Lake Miyajimanuma is a well-known stopover for numerous migrating white-fronted goose （Anser albifrons）. In this study, we monitored the quality of the influent, effluent, and water of Lake Miyajimanuma for 2 years, from 2011 to 2012, to investigate the trophic status and pollutant fluxes through the lake. Based on the phosphorus flux, we also estimated the contribution of goose excretion to eutrophication. Results suggest that Lake Miyajimanuma is highly eutrophic, and that total nitrogen （TN） and total phosphorous （TP） concentrations varied seasonally, corresponding with the visiting goose populations. TN and TP loads in the effluent were greater than in the influent to the lake, which suggests that excretion from the geese is a significant source of nutrients. Phosphorous fluxes from the influent and waterfowl excretion were estimated at 1.20-1.67 and 4.40-5.34 g m-2 y-1, respectively. These loads are sufficiently large to cause eutrophication of Lake Miyajimanuma. Our study indicates that, to alleviate the eutrophic conditions, the phosphorous load should be reduced both by dispersing the goose population and restoring the nutrient status of the whole catchment.