At least since the 1969 Santa Barbara blowout, we have tended to understand the environmental calamity of major spills through images of oiled wildlife lying dead or in agony along the shore. But animals whose bodies are recovered in a die-off are sometimes said to represent only “the tip of an iceberg”: simply the ones that, by chance, have stranded and been discovered and then reported to authorities. In the Exxon Valdez case, where serious impacts on killer whales, sea otters, and shorebirds took years to manifest themselves, the government came up with a multiplier to account for the numbers of undiscovered dead animals that the oil giant was liable for. In the Gulf of Mexico, the multiplier for some marine mammal species could be very high. According to a recent study, on average, only one in fifty whales and dolphins that die at sea are recovered on the Gulf’s shores.
For marine mammals, the most immediate danger from the Macondo spill was from oiling and inhaling toxic fumes, which can cause brain lesions, disorientation, and death. Going forward, the mechanisms of harm are subtler. As we have seen from the Exxon Valdez, oil can work up the food chain, accumulate in body tissue, induce cascade effects across an ecosystem, and impact wildlife populations for decades afterwards. For now, concern for marine mammals has centered on three particularly vulnerable species: bottlenose dolphins, sperm whales, and Bryde’s whales.
Life Goes On?
According to most biologists, the most disruptive of these activities are probably seismic surveys, the industry’s primary tool for offshore exploration in the Gulf and elsewhere, whose high-powered airguns regularly pound the water with sound louder than virtually any other man-made source save explosives. These surveys have a vast environmental footprint, disrupting feeding, breeding, and communication of some marine mammal and fish species over tens or in some cases even hundreds of miles. For the Gulf’s sperm whales, they mean less food: even moderate levels of airgun noise appear to seriously compromise the whales' ability to forage. In an average year, BOEMRE approves more than 60 seismic surveys in the northern Gulf, none of which has undergone review under the Marine Mammal Protection Act. No one knows how the cumulative impacts of this nearly constant disruptive activity will affect wildlife already compromised by the spill.
The Way Forward
• Congress and the Obama administration should adopt the recommendations of the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling.
• Congress should establish a research fund to ensure that vital research on Gulf marine mammals continues once Natural Resource Damage Assessment funds expire.
• The administration should strengthen mitigation requirements for seismic surveys and other activities that are currently impacting the same vulnerable species affected by the spill.