanding the damage: interpreting cetacean carcass recoveries in the context of the Deepwater Horizon/BP incident, (Understanding the damage: interpreting ceacean carcass recoveries in the context of the Deepwater Horizon/BP incident) they used analyses garnered from past oil spill disasters to estimate the marine mammal deaths of the BP oil spill of last year.  The difference in numbers estimated—when compared with the NOAA’s study—was of a factor of 50 times. 

The NOAA study, the scientists said, presumed that the total number of dead cetaceans were simply the number of carcasses counted, with no attempt to extrapolate upwards to a more likely figure.  Even after the Exxon Valdez spill, it was widely accepted that the large number of registered deaths was only a small portion of the presumed dead.  

Looking at a past analysis of cetaceans in the Gulf of Mexico, it was estimated that there were about 4,500 deaths from all causes (natural or otherwise) from 2003 to 2007.  Yet during that same period, only 17 carcasses were discovered, a rate of .4%.  (Reasons for such a low carcass number are varied, but the most common are the sinking of the carcasses, their deterioration, or their simply being blown out to sea and uncountable by investigators.)  Working with that percentage, the scientists felt that the true number of cetacean deaths from the BP oil spill would most likely approach over 5,000—a huge disparity when compared with the NOAA’s numbers. 

The scientists worried in particular that certain subgroups of larger populations will be hit particularly hard, not just in the number of their members dying, but in the long-term effects for the survivors as well.  A year after the Exxon Valdez spill in 1989, more than 40% of a killer whale group had died; but even more ominous is the fact that there has been no reproduction in that group in all of the years since.   And herring stocks seemed to bounce back a year after the Exxon Valdez spill, only to collapse completely four years later.  The long-term repercussions in such disasters are simply unknown.

There is great concern in particular for the sperm whale.  Of the 21 protected marine mammals that inhabit the Gulf, the sperm whale is one of six on the Endangered Species List.  They number only 1,500, and live their whole lives within the Gulf’s limits.  As the oil spill originated from the bottom of the sea floor—instead of being spilled on top of it—the oil is thought to have contaminated every water level, and thereby much of the fish that the sperm whale feeds upon.  The toxins concentrated in the fish would become even more concentrated in the whales preying upon them, and the resulting risk to the sperm whale population as a whole is plainly evident. 

Making matters worse, scientists trying to study recovered carcasses in hopes of better understanding the effects of the spill are being stymied by the federal government itself.  Of particular interest was the spike this year in bottle-nosed dolphin deaths—especially among calves—and whether or not it was connected to last year’s spill.  Their attempts to collect data from government-contracted investigators, and those investigators’ desire to share that same data, was met with a mandated gag-order by the National Marine Fisheries Service (NMFS.)  The NMFS told its investigators to keep all of their findings confidential, as the information being collected could be used in criminal proceedings against various companies related to the spill.  This frustrated the scientific community greatly, as similar gag-orders during the Exxon Valdez spill proved unnecessary, and only slowed much-needed fact-finding.  They felt that the same pointless mistakes are being made again.

The scientists that contributed to Underestimating the damage believed that long-term observation of the cetacean populations was highly necessary.  Otherwise, chronic effects of the spill on surviving members would go unstudied, and scientists’ ability to forecast the dangers of future events would be hampered.  Although they admitted that the actual number of deaths would never be known for sure, they feared that the unreasonably low numbers of deaths cited would make the situation seem less dire, and needed funding would be diverted elsewhere. 

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