Marine mammal deaths from BP Deepwater Horizon disaster vastly underestimated

March 29, 2011 (ScienceBlog) – The Deepwater Horizon oil spill of 2010 devastated the Gulf of Mexico ecologically and economically. However, a new study published in Conservation Letters reveals that the true impact of the disaster on wildlife may be gravely underestimated. The study argues that fatality figures based on the number of recovered animal carcasses will not give a true death toll, which may be 50 times higher than believed. “The Deepwater oil spill was the largest in US history, however, the recorded impact on wildlife was relatively low, leading to suggestions that the environmental damage of the disaster was actually modest,” said lead author Dr Rob Williams from the University of British Columbia.”This is because reports have implied that the number of carcasses recovered, 101, equals the number of animals killed by the spill.” The team focused their research on 14 species of cetacean, an order of mammals including whales and dolphins. While the number of recovered carcasses has been assumed to equal the number of deaths, the team argues that marine conditions and the fact that many deaths will have occurred far from shore mean recovered carcasses will only account for a small proportion of deaths. To illustrate their point, the team multiplied recent species abundance estimates by the species mortality rate. An annual carcass recovery rate was then estimated by dividing the mean number of observed strandings each year by the estimate of annual mortality. The team’s analysis suggests that only 2% of cetacean carcasses were ever historically recovered after their deaths in this region, meaning that the true death toll from the Deepwater Horizon disaster could be 50 times higher than the number of deaths currently estimated. …

Whale and dolphin death toll during Deepwater disaster may have been greatly underestimated