Most studies concerning the impact of tropospheric ozone on biological systems pertain to terrestrial systems exposed to elevated ozone levels. Research on the effects of ozone on aquatic systems has been limited to its use as an alternative disinfectant in wastewater treatment facilities. These studies have focused on the oxidation of organic material by ozone, its effects on bacteria and viruses within the wastewater, the retention time or half-life of ozone in water and the solubility of ozone in water. Since local tropospheric ozone levels continue to rise in many areas, the importance of ozone interactions with aquatic freshwater systems must be studied. The proposed work will further the knowledge of how elevated tropospheric ozone affects the aquatic ecosystem, specifically microbial and macroinvertebrate trophic interactions. Benthic macroinvertebrate communities play an important role in processing terrestrial carbon from leaf litter into forms more available to others trophic levels. Macroinvertebrates assimilate organic material that has been colonized and broken down via microbial organisms, making biomass more available to other organisms within the aquatic food web. Hence, disturbances that affect the macroinvertebrate communities may cascade through the system. Previous work has suggested that ozone has detrimental effects on microbial colonization and the quality and availability of dissolved organic matter within the system. Since macroinvertebrates form many trophic levels that rely on these basal resources, elevated ozone may indirectly impact community structure through effects on microbial communities and dissolved organic carbon.