Freshwater ecosystems will likely become sinks for future silver loadings as a result of increased nanosilver (n-Ag) use in industrial and commercial applications. A series of bioassays was performed to assess how n-Ag toxicity may be influenced by abiotic factors associated with natural freshwater ecosystems. Additionally, these bioassays provide insight into how environmentally relevant concentrations of n-Ag may sublethaly affect the freshwater benthic gastropod, Physa acuta, that plays pivotal roles in maintaining the structure and function of freshwater ecosystems. In sediment with no benthic organic carbon (BOC), gastropod vital rates decreased in treatments containing any n-Ag, gastropods in sediment with relatively low BOC appeared to trade off growth for reproduction at high n-Ag treatments, while gastropod vital rates in high BOC sediment remained unaffected at all nanosilver treatments. Sediment type may abate nanosilver toxicity as a result of organic carbon content. Effects of n-Ag on gastropod vital rates were not dependant on pH, suggesting aqueous pH does not directly influence n-Ag toxicity. Nanosilver (0.2 μg/L) stressed gastropods, altering their growth and reproduction tradeoff dynamics. Nanosilver concentrations modeled to exist in natural freshwaters, disrupted gastropod ability to detect and respond to a natural predator, while greater n-Ag concentrations stimulated gastropods to exhibit contaminant avoidance behavior and thereby attempted to flee their habitat. This study provides direction in understanding how adverse n-Ag effects may be influenced by abiotic parameters, while assessing sublethal effects of n-Ag on freshwater gastropods that are likely to occur in natural freshwater ecosystems, given current estimates of environmental n-Ag concentrations. / Department of Biology