Study: BP spill doubled rates of land loss in oiled marsh

The BP Deepwater Horizon oil spill temporarily worsened erosion in Louisiana's salt marshes, according to a new study.

Researchers from the University of Florida, writing in the Proceedings of the National Academy of Sciences, found the 2010 spill killed off salt marsh plants 15 to 30 feet from the shoreline.

The study found the plant die off resulted in more than double the rate of erosion along the marsh edge and permanent land loss.

"When grasses die from heavy oiling, their roots that hold the marsh sediment together, also often die," wrote Brian Silliman, a biologist and the study's lead author.

However, Silliman's team found vegetation more than 45 feet from the shoreline was relatively untouched, indicating that significant amounts of oil did not move into interior marshes.

Instead, the researchers found that the tall grasses along the marsh edge acted as "wall-like trap to incoming oil slicks, concentrating oil on the marsh edge."

As plants along the shoreline died over a period of 18 months, the study found their roots holding tight to the sediment perished as well.

That exposed the shoreline to wave action "without the effect of the gripping plant roots."

Silliman's team found some encouraging results, including significant declines in the concentration of oil over 18 months.