First sign of 2010 deepwater horizon oil found in sparrows

BATON ROUGE, US: Researchers from the Louisiana State University (LSU) have recognised the first evidence of the 2010 Deepwater Horizon (DWH) oil spill in a land animal - the Seaside Sparrow.

The researchers studied the diet and feathers of sparrows collected more than a year after the oil spill. The birds that were captured in habitats that were exposed to the oil had a different chemical signature in their tissues than the birds that were found in areas of the marsh that were not exposed to the oil. The scientists’ results show that the oil from the Deepwater Horizon oil spill was incorporated into the prey and feathers of the exposed birds.

The Deepwater Horizon (DWH) oil spill that occurred on April 2010 in the Gulf of Mexico was a result of the explosion and sinking of the Deepwater Horizon oil rig. The rig was owned by an offshore drilling contractor, Transocean, and was rented to BP Plcfor exploration of the Macondo Prospect, an oil field off the coast of Louisiana.

This oil spill released thousands barrel of oil, gaseous hydrocarbons into the northern Gulf of Mexico over 87 days. It is estimated that some percent of the spilled oil was chemically dispersed, evaporated or dissolved or naturally dispersed.

This research is published in the journal Environmental Research Letters.

“We know that carbon from oil entered the offshore and nearshore food webs as demonstrated for plankton, fish and filter feeders. But this is the first demonstration that carbon from oil was also integrated into a terrestrial vertebrate species, the Seaside Sparrow,” said Sabrina Taylor, associate professor at school of renewable natural resources, LSU.

The Seaside Sparrow is a year-round resident of Louisiana marshes. This new study suggests that direct exposure to the toxic oil may have been detrimental to the birds’ reproductive success.

“These results suggest that the differences we have observed in sparrow gene expression and reproductive success between oiled and unoiled sites may be caused by direct toxicological effects not just habitat degradation or loss of prey species,” she said.

The researchers encourage additional studies on the effect of the oil spill on terrestrial species.

“We tend to think of terrestrial ecosystems as safe from oil contamination. However, the boundary between marine and terrestrial ecosystems is much less defined than we assume. Species that live at the boundary are not only vulnerable to the toxic effects of oil, but they can also be responsible for the transport of oil into the terrestrial food webs,” Andrea Bonisoli Alquati, a professor of environmental toxicology in the Department of Biological Sciences at Cal Poly Pomona and the lead author of the study.

“Future risk and damage assessments should incorporate an evaluation of the potential threat to terrestrial wildlife from oiling operations and oil spills,” added Alquati.

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