GAINESVILLE, Fla. --- The BP Deepwater Horizon oil spill temporarily worsened existing manmade problems in Louisiana's salt marshes such as erosion, but there may be cause for optimism, according to a new study.
A study appearing online Monday 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 and this plant die off resulted in a more-than-doubled rate of erosion along the marsh edge and subsequent permanent marsh habitat loss. Vegetation farther from shore was relatively untouched by the incoming oil.
"Louisiana is already losing about a football field worth of wetlands every hour, and that was before the spill," said Brian Silliman, a University of Florida biologist and lead author of the study. "When grasses die from heavy oiling, their roots, that hold the marsh sediment together, also often die. By killing grasses on the marsh shoreline, the spill pushed erosion rates on the marsh edge to more than double what they were before. Because Louisiana was already experiencing significant erosive marsh loss due to the channelization of the Mississippi, this is a big example of how multiple human stressors can have additive effects."
Marshes are the life's blood of coastal Louisiana because they act as critical nurseries for the shrimp, oysters and fish produced in these waters while helping to sequester significant amounts of carbon. They also protect coastlines from flooding and guard estuarine waters from nutrient pollution.
But the marshes have been suffering for decades as a result of the channelization of the Mississippi River, which has starved them from needed sediments to deter erosion.
Then came the oil spill.
Researchers observed minimal oil on the surfaces of grasses located more than 45 feet from the shoreline, indicating that significant amounts of oil did not move into interior marshes.
|Contact: Brian Silliman|
University of Florida