The effects of oil exposure and weathering on black-needle rush (Juncus roemerianus) marshes along the Gulf of Mexico.

Oil exposure has been shown to be detrimental to several salt marsh plants however little information is available for Juncus roemerianus. Thirty-two mesocosms were established with J. roemerianus sod and replicate marshes were exposed to Louisiana sweet crude oil to test oil dose (6, 12, and 24 L m⁻²) and weathering (oil weathered for 0 days, 3 days, and 3 weeks). Juncus were monitored following oil exposure for culm survival, photosynthetic rates, and C-assimilation rates. Oil dosage had a significant effect among wetlands with low-dose (6 L m⁻²) mesocosms having higher culm survival, photosynthetic rates, and C-assimilation rates than medium or high dose wetlands (12 or 24 L m⁻²). Oil weathering did not elicit significant differences between treated wetlands however full strength wetlands (un-weathered oil) consistently had the lowest culm survivorship, photosynthetic rates, and C-assimilation rates. From our results, J. roemerianus marshes may be very susceptible to oil exposure.