BATON ROUGE, La. — A scientific study has found that heavily oiled areas in Barataria Bay showed twice the normal land erosion rates in the year and a half after the massive BP oil leak in 2010.
The Advocate reports the study found oil killed marsh plants and that led to the higher rates of erosion. However rates of erosion returned to more normal levels after about a year and a half, the study found.
The study was published Monday in the Proceedings of the National Academy of Sciences.
Brian Silliman, associate professor of biology at the University of Florida and lead author of the study, said the normal rate of 5 feet per year of erosion in the bay shoreline doubled to 10 feet per year.
The study found that after a year and a half, healthy marsh started to grow again along the shoreline and once roots took hold the erosion rates went back to pre-leak rates.
“It was a temporary event,” Silliman said.
The erosion rates went up when oil covered the marsh grass and the rhizomes, or underground stems that shoot out roots, died. A stem had to be covered heavily in oil for it to actually die, Silliman said. When oil got into the soil, it’s likely the oil’s toxicity also killed the rhizomes underground, he said.
“Once those rhizomes die, those gripping roots are not holding together the sediment anymore,” Silliman said.
The marshes were eroding before the spill because they are starved of sediment, but the oil spill brought additional stress, he said.
The study also found that most of the oiling was kept to the front of the shoreline within the first 15 to 30 feet. He said the tall marsh grass kept the concentration of oil on the perimeter.