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

► We used 32 mesocosms with Juncus roemerianus sod to examine wetland oil exposure. ► We examined the influence of oil dose and weathering on J. roemerianus. ► Oil dosage had an effect on J. roemerianus survival, photosynthetic rate, and C-assimilation rates. ► Oil weathering showed no statistical effect on plant survival, photosynthetic rate, and C-assimilation.