Oil doubles rate of loss in Louisiana marshes

Tuesday, 26 June 2012 10:07

News & Events - Engineering News

June 26, 2012

The economic impacts of the 2010 oil spill at BP's Deepwater Horizon have still yet to to be understood, much less the extent of the environmental damage. But PhysOrg reports a new study from the University of Florida offers an analysis of the impact the spill had on the region's crucial marshes.

Disappearing marsh economy

Louisiana has always been known for its huge marine economy, with massive fleets of fishing and shrimping boats, along with a major clamming industry. All of these industries are supported in large part by the dense marshes built up by the silt deposited at the mouth of the Mississippi river. The heavy grasses hold together the loose soil along the banks, making fertile grounds for clams and other shellfish while also providing an important carbon sink for the region.

However, this crucial environmental resource has been in steady decline for years thanks to changes made to the course of the Mississippi to help promote boat traffic on the river. The channelization of the Mississippi has prevented silt from upriver from being deposited on the marshes, leaving them to steadily erode under the constant assault of tidal currents.

"Louisiana is already losing about a football field worth of wetlands every hour, and that was before the spill," explained Brian Silliman, an assistant professor of biology at the University of Florida and the leader of the research team.

This marshland that washes away is effectively gone forever, since no soil is building up to replace it.

Tracking oil's impact

After the Deepwater Horizon oil well exploded in April 2010, spilling nearly 5 million barrels of oil into the Gulf of Mexico, huge quantities of oil washed up on the shore among these sensitive marshes, and Silliman's team set about tracking what impact the oil had on the region.

"[The oil] looked like a thick black belt on the shore line — it went on and on. You could see the grasses underneath the oil were dying and decaying," Silliman told the Post.

Surprisingly, the researchers found that the roughly 45 miles of marshland affected by moderate or heavy oil exposure actually proved relatively resistant to the spill, with the dense grasses serving to halt its advance and protecting the inner regions of the marsh, according to The Washington Post. In general, oil penetrated no further than 45 feet into the marshes.

However, the grasses that were oiled ultimately died, their roots breaking apart and further exacerbating the region's ongoing erosion problems. In heavily-oiled areas, the rate of erosion literally doubled to more than 10 feet per year.

Preventing further losses

The good news for the Louisiana marshlands is that regions that did not completely erode were quickly reclaimed by the well-preserved inner marshes, and the rate of erosion stabilized with the death of the oiled plants.

However, Bloomberg reports that BP has already received oil drilling leases in the area around the failed Deepwater Horizon rig. As offshore oil exploration continues to grow, it becomes increasingly important to invest in oil engineering research to help protect these sensitive ecological areas.

The Alaska Dispatch reports that one new bill put forward in the U.S. Senate, the Oil Spill Research and Technology Act of 2012, would put significant federal funding toward developing better systems to control oil spills, preventing them from ever reaching the shore.

However, the bill, introduced by Senator Maria Cantwell of Washington, would also require that research be targeted toward cleaning colder and icier areas, such as those along the Alaskan coast.