Oil Spill Killed Some Marsh Plants But Spared Others

Whether oiled marsh grasses live or die appears to be heavily dependent on species, according to a study in one of the areas hardest hit after the 2010 oil spill in the Gulf of Mexico (Environ. Sci. Technol., DOI: 10.1021/es203552p).

Marsh grasses are important because they hold soil, preventing land erosion, and because they act as nurseries for shrimp, fish, and other marine life. Understanding how they respond to oil could help guide efforts to clean up future spills.

Working at the northern end of Barataria Bay, about 30 miles southeast of New Orleans, Louisiana State University researchers studied two dominant marsh grasses for seven months after the Deepwater Horizon sank: Spartina alterniflora, also known as cordgrass, and Juncus roemerianus, or needlegrass. In spots hit with the most oil, almost everything died, as the researchers had expected. But in marsh areas where the oiling was moderate, the researchers found a distinctive pattern.

Juncus proved highly sensitive to oil when compared to Spartina: More Spartina plants survived and produced young shoots. By seven months after the spill began, the aboveground biomass of Spartina was similar in moderately oiled and unoiled marshes, while oiled Juncus had not recovered. “That was a surprise,” says lead author Quianxin Lin, of the differences in survival. Greenhouse experiments that mimicked the oiling conditions backed up the researchers’ field results.

Lin posits that Juncus may have fared worse in part because its leaves extend from the soil up, whereas Spartina’s leaves sit higher up and avoided more of the oil.

The team hopes to continue its field and greenhouse work to determine the causes of Spartina’s superior resilience.