Dolphins are struggling to survive in the Gulf of Mexico seven years after the explosion on the Deepwater Horizon oil rig, an international study involving researchers at the University of St Andrews has concluded.
In April 2010 a blowout on the drilling rig resulted in the release of 134 million gallons of oil into the Gulf of Mexico over an 87-day period, killing thousands of marine mammals including bottlenose dolphins.
A new study coordinated by the US National Oceanic and Atmospheric Administration (NOAA) documents the unprecedented mortality rate and long-term environmental impacts of the oil’s exposure and represents a synthesis of more than five years’ worth of data collection, analysis and interpretation.
The study found that the dolphin population in the Barataria Bay area of the Gulf of Mexico will have reduced by 50% within the decade following the spill and that full population recovery will take 40 years. In addition, the scientists found that 25% of the current population are underweight and 17% are in a poor or grave condition.
Professor Ailsa Hall of the School of Biology at St Andrews and Director of SMRU was an expert advisor on the Deepwater Horizon Natural Resource Damage Assessment (NRDA). She said: “My assistance was required to provide advice in relation to how assessing the damage to the bottlenose dolphins and large whales that inhabit the Gulf of Mexico and that were exposed to the oil should be tackled.
“My research expertise as a marine mammal epidemiologist and toxicologist was sought to provide independent critical review of the proposed work. I was therefore able to provide analytical input into the scientific approach taken by the NOAA scientists, to overview their research plans and to assist in interpreting their findings.
“The challenges faced by the NOAA scientists in determining whether the oil had caused significant effects on the health and survival of the dolphins and whales in the Gulf of Mexico was immense.”
Dr Len Thomas of the School of Mathematics and Statistics at the University and Director of CREEM said: “CREEM worked as part of a large team to predict the long-term damage to marine mammal populations from the oil spill. Our first challenge was to integrate multiple sources of information from the relatively well-studied dolphin populations around the Mississippi delta to assess the current population health and predict how this might change in the future.
“The second challenge was how to deal with the many other dolphin populations, and other species in the Gulf, about which much less is known.
“CREEM specialises in the development and application of statistical methods for complex ecological datasets, and this certainly fit the bill.
“Despite all the uncertainties, it is clear that many populations of marine mammal were badly affected by the oil spill, and that these negative effects will persist for many years into the future.”