Factors controlling the impacts of south Louisiana crude oil on the vegetation and revegetation of coastal wetlands.

摘要

The impacts of south Louisiana crude oil on three types of marsh, salt, brackish, and freshwater, dominated by Spartina alterniflora, S. patens, and Sagittaria lancifolia, respectively, were studied in the greenhouse. The influence of a number of factors such as marsh type, plant species, oil dosage, oil coverage, soil composition, leaf surface structure, season and meteorological conditions, on the impact of crude oil to marsh vegetation and revegetation were investigated. Vegetative sensitivity to south Louisiana crude oil increased in the order of S. lancifolia, S. alterniflora, and S. patens. Photosynthetic rates, stem densities, and the regrowth of aboveground biomass for the two Spartina species significantly decreased, while those for S. lancifolia were either not detrimentally affected or enhanced by oil dosages up to 241 mg m{dollar}sp{lcub}-2{rcub}{dollar}. Sagittaria lancifolia showed relative resistance to oil coverage because its smooth cuticle on the leaf surface prevented oil from absorbing into internal tissue. However, the two Spartina species were sensitive to oil coverage of their aerial portions, with decreased live and total biomass production and stem density. Oil absorbed into the furrows on the adaxial surface of the two Spartina species completely inhibited their photosynthetic capabilities. However, oil contact with the lower aerial portions of the stems did not cause long-term damage to any of the species studied. In contrast, oil incorporation into the substrate caused both short and long term damages to all three plant species, with a reduction in photosynthetic rate, biomass, stem density and regrowth. Furthermore, all three plants species were affected by oil application to soil with high organic matter and coarse texture. The influence of season was dramatic. Sagittoria lancifolia and Spartina alterniflora were very resistant to applications of crude oil to the substrate during the fall, but they were least resistant in the summer. Vegetative transplants could be effectively used to revegetate oil contaminated soil with oil concentrations as high as 250 mg g{dollar}sp{lcub}-1{rcub}{dollar}. Fertilizer increased the biomass of the transplants in the oiled soil, and it also increased the oil degradation rate, suggesting that fertilization could be a valuable tool for restoring oil contaminated marshes.