Cultural eutrophication is the process whereby a body of water becomes over-enriched with nutrients, in particular nitrogen (N) and phosphorus (P), resulting in algal blooms and subsequent death and decomposition which deplete oxygen levels in the water (i.e. hypoxia), leading to the loss of aquatic animals (e.g. fishes). This is caused by excess N and P. Agriculture is the major source to Irish rivers and estuaries, with 70% of P loads and 82% of N loads attributed to agricultural sources . Hypoxia in the Gulf of Mexico has been linked to excessive N loading. Nuisance algal blooms in Lake Erie have been linked to agricultural P. Previous efforts have concentrated on measuring agricultural runoff directly using grab samples or spot measurements, but high frequency sampling will be essential to accurately characterize the extent and temporal resolution of agricultural impacts. Low cost real-time nutrient sensors are critical for quantifying the influence of agriculture on freshwater, and more broadly, for effective water management throughout Irish, European, and American river basins.