Contact:	Howard Snell, snell@unm.edu Steve Carr, (505) 277-1821
June 6, 2002 UNM BIOLOGY PROFESSOR HELPS ESTABLISH CONNECTION BETWEEN OIL SPILL AND DEATH OF MARINE IGUANAS University of New Mexico Biology Professor Howard Snell, in collaboration with several other professors, has helped link the mortality of marine iguanas to an oil spill on the Galapagos island of Santa Fe. The research, titled “Marine Iguanas Die From Trace Oil Pollution” and published in the June 6 issue of Nature Magazine, establishes a link between the oil spill in January 2001 with a 62 percent mortality rate amongst the indigenous creatures the year after the “Jessica” oil tanker ran aground spilling approximately three million liters of diesel and bunker oil. “Our first impression was that the biological diversity of the Galapagos had largely escaped harm from the Jessica spill,” said Snell. “In general that is true, but the work with Martin Wikelski and his other colleagues has confirmed subtle effects that take a long time to develop and can have serious impacts for components of the Galapagos fauna.” Typically, the investigation of animal populations affected by environmental contamination usually begins following a spill in order to study the recovery process. But Snell, who spends spring semesters working at the Charles Darwin Foundation (CDF) in the Galapagos Islands as part of a collaborative agreement, and the foundation, was able to help Wikelski and other researchers who had accumulated long-term data sets on two island populations of marine iguanas. The combination of Wikelski’s accrued research and the detailed tracking of the spilled oil by Snell and the CDF-led team enabled the group to assess the effects of low-level oil contamination following the accident on Santa Fe island by comparing it with the other, unaffected habitat on Genovesa island. Also compared were the circulating levels of the stress hormone corticosterone in blood samples taken from the marine iguanas on Santa Fe immediately before and shortly after the oil spill. In an earlier paper, published in Science shortly after the spill, the researchers argued that exposed animals could suffer high mortality as a result of the increased stress suffered as a result of the spill. The Nature paper confirmed those predictions by documenting that mortality occurred. There were four possible explanations for the high mortality rate after the oil spill. The oil may have had a direct toxic effect either on the iguanas themselves or on the algae they consume, which is their main food source. The animals may have declined to eat because their food had been fouled or their vital hindgut microsymbionts may have been poisoned preventing the herbivorous iguanas from digesting their food. The results illustrate the severe effects that low-level environmental contamination can have on wild animal populations. The corticosterone levels are a reliable indicator of the life-threatening stress, which correlates with the high mortality rate suffered on Santa Fe island. “We previously thought that the primary threats to the conservation of the Galapagos were the combined effects of invasive species, over exploitation by a growing human population and terrestrial habitat alteration,” said Snell. “However, we’ve now found that large scale environmental pollution must also be dealt with. That’s a sad message for a remote archipelago six hundred miles out in the Pacific Ocean.” In addition to Snell, other professors involved in the research included Martin Wikelski, Vanessa Wong and Brett Chevalier of the Department of Ecology and Evolutionary Biology at Princeton University and Niles Rattenborg, Department of Psychiatry, University of Wisconsin Medical School. # # #

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