The effect of a louisiana crude oil discharge from a pipeline break on the vegetation of a Southeast Louisiana brackish marsh

A pipeline break on 23 April 1985 near Nairn, Louisiana, resulted in the release of approximately 300 barrels of Louisiana crude oil into a brackish marsh dominated by a vegetative mixture of Spartina patens, S. alterniflora and Distichlis spicata. Since the impact of oil spills on brackish marshes has received little attention, we initiated this investigation to assess the post-spill status of the vegetation. Sixty-eight randomly selected plots located on 15 transects which traverse the complete study area were sampled for various vegetative cover parameters. The major impact of the spill was confined to the 50-acre (20-ha) marsh located immediately around the pipeline rupture. The oil caused a 64% reduction in live vegetative cover (adjusted for differences in total percentage cover among plots) in this marsh 3 months after the spill. This high plant mortality from a relatively low oil dosage (estimated at 0·28 liters/m²) was probably due to the contact of the oil with a large percentage (about 30–70%) of the photosynthetic leaf surfaces of the vegetation and the penetration of the oil into the marsh substrate.