Methanol is a common pollutant in freshwater ecosystems due to its widespread use in industrial operations, fuel, antifreeze, paints, and insecticides, and being a result of the burning of garbage. As a bioindicator species, Daphnia magna health indicates changes in aquatic ecosystem health. They are an important part of the food web, eating algae, and as a food source to insects and fish. No previous studies have examined the effects of the pollutant methanol on Daphnia heart function and mortality. This experiment examined the effects of varying methanol concentrations on heart function and mortality of Daphnia magna. It was hypothesized that methanol significantly affects the heart and mortality rate of Daphnia. Fifteen experimental biospheres were used in each trial, with three jars for each of the five concentrations. The biospheres were filled with deionized water and methanol in concentrations of 0 ppm (control), 822.6 ppm, 1644.5 ppm, 3289.0 ppm, 7119 ppm. In a second trial, the concentrations were 0 ppm, 822.6 ppm, 1644.5 ppm, 205.7 ppm, and 411.3 ppm. Heart and mortality rates were observed and recorded for each trial over 4-8 days. For each jar, videos were recorded for 15 seconds each and heart rate was counted, and mortality counted every other day. Based on the survival and heart rate differences, it was concluded that as methanol concentrations increase, the heart rate of Daphnia varied but didn’t respond linearly to concentration levels. Additionally, higher concentrations of methanol negatively affect survivability, although the initial control groups had somewhat high death rates. This study highlights the negative impact of methanol pollution on Daphnia because a negative impact on Daphnia affects the whole freshwater ecosystem. Indeed, in Lake Washington, Daphnia represent a major source of nutrients for juvenile Sockeye Salmon, making Daphnia indispensable for their growth.