I investigated water quality in an ecological context at two locations along the New River in southwest Virginia with similar land use, with the exception of being downstream and upstream of the Radford Army Ammunition Plant (RAAP). Freshwater macroinvertebrates at a low trophic level, such as Ephemeroptera (mayflies), are sensitive to environmental changes, making them known bioindicators, especially of heavy metals. I predicted that 1) water samples collected downstream of the RAAP will have greater concentrations of heavy metals and 2) nymphal mayflies collected downstream will exhibit decreased negative phototaxis responses and have a smaller length-mass ratio than nymphal mayflies collected upstream of RAAP. There is evidence to support that increased concentrations of some metals, such as iron and cadmium, can be correlated to changes in bioturbation and escape behaviors in mayflies. Additionally, it has been found that increased ion concentration may decrease growth rates in mayflies. Water samples were collected and analyzed for metal ion content using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), revealing increased downstream concentrations of Li, Mg, Ca, S, and Sr. I collected Heptageniidae, a common mayfly scraper, from upstream and downstream locations, then measured the negative phototaxis response by using a green light source to create a light intensity gradient in shallow water in an enclosed space in a lab environment. I measured the net distance that individual mayflies traveled along this gradient using manual video tracking. I found that sampling location was not a significant factor in distance traveled. The length and mass of the mayflies were measured and showed that mayflies from upstream were less massive per length and I found regression constants using a power law model. Relationships from both locations agreed with published length-mass relationships. I failed to reject some parts of the alternative hypothesis, but showed differences in length-mass relationship that may suggest lower biomass in the downstream location. The study suggests greater investigation into the physiological and ecological effects of manufacturing discharge on key aquatic macroinvertebrates.