LEE DEB 9706317 Research will examine the effect of plants, both native and transgenically modified species, their rhizosphere communities and microbial mats on the bioremediation of sediments contaminated with high levels of mercury and PCBs. The project will include studies to: characterize (chemically, physically and biologically) the contaminated sediments; establish salt marsh and brackish water systems in mesocosms using the recently constructed Bioremediation and Environmental Research Mesocosm (BERM) facility at Skidaway Institute; evaluate various manipulative strategies for their affect on the accumulation and transformation of contaminants by plants growing in the mesocosms; and, test the most promising strategies from the mesocosms studies in the field. The results of the research should begin to establish a more complete understanding of the roles of various ecosystem components on bioremediation under field conditions as well as test the utility of selected transgenic species for their use as part of a multi-component bioremediation methodology.