Phytoremediation of small-scale oil spills in fresh marsh environments: a mesocosm simulation

Research was conducted to assess the impact of oiling on fresh-marsh plant communities and to test the efficacy of techniques that may be used to enha nce the bioremediation of crude oil spills in these environments while mini mizing secondary anthropogenic impacts. To emulate field conditions, a meso cosm facility was used that houses 120 mesocosm vessels, each of 200-1 capa city. A five-way factorial treatment arrangement was used that included two substrates (inorganic, organic), two nutrient regimes (fertilized, not fer tilized), two aeration levels (substrate aeration, no aeration), three oili ng concentrations (0-, 5-, 10-l m(-2) of South Louisiana Sweet Crude oil). and four vascular plant species (Alternanthera philoxeroides, Panicum hemit omon, Phragmites australis, Sagittaria lancifolia, and an unplanted control ). Under the 5- and 10-l m(-2) oiling concentrations, S. lancifolia display ed a short-term response of increased productivity, whereas P. hemitomon ha d the highest biomass production and photosynthetic rates at the end of the 18-month experiment. Overall plant growth and productivity. as well as oil degradation, were significantly higher in the inorganic substrate, indicat ing that biodegradation of oil spills in organic substrates may require a l onger time period. Time-released fertilizer also stimulated plant productiv ity and resulted in higher soil respiratory quotients, suggestive of greate r microbial activity, particularly in aerated mesocosms. The amount of oil remaining after 18 months was lowest in aerated and fertilized mesocosms co ntaining either P. hemitomon or S. lancifolia and a substrate of low organi c matter content. (C) 2001 Elsevier Science Ltd. All rights reserved.