As marsh plants recover from the Deepwater Horizon oil spill in Louisiana, so have the tiny plants and animals living in the soil, according to a new study published in Marine Ecology Progress Series.
But, not everything is back to normal following the 2010 disaster.
Researchers, who wanted to get a sense of how the marsh would recover from the largest oil spill in U.S. history, found that even in oiled areas that initially showed much lower numbers of soil organisms and plant life, plants recovered followed by the animals.
“The little critters are responding to the plants. They’re following what the plants are doing,” said John Fleeger, professor emeritus in LSU’s Department of Biological Sciences and lead author of the recently published article. “It’s really gratifying to see how resilient the marsh is.”
The years of study took place in the northern part of Barataria Bay. Researchers, including several from LSU, sampled 21 sites over time, studying an equal number of heavily oiled, moderately oiled and non-oiled sites.
The plants help with the recovery of the small organisms by providing shade, reducing the flow of water and providing a source of food.
Since these tiny plants and animals live in the soil and form a base for the coastal marsh food web, it’s possible to use them as an indicator of marsh health.
In most places, the marsh grass was recovering within two to three years to a point where they matched the growth in test areas where oil was not found.
Moderately oiled sites had about 1.5 times more plants and tiny animals than sites with no oil during the first two to three years before leveling out. Perhaps some plants didn’t recover as quickly so the marsh grass took up the slack, or the oil stressed the plants and the plants compensated by growing faster.
“Many of the animals did recover in three years, but not everything,” Fleeger said.
Some slightly larger soil invertebrates haven’t had the same response as the microscopic animals.
“There’s a lot of optimism there, but to say we have recovery after three years isn’t complete,” Fleeger said.
The monitoring continues at the 21 sites to determine how long it might take to see full recovery.
In addition, the team started a small-scale restoration study in 2014 by planting marsh grass in heavily oiled areas where there has been no recovery to determine if it’s possible to jump-start the process.
Another part of the team is working on a study of erosion in areas where the marsh was heavily polluted with oil. Those results haven’t been released.
The work was paid for through the Gulf of Mexico Research Initiative — a 10-year program that hands out grants to researchers studying the impacts of the spill. The initiative is funded through a $500 million allocation from BP.
Follow Amy Wold on Twitter, @awold10.